title: Predicting \tau-lepton polarization at the LHC

abstract:
  This is a master's thesis and it is written in Lithuanian language.
  The goal of this thesis is to predict the polarization of a \tau-particle
produced at the LHC and coming from a real W boson. This is achieved by
calculating the projection of the expectation value of the polarization vector
of the \tau-particle. Calculations are done in the frame of the Standard Model.
In this model only left-chiral currents couple to W bosons. The mass of the
\tau-particle is left non-zero, therefore one can see the influence of helicity
mixing on polarization.
  The initial colliding particles at the LHC are protons and the most important
channels for W production are quark fusion: $q\bar{q} -> W^+ -> \tau^+
\nu_{\tau}$. Calculation for \tau-lepton production from Z bosons and photons,
$q\bar{q} -> Z^0, A^\gamma -> \tau^+ \tau^-$, are also included for
investigation of possible background events. Because quarks are confined in a
proton, this thesis presents a thorough treatment on discribing proton's inner
structure with Parton distribution functions.
  The results section shows plots of differential cross sections for
\tau-lepton production from different quark flavours and different energy
intervals of the \tau-particle. A projection of the expectation value of the
polarization vector depends on the chosen energy intervals. The vector on which
it is projected is chosed to be the direction of the \tau-particle's motion.
The influence of the mass is best seen for low energy particles, because then
the helicity mixing is higher.
  PACS numbers: 13.88.+e, 14.60.Fg


title:
On the cross-section of Dark Matter using substructure infall into
  galaxy clusters

abstract:
  We develop a statistical method to measure the interaction cross-section of
Dark Matter, exploiting the continuous minor merger events in which small
substructures fall into galaxy clusters. We find that by taking the ratio of
the distances between the galaxies and Dark Matter, and galaxies and gas in
accreting sub-halos, we form a quantity that can be statistically averaged over
a large sample of systems whilst removing any inherent line-of-sight
projections. In order to interpret this ratio as a cross-section of Dark Matter
we derive an analytical description of sub-halo infall which encompasses; the
force of the main cluster potential, the drag on a gas sub-halo, a model for
Dark Matter self-interactions and the resulting sub-halo drag, the force on the
gas and galaxies due to the Dark Matter sub-halo potential, and finally the
buoyancy on the gas and Dark Matter. We create mock observations from
cosmological simulations of structure formation and find that collisionless
Dark Matter becomes physically separated from X-ray gas by up to 20h^-1 kpc.
Adding realistic levels of noise, we are able to predict achievable constraints
from observational data. Current archival data should be able to detect a
difference in the dynamical behaviour of Dark Matter and standard model
particles at 6 sigma, and measure the total interaction cross-section sigma/m
with 68% confidence limits of +/- 1cm2g^-1. We note that this method is not
restricted by the limited number of major merging events and is easily extended
to large samples of clusters from future surveys which could potentially push
statistical errors to 0.1cm^2g^-1.


title: The Approximate Capacity Region of the Gaussian Y-Channel

abstract:
  A full-duplex wireless network with three users that want to establish full
message-exchange via a relay is considered. Thus, the network known as the
Y-channel has a total of 6 messages, 2 outgoing and 2 incoming at each user.
The users are not physically connected, and thus the relay is essential for
their communication. The linear-shift deterministic Y-channel is considered
first, its capacity region is characterized and shown not to be given by the
cut-set bounds. The capacity achieving scheme has three different components
(strategies): a bi-directional, a cyclic, and a uni-directional strategy.
Network coding is used to realize the bi-directional and the cyclic strategies,
and thus to prove the achievability of the capacity region. The result is then
extended to the Gaussian Y-channel where the capacity region is characterized
within a constant gap independent of the channel parameters.


title: Transition-Edge Sensors for Particle Induced X-ray Emission Measurements

abstract:
  In this paper we present a new measurement setup, where a transitionedge
sensor detector array is used to detect X-rays in particle induced X-ray
emission measurements with a 2 MeV proton beam. Transition-edge sensors offer
orders of magnitude improvement in energy resolution compared to conventional
silicon or germanium detectors, making it possible to recognize spectral lines
in materials analysis that have previously been impossible to resolve, and to
get chemical information from the elements. Our sensors are cooled to the
operation temperature (65 mK) with a cryogen-free adiabatic demagnetization
refrigerator, which houses a specially designed X-ray snout that has a vacuum
tight window to couple in the radiation. For the best pixel, the measured
instrumental energy resolution was 3.06 eV full width at half maximum at 5.9
keV.We discuss the current status of the project, benefits of transition-edge
sensors when used in particle induced X-ray emission spectroscopy, and the
results from the first measurements.


title: Cooperativity of a few quantum emitters in a single-mode cavity

abstract:
  We theoretically investigate the emission properties of a single-mode cavity
coupled to a mesoscopic number of incoherently pumped quantum emitters. We
propose an operational measure for the medium cooperativity, valid both in the
bad and in the good cavity regimes. We show that the opposite regimes of
subradiance and superradiance correspond to negative and positive
cooperativity, respectively. The lasing regime is shown to be characterized by
nonnegative cooperativity. In the bad cavity regime we show that the
cooperativity defines the transitions from subradiance to superradiance. In the
good cavity regime it helps to define the lasing threshold, also providing
distinguishable signatures indicating the lasing regime. Increasing the quality
of the cavity mode induces a crossover from the solely superradiant to the
lasing regime. Furthermore, we verify that lasing is manifested in a wide range
of positive cooperative behavior, showing that stimulated emission and
superradiance can coexist. The robustness of the cooperativity is studied with
respect to experimental imperfections, such as inhomogeneous broadening and
pure dephasing.


title:
Analytical coexistence of s, p, s + p phases of a holographic
  superconductor

abstract:
  We analytically study the critical phase of a mixed system of the U(2) gauge
fields and global symmetry on the boundary using gauge/gravity. A variational
minimization problem has been formulated. The numerical results pertinently
show that there exists a minimum chemical potential in which both scalar
(s-wave) and vector (p-wave) condensates exist in a mixture, as well as in the
distinct s- and p-phases. This result is obtained by breaking the symmetry into
U(1) symmetry and rotational symmetry. While the analytical solutions of
condensates and charge densities are achieved in both cases: the balanced and
unbalanced holographic superconductors. This is the first an- alytical study of
the coexistence of two modes of the superconductivity with different order
parameters. The realistic model consists of two different phases of the
superfluidity in Helium.


title: On strong homotopy for quasi-schemoids

abstract:
  A quasi-schemoid is a small category with a particular partition of the set
of morphisms. We define a homotopy relation on the category of quasi-schemoids
and study its fundamental properties. As a homotopy invariant, the homotopy set
of self-homotopy equivalences on a quasi-schemoid is introduced. The main
theorem enables us to deduce that the homotopy invariant for the quasi-schemoid
induced by a finite group is isomorphic to the automorphism group of the given
group.


title: Markov chain approximations to scale functions of L\'evy processes

abstract:
  We introduce a general algorithm for the computation of the scale functions
of a spectrally negative L\'evy process $X$, based on a natural weak
approximation of $X$ via upwards skip-free continuous-time Markov chains with
stationary independent increments. The algorithm consists of evaluating a
finite linear recursion with its (nonnegative) coefficients given explicitly in
terms of the L\'evy triplet of $X$. Thus it is easy to implement and
numerically stable. Our main result establishes sharp rates of convergence of
this algorithm providing an explicit link between the semimartingale
characteristics of $X$ and its scale functions, not unlike the one-dimensional
It\^o diffusion setting, where scale functions are expressed in terms of
certain integrals of the coefficients of the governing SDE.


title:
Fast creation of conditional quantum gate and entanglement using a
  common bath only

abstract:
  We propose a scheme to for fast conditional phase shift and creation
entanglement of two qubits that interact with a common heat bath. Dynamical
decoupling is applied in the scheme so that it works even in the regime of
strong interaction between qubits and environment. Our scheme does not request
any direct interaction between the two qubits.


title: Quasilocal Conserved Charges with a Gravitational Chern-Simons Term

abstract:
  We extend our recent work on the quasilocal formulation of conserved charges
to a theory of gravity containing a gravitational Chern-Simons term. As an
application of our formulation, we compute the off-shell potential and
quasilocal conserved charges of some black holes in three-dimensional
topologically massive gravity. Our formulation for conserved charges reproduces
very effectively the well-known expressions on conserved charges and the
entropy expression of black holes in the topologically massive gravity.


title:
Modification of the formation of high-Mach number electrostatic
  shock-like structures by the ion acoustic instability

abstract:
  The formation of unmagnetized electrostatic shock-like structures with a high
Mach number is examined with one- and two-dimensional particle-in-cell (PIC)
simulations. The structures are generated through the collision of two
identical plasma clouds, which consist of equally hot electrons and ions with a
mass ratio of 250. The Mach number of the collision speed with respect to the
initial ion acoustic speed of the plasma is set to 4.6. This high Mach number
delays the formation of such structures by tens of inverse ion plasma
frequencies. A pair of stable shock-like structures is observed after this time
in the 1D simulation, which gradually evolve into electrostatic shocks. The ion
acoustic instability, which can develop in the 2D simulation but not in the 1D
one, competes with the nonlinear process that gives rise to these structures.
The oblique ion acoustic waves fragment their electric field. The transition
layer, across which the bulk of the ions change their speed, widens and their
speed change is reduced. Double layer-shock hybrid structures develop.


title: Evidence for the suppressed decay B^- -> DK^-, D -> K^+\pi^-\pi^0

abstract:
  We report a study of the suppressed decay B^- -> DK^-, D -> K^+\pi^-\pi^0,
where D denotes either a D^0 or a \bar{D}^0 meson. The decay is sensitive to
the CP-violating parameter \phi_3. Using a data sample of 772 x 10^6 B\bar{B}
pairs collected at the \Upsilon(4S) resonance with the Belle detector, we
measure the ratio of branching fractions of the above suppressed decay to the
favored decay B^- -> DK^-, D -> K^-\pi^+\pi^0. Our result is R_{DK} = [1.98 +/-
0.62(stat.) +/- 0.24(syst.)] x 10^{-2}, which indicates the first evidence of
the signal for this suppressed decay with a significance of 3.2 standard
deviations. We measure the direct CP asymmetry between the suppressed B^- and
B^+ decays to be A_{DK} = 0.41 +/- 0.30 (stat.) +/- 0.05 (syst.). We also
report measurements for the analogous quantities R_{D\pi} and A_{D\pi} for the
decay B^- -> D\pi^-, D -> K^+\pi^-\pi^0.


title:
UV to far-IR reflectance spectra of carbonaceous chondrites. I.
  Implications for remote characterization of dark primitive asteroids targeted
  by sample-return missions

abstract:
  We analyze here a wide sample of carbonaceous chondrites from historic falls
(e.g. Allende, Cold Bokkeveld, Kainsaz, Leoville, Murchison, Murray and
Orgueil), and from NASA Antarctic collection in order to get clues on the role
of aqueous alteration in promoting the reflectance spectra diversity evidenced
in the most primitive chondrite groups. We particularly focus in the
identification of spectral features and behavior that can be used to remotely
identify primitive carbonaceous asteroids. The selected meteorite specimens are
a sample large enough to exemplify how laboratory reflectance spectra of rare
groups of carbonaceous chondrites exhibit distinctive features that can be used
to remotely characterize the spectra of primitive asteroids. Our spectra cover
the full electromagnetic spectrum from 0.2 to 25 microns by using two
spectrometers. First one is a UV-NIR spectrometer that covers the 0.2 to 2
microns window, while the second one is an Attenuated Total Reflectance IR
spectrometer covering the 2 to 25 microns window. In particular, laboratory
analyses in the UV-NIR window allow obtaining absolute reflectance by using
standardized measurement procedures. We obtained reflectance spectra of
specimens belonging to the CI, CM, CV, CR, CO, CK, CH, R, and CB groups of
carbonaceous chondrites plus some ungrouped ones, and allows identifying
characteristic features and bands for each class, plus getting clues on the
influence of parent body aqueous alteration. These laboratory spectra can be
compared with the remote spectra of asteroids, but the effects of terrestrial
alteration forming (oxy)hydroxides need to be considered.


title: Study of gamma cascades of 59Ni by thermal neutron reaction

abstract:
  The quantum properties are important to study nuclear structure. The energy,
spin, parity, transition order are usually interesting to research. In this
experiment, 59Ni is activated by thermal neutron on 3rd horizontal channel of
Dalat nuclear Reactor.


title: The Spectrum of Light States in Large N Minimal Models

abstract:
  $W_{N,k}$ minimal models possess an interesting class of `light' primaries
which control much of the low energy density of states in the large $N$ 't
Hooft limit. In this paper we conduct a detailed exploration of their
distribution using a combination of numerical and analytical techniques. We
also make some observations about the density of states of the full CFT. Our
results appear to support the contention that there is no finite temperature
analogue of the Hawking-Page transition in these systems.


title:
Fourier coefficients of degree 2 Siegel-Eisenstein series with trivial
  character at squarefree level

abstract:
  We compute the Fourier coefficients of all degree 2 Siegel-Eisenstein series
of square-free level $N$ transforming with the trivial character. We then apply
use these formulae to present some explicit examples of higher representation
numbers attached to non-unimodular quadratic forms.


title:
Offline and Online Incentive Mechanism Design for Smart-phone
  Crowd-sourcing

abstract:
  In this paper, we consider the problem of incentive mechanism design for
smart-phone crowd-sourcing. Each user participating in crowd-sourcing submits a
set of tasks it can accomplish and its corresponding bid. The platform then
selects the users and their payments to maximize its utility while ensuring
truthfulness, individual rationality, profitability, and polynomial algorithm
complexity. Both the offline and the online scenarios are considered, where in
the offline case, all users submit their profiles simultaneously, while in the
online case they do it sequentially, and the decision whether to accept or
reject each user is done instantaneously with no revocation. The proposed
algorithms for both the offline and the online case are shown to satisfy all
the four desired properties of an efficient auction. Through extensive
simulation, the performance of the offline and the online algorithm is also
compared.


title: Elements of a unified framework for response formulae

abstract:
  We provide a physical interpretation of the first and second order terms
occurring in Ruelle's response formalism. We show that entropy fluxes play a
major role in determining the response of the system to perturbations. Along
this line, we show that our framework allows one to recover a wealth of
previous results of response theory in both deterministic and stochastic
contexts. In particular, we are able to shed light on the crosslinks between
the dynamical systems approach \'{a} la Ruelle and large deviations methods.


title: Dyonic Black Hole and Holography

abstract:
  We study thermodynamic properties of dyonic black hole and its dual field
theory. We observe that the phase diagram of a dyonic black hole in constant
electric potential and magnetic charge ensemble is similar to that of a Van der
Waals fluid with chemical potential. Phase transitions and other critical
phenomena have been studied in presence of magnetic charge and chemical
potential. We also analyse magnetic properties of dual conformal field theory
and observe a ferromagnetic like behavior of boundary theory when the external
magnetic field vanishes. Finally, we compute susceptibility of different phases
of boundary CFT and find that, depending on the strength of the external
magnetic field and temperature, these phases are either paramagnetic or
diamagnetic.


title:
Stochastic homogenization of viscous Hamilton-Jacobi equations and
  applications

abstract:
  We present stochastic homogenization results for viscous Hamilton-Jacobi
equations using a new argument which is based only on the subadditive structure
of maximal subsolutions (solutions of the "metric problem"). This permits us to
give qualitative homogenization results under very general hypotheses: in
particular, we treat non-uniformly coercive Hamiltonians which satisfy instead
a weaker averaging condition. As an application, we derive a general quenched
large deviations principle for diffusions in random environments and with
absorbing random potentials.


title: Split Supersymmetry Under GUT and Current Dark Matter Constraints

abstract:
  We recalculate the two-loop beta functions for three gauge couplings taking
into account all low energy threshold corrections in split supersymmetry
(split-SUSY) which assumes a very high scalar mass scale M_S. We find that, in
split-SUSY with gaugino mass unification assumption and a large M_S, the gauge
coupling unification requires a lower bound on gaugino mass. Combined with the
constraints from the dark matter relic density and direct detection limits, we
find that split-SUSY is very restricted and for dark matter mass below 1 TeV
the allowed parameter space can be fully covered by XENON-1T(2017).


title:
Charge Trapping Dynamics in PbS Colloidal Quantum Dot Photovoltaic
  Devices

abstract:
  The efficiency of solution-processed colloidal quantum dot (QD) based solar
cells is limited by poor charge transport in the active layer of the device,
which originates from multiple trapping sites provided by QD surface defects.
We apply a recently developed ultrafast electro-optical technique, pump-push
photocurrent spectroscopy, to elucidate the charge trapping dynamics in PbS
colloidal-QD photovoltaic devices at working conditions. We show that IR
photo-induced absorption of QD in the 0.2-0.5 eV region is partly associated
with immobile charges, which can be optically de-trapped in our experiment.
Using this absorption as a probe, we observe that the early trapping dynamics
strongly depend on the nature of the ligands used for QD passivation while it
depends only slightly on the nature of the electron-accepting layer. We find
that weakly bound states, with a photon-activation energy of 0.2 eV, are
populated instantaneously upon photoexcitation. This indicates that the
photogenerated states show an intrinsically bound-state character, arguably
similar to charge-transfer states formation in organic photovoltaic materials.
Sequential population of deeper traps (activation energy 0.3-0.5 eV) is
observed on the ~0.1-10 ns time scales, indicating that most of carrier
trapping occurs only after substantial charge relaxation/transport. The
reported study disentangles fundamentally different contributions to charge
trapping dynamics in the nanocrystal-based optoelectronic devices and can serve
as a useful tool for QD solar cell development.


title:
Dust in the wind I: spectropolarimetric signatures from disk-born
  outflows

abstract:
  In this first research note of a series of two, we conduct optical/UV
investigations of the spectropolarimetric signatures emerging from the
structure of quasars (Elvis 2000) applied to a purely theoretical, dusty model.
We aim to explore the similarities/differences between an absorbing, disk-born
outflow and the usual dusty torus that is supposed to hide the internal regions
of active galactic nuclei (AGN). Using radiative transfer Monte Carlo
simulations, we compute the continuum polarization signatures emerging from the
model setup of Elvis (2000). We find that a dust-filled outflow produces very
low amount of wavelength-depend polarization degrees, associated with a photon
polarization angle perpendicular to the projected symmetry axis of the model.
The polarization percentages are ten times lower than what can be produced by a
toroidal model, with a maximal polarization degree found for intermediate
viewing angle (i.e. when the observer's line-of-sight crosses the outflowing
material). The structure for quasars unsuccessfully blocks the radiation from
the central irradiating source and shows a spectropolarimetric behavior that
cannot be conciliated with observations. Either a new set of morphological
parameters or different optical thickness must be considered.


title:
Quantum Monte Carlo study of the dynamic structure factor in the gas and
  crystal phase of hard-sphere bosons

abstract:
  We investigate the dynamic structure factor of a system of Bose particles at
zero temperature using quantum Monte Carlo methods. Interactions are modeled
using a hard-sphere potential of size $a$ and simulations are performed for
values of the gas parameter $na^3$ ranging from the dilute regime up to
densities $n$ where the thermodynamically stable phase is a solid. With
increasing density we observe a crossover of the dispersion of elementary
excitations from a Bogoliubov-like spectrum to a phonon--maxon--roton curve and
the emergence of a broad multiphonon contribution accompanying the
single-quasiparticle peak. In particular, for $na^3=0.2138$, which corresponds
to superfluid $^4$He at equilibrium density, the extracted spectrum turns out
to be in good agreement with the experimental energy--momentum dispersion
relation in the roton region and for higher momenta. The behavior of the
spectral function at the same density in the stable solid and metastable gas
phase above the freezing point is also discussed.


title:
Charge-Transfer State Dynamics Following Hole and Electron Transfer in
  Organic Photovoltaic Devices

abstract:
  The formation of bound electron-hole pairs, also called charge-transfer (CT)
states, in organic-based photovoltaic devices is one of the dominant loss
mechanisms hindering performance. While CT state dynamics following electron
transfer from donor to acceptor have been widely studied, there is not much
known about the dynamics of bound CT states produced by hole transfer from the
acceptor to the donor. In this letter, we compare the dynamics of CT states
formed in the different charge-transfer pathways in a range of model systems.
We show that the nature and dynamics of the generated CT states are similar in
the case of electron and hole transfer. However the yield of bound and free
charges is observed to be strongly dependent on the HOMOD-HOMOA and LUMOD-LUMOA
energy differences of the material system. We propose a qualitative model in
which the effects of static disorder and sampling of states during the
relaxation determine the probability of accessing CT states favourable for
charge separation.


title:
Structural manipulation of the graphene/metal-interface with Ar+
  irradiation

abstract:
  Controlled defect creation is a prerequisite for the detailed study of
disorder effects in materials. Here, we irradiate a graphene/Ir(111)-interface
with low-energy Ar+ to study the induced structural changes. Combining computer
simulations and scanning-probe microscopy, we show that the resulting disorder
manifests mainly in the forms of intercalated metal adatoms and vacancy-type
defects in graphene. One prominent feature at higher irradiation energies (from
1 keV up) is the formation of line-like depressions, which consist of
sequential graphene defects created by the ion channeling within the interface
-- much like a stone skipping on water. Lower energies result in simpler
defects, down to 100 eV where more than one defect in every three is a graphene
single vacancy.


title:
High frequency trading and asymptotics for small risk aversion in a
  Markov renewal model

abstract:
  We study a an optimal high frequency trading problem within a market
microstructure model designed to be a good compromise between accuracy and
tractability. The stock price is driven by a Markov Renewal Process (MRP),
while market orders arrive in the limit order book via a point process
correlated with the stock price itself. In this framework, we can reproduce the
adverse selection risk, appearing in two different forms: the usual one due to
big market orders impacting the stock price and penalizing the agent, and the
weak one due to small market orders and reducing the probability of a
profitable execution. We solve the market making problem by stochastic control
techniques in this semi-Markov model. In the no risk-aversion case, we provide
explicit formula for the optimal controls and characterize the value function
as a simple linear PDE. In the general case, we derive the optimal controls and
the value function in terms of the previous result, and illustrate how the risk
aversion influences the trader strategy and her expected gain. Finally, by
using a perturbation method, approximate optimal controls for small risk
aversions are explicitly computed in terms of two simple PDE's, reducing
drastically the computational cost and enlightening the financial
interpretation of the results.


title: A Deep and Tractable Density Estimator

abstract:
  The Neural Autoregressive Distribution Estimator (NADE) and its real-valued
version RNADE are competitive density models of multidimensional data across a
variety of domains. These models use a fixed, arbitrary ordering of the data
dimensions. One can easily condition on variables at the beginning of the
ordering, and marginalize out variables at the end of the ordering, however
other inference tasks require approximate inference. In this work we introduce
an efficient procedure to simultaneously train a NADE model for each possible
ordering of the variables, by sharing parameters across all these models. We
can thus use the most convenient model for each inference task at hand, and
ensembles of such models with different orderings are immediately available.
Moreover, unlike the original NADE, our training procedure scales to deep
models. Empirically, ensembles of Deep NADE models obtain state of the art
density estimation performance.


title: GENIUS: Generating Usable User Interfaces

abstract:
  In this report we describe the implementation and approach developed during
the GENIUS Project. The GENIUS project is about the generation of usable user
interfaces. It tries to cope with issues related to automatic generation where,
usually end-user complain about the poor quality (in term of usability) of
generated UI. To solve this issue GENIUS relies on Model-Driven Engineering
principles and several MDE tools. Notably, it consists in a set of metamodels
specific to the interaction, a set of model transformation embedding usability
criteria and an environment for model execution/ interpretation.


title:
The Role of Driving Energy and Delocalised States for Charge Separation
  in Organic Semiconductors

abstract:
  The electron-hole pair created via photon absorption in organic
photoconversion systems must overcome the Coulomb attraction to achieve
long-range charge separation. We show that this process is facilitated through
the formation of excited, delocalized band states. In our experiments on
organic photovoltaic cells, these states were accessed for a short time (<1ps)
via IR optical excitation of electron-hole pairs bound at the heterojunction.
Atomistic modelling showed that the IR photons promote bound charge pairs to
delocalised band states, similar to those formed just after singlet exciton
dissociation, which indicates that such states act as the gateway for charge
separation. Our results suggest that charge separation in efficient organic
photoconversion systems, occurs through hot-state charge delocalisation rather
than energy-gradient-driven intermolecular hopping.


title:
An introduction to lattice hadron spectroscopy for students without
  quantum field theoretical background

abstract:
  The intention of these lecture notes is to outline the basics of lattice
hadron spectroscopy to students from other fields of physics, e.g. from
experimental particle physics, who do not necessarily have a background in
quantum field theory. After a brief motivation and discussion of QCD, it is
explained, how QCD can in principle be solved numerically using lattice QCD.
The main part of these lecture notes is concerned with quantum numbers of
hadrons, corresponding hadron creation operators, and how the mass of a hadron
can be determined from a temporal correlation function of such operators.
Finally, three recent lattice hadron spectroscopy examples from the literature
are discussed on an elementary level.


title:
Simple CHT: A New Derivation of the Weakest Failure Detector for
  Consensus

abstract:
  The paper proposes an alternative proof that Omega, an oracle that outputs a
process identifier and guarantees that eventually the same correct process
identifier is output at all correct processes, provides minimal information
about failures for solving consensus in read-write shared-memory systems: every
oracle that gives enough failure information to solve consensus can be used to
implement Omega.
  Unlike the original proof by Chandra, Hadzilacos and Toueg (CHT), the proof
presented in this paper builds upon the very fact that 2-process wait-free
consensus is impossible. Also, since the oracle that is used to implement can
solve consensus, the implementation is allowed to directly access consensus
objects. As a result, the proposed proof is shorter and conceptually simpler
than the original one.


title: Proposal to Search for Heavy Neutral Leptons at the SPS

abstract:
  A new fixed-target experiment at the CERN SPS accelerator is proposed that
will use decays of charm mesons to search for Heavy Neutral Leptons (HNLs),
which are right-handed partners of the Standard Model neutrinos. The existence
of such particles is strongly motivated by theory, as they can simultaneously
explain the baryon asymmetry of the Universe, account for the pattern of
neutrino masses and oscillations and provide a Dark Matter candidate.
  Cosmological constraints on the properties of HNLs now indicate that the
majority of the interesting parameter space for such particles was beyond the
reach of the previous searches at the PS191, BEBC, CHARM, CCFR and NuTeV
experiments. For HNLs with mass below 2 GeV, the proposed experiment will
improve on the sensitivity of previous searches by four orders of magnitude and
will cover a major fraction of the parameter space favoured by theoretical
models.
  The experiment requires a 400 GeV proton beam from the SPS with a total of
2x10^20 protons on target, achievable within five years of data taking. The
proposed detector will reconstruct exclusive HNL decays and measure the HNL
mass. The apparatus is based on existing technologies and consists of a target,
a hadron absorber, a muon shield, a decay volume and two magnetic
spectrometers, each of which has a 0.5 Tm magnet, a calorimeter and a muon
detector. The detector has a total length of about 100 m with a 5 m diameter.
The complete experimental set-up could be accommodated in CERN's North Area.
  The discovery of a HNL would have a great impact on our understanding of
nature and open a new area for future research.


title:
Complexity Analysis in Presence of Control Operators and Higher-Order
  Functions (Long Version)

abstract:
  A polarized version of Girard, Scedrov and Scott's Bounded Linear Logic is
introduced and its normalization properties studied. Following Laurent, the
logic naturally gives rise to a type system for the lambda-mu-calculus, whose
derivations reveal bounds on the time complexity of the underlying term. This
is the first example of a type system for the lambda-mu-calculus guaranteeing
time complexity bounds for typable programs.


title:
Evolution of elliptic and triangular flow as a function of collision
  energy in a hybrid model

abstract:
  We study the collision energy dependence of elliptic flow v_2 and triangular
flow v_3 in Au+Au collisions within the energy range sqrt(s_{NN}) = 5-200 GeV,
utilizing a transport + hydrodynamics hybrid model. The transport part is
described by the Ultrarelativistic Quantum Molecular Dynamics (UrQMD) approach,
combined with an intermediate (3+1)-dimensional ideal hydrodynamical evolution
phase using a chiral model equation of state. We find the decrease of v_2
produced by hydrodynamics at lower collision energies partially compensated by
the transport dynamics. This does not apply to v_3, which falls to 0 in
midcentral collisions at sqrt(s_{NN}) = 5 GeV. We conclude that the triangular
flow provides the clearer signal for the formation of low-viscous fluid in
heavy ion collisions.


title: Test vectors and central L-values for GL(2)

abstract:
  We determine local test vectors for Waldspurger functionals for GL(2), in the
case where both the representation of GL(2) and the character of the degree two
extension are ramified, with certain restrictions. We use this to obtain an
explicit version of Waldspurger's formula relating twisted central L-values of
automorphic representations on GL(2) with certain toric period integrals. As a
consequence, we generalize an average value formula of Feigon and Whitehouse,
and obtain some nonvanishing results.


title:
Adaptive Modulation in Multi-user Cognitive Radio Networks over Fading
  Channels

abstract:
  In this paper, the performance of adaptive modulation in multi-user cognitive
radio networks over fading channels is analyzed. Multi-user diversity is
considered for opportunistic user selection among multiple secondary users. The
analysis is obtained for Nakagami-$m$ fading channels. Both adaptive continuous
rate and adaptive discrete rate schemes are analysed in opportunistic spectrum
access and spectrum sharing. Numerical results are obtained and depicted to
quantify the effects of multi-user fading environments on adaptive modulation
operating in cognitive radio networks.


title:
The reachability problem for vector addition systems with a stack is not
  elementary

abstract:
  By adapting the iterative yardstick construction of Stockmeyer, we show that
the reachability problem for vector addition systems with a stack does not have
elementary complexity. As a corollary, the same lower bound holds for the
satisfiability problem for a two-variable first-order logic on trees in which
unbounded data may label only leaf nodes. Whether the two problems are
decidable remains an open question.


title: Efficient Amplification of Photonic Qubits by Optimal Quantum Cloning

abstract:
  We demonstrate that a phase-independent quantum amplifier of a polarization
qubit is a complementary amplifier of the heralded qubit amplifier [N. Gisin,
S. Pironio and N. Sangouard, Phys. Rev. Lett. 105, 070501 (2010)]. It employs
the multi-functional cloner in 1 to 2 copying regime, capable of providing
approximate copies of qubits given by various probability distributions, and is
optimized for distributions with axial symmetry. Direct applications of the
proposed solution are possible in quantum technologies, doubling the range
where quantum information is coherently broadcast. It also outperforms natural
nonlinear amplifiers that use stimulated emission in bulk nonlinear materials.
We consider the amplifier to be an important tool for amplifying quantum
information sent via quantum channels with phase-independent damping.


title:
A Splitting Augmented Lagrangian Method for Low Multilinear-Rank Tensor
  Recovery

abstract:
  This paper studies a recovery task of finding a low multilinear-rank tensor
that fulfills some linear constraints in the general settings, which has many
applications in computer vision and graphics. This problem is named as the low
multilinear-rank tensor recovery problem. The variable splitting technique and
convex relaxation technique are used to transform this problem into a tractable
constrained optimization problem. Considering the favorable structure of the
problem, we develop a splitting augmented Lagrangian method to solve the
resulting problem. The proposed algorithm is easily implemented and its
convergence can be proved under some conditions. Some preliminary numerical
results on randomly generated and real completion problems show that the
proposed algorithm is very effective and robust for tackling the low
multilinear-rank tensor completion problem.


title:
Transition from a relativistic constituent-quark model to the
  quantum-chromodynamical asymptotics: a quantitative description of the pion
  electromagnetic form factor at intermediate values of the momentum transfer

abstract:
  We adopt a non-perturbative relativistic constituent-quark model for the
pi-meson electromagnetic form factor, which have successfully predicted
experimental results, and supplement it with the effective momentum-dependent
quark mass to study quantitatively the transition to the perturbative QCD
asymptotics. The required asymptotical behaviour (including both the Q^{-2}
fall-off and the correct coefficient) settles down automatically when the quark
mass is switched off; however, the present experimental data on the form factor
suggest that this cannot happen at the values of the momentum transfer below
~10 GeV^2. The effective constituent-quark mass below this scale acquires
substantial non-perturbative contributions.


title: Potts model, parametric maxflow and k-submodular functions

abstract:
  The problem of minimizing the Potts energy function frequently occurs in
computer vision applications. One way to tackle this NP-hard problem was
proposed by Kovtun [19,20]. It identifies a part of an optimal solution by
running $k$ maxflow computations, where $k$ is the number of labels. The number
of "labeled" pixels can be significant in some applications, e.g. 50-93% in our
tests for stereo. We show how to reduce the runtime to $O(\log k)$ maxflow
computations (or one {\em parametric maxflow} computation). Furthermore, the
output of our algorithm allows to speed-up the subsequent alpha expansion for
the unlabeled part, or can be used as it is for time-critical applications.
  To derive our technique, we generalize the algorithm of Felzenszwalb et al.
[7] for {\em Tree Metrics}. We also show a connection to {\em $k$-submodular
functions} from combinatorial optimization, and discuss {\em $k$-submodular
relaxations} for general energy functions.


title: Rational points on some Fermat curves and surfaces over finite fields

abstract:
  We give an explicit description of the F_{q^i}-rational points on the Fermat
curve u^{q-1}+v^{q-1}+w^{q-1}=0 for each i=1,2,3. As a consequence, we observe
that for any such point (u,v,w), the product uvw is a cube in F_{q^i}. We also
describe the F_{q^2}-rational points on the Fermat surface
u^{q-1}+v^{q-1}+w^{q-1}+x^{q-1}=0, and show that the product of the coordinates
of any such points is a square.


title: Deformation of algebraic cycle classes in characteristic zero

abstract:
  We study a formal deformation problem for rational algebraic cycle classes
motivated by Grothendieck's variational Hodge conjecture. We argue that there
is a close connection between the existence of a Chow-K\"unneth decomposition
and the existence of expected deformations of cycles. This observation applies
in particular to abelian schemes.


title: Axions as Hot and Cold Dark Matter

abstract:
  The presence of a hot dark matter component has been hinted at 3 sigma by a
combination of the results from different cosmological observations. We examine
a possibility that pseudo Nambu-Goldstone bosons account for both hot and cold
dark matter components. We show that the QCD axions can do the job for the
axion decay constant f_a < O(10^10) GeV, if they are produced by the saxion
decay and the domain wall annihilation. We also investigate the cases of
thermal QCD axions, pseudo Nambu-Goldstone bosons coupled to the standard model
sector through the Higgs portal, and axions produced by modulus decay.


title: Covers and Normal Covers of Finite Groups

abstract:
  For a finite non cyclic group $G$, let $\gamma(G)$ be the smallest integer
$k$ such that $G$ contains $k$ proper subgroups $H_1,\dots,H_k$ with the
property that every element of $G$ is contained in $H_i^g$ for some $i \in
\{1,\dots,k\}$ and $g \in G.$ We prove that if $G$ is a noncyclic permutation
group of degree $n,$ then $\gamma(G)\leq (n+2)/2.$ We then investigate the
structure of the groups $G$ with $\gamma(G)=\sigma(G)$ (where $\sigma(G)$ is
the size of a minimal cover of $G$) and of those with $\gamma(G)=2.$


title: Low-frequency oscillations in narrow vibrated granular systems

abstract:
  We present simulations and a theoretical treatment of vertically vibrated
granular media. The systems considered are confined in narrow
quasi-two-dimensional and quasi-one-dimensional (column) geometries, where the
vertical extension of the container is much larger than both horizontal
lengths. The additional geometric constraint present in the column setup
frustrates the convection state that is normally observed in wider geometries.
This makes it possible to study collective oscillations of the grains with a
characteristic frequency that is much lower than the frequency of energy
injection. The frequency and amplitude of these oscillations are studied as a
function of the energy input parameters and the size of the container. We
observe that, in the quasi-two-dimensional setup, low-frequency oscillations
are present even in the convective regime. This suggests that they may play a
significant role in the transition from a density inverted state to convection.
Two models are also presented; the first one, based on Cauchy's equations, is
able to predict with high accuracy the frequency of the particles' collective
motion. This first principles model requires a single input parameter, i.e, the
centre of mass of the system. The model shows that a sufficient condition for
the existence of the low-frequency mode is an inverted density profile with
distinct low and high density regions, a condition that may apply to other
systems too. The second, simpler model just assumes an harmonic oscillator like
behaviour and, using thermodynamic arguments, is also able to reproduce the
observed frequencies with high accuracy.


title: VCG Auction Mechanism Cost Expectations and Variances

abstract:
  We consider Vickrey-Clarke-Groves (VCG) auctions for a very general
combinatorial structure, in an average-case setting where item costs are
independent, identically distributed uniform random variables. We prove that
the expected VCG cost is at least double the expected nominal cost, and exactly
double when the desired structure is a basis of a bridgeless matroid. In the
matroid case we further show that, conditioned upon the VCG cost, the
expectation of the nominal cost is exactly half the VCG cost, and we show
several results on variances and covariances among the nominal cost, the VCG
cost, and related quantities. As an application, we find the asymptotic
variance of the VCG cost of the minimum spanning tree in a complete graph with
random edge costs.


title: Time Evolution in the external field problem of Quantum Electrodynamics

abstract:
  A general problem of quantum field theories is the fact that the free vacuum
and the vacuum for an interacting theory belong to different, non-equivalent
representations of the canonical (anti-)commutation relations. In the external
field problem of QED, we encounter this problem in the form that the Dirac time
evolution for an external field with non-vanishing magnetic components will not
satisfy the Shale-Stinespring condition, known to be necessary and sufficient
for the existence of an implementation on the fermionic Fock space. Therefore,
a second quantization of the time evolution in the usual way is impossible. In
this thesis, we present several rigorous approaches to QED with time-dependent,
external fields and analyze in what sense a time evolution can exist in the
second quantized theory. We study different constructions of the fermionic Fock
space and prove their equivalence. We study and compare the results of Deckert
et. al. (2010), where the time evolution is realized as unitary transformations
between time-varying Fock spaces, with those of Langmann and Mickelsson (1996),
who construct a "renormalization" for the time evolution and present a method
to fix the phase of the second quantized scattering operator by parallel
transport in a principle fibre bundle over the restricted, general linear group
acting on the fermionic Fock space. We provide rigorous proof for the fact that
the second quantization by parallel transport preserves causality. These
findings seem to refute claims made in Scharf (1995) that the phase of the
second quantized S-matrix is essentially determined by the requirement of
causality. We propose a simple solution to the problem of gauge anomalies in
the procedure of Langmann and Mickelsson, showing that the second quantization
of the scattering operator can be made gauge-invariant by using a suitable
class of renormalizations.


title:
Infrared timing with SPICA: Probing the formation of stellar-mass
  compact object jets in real-time

abstract:
  The time domain remains, in many respects, the least explored of parameter
spaces in astronomical studies. The purpose of this article is to encourage the
SPICA community to consider the potential of rapid infrared timing
observations. The specific example considered is that of variable emission from
relativistic jets in compact accreting objects, whose formation and powering
mechanisms we still do not understand. Infrared observations have the potential
to give us fundamental insight on the conditions required for jet formation in
accreting stellar-mass black holes and neutron stars. This is because particle
acceleration is thought to be magnetically-driven, and the spectral transition
between optically-thin and self-absorbed jet synchrotron radiation lies in the
infrared. We review recent observations from WISE showing that we have the
capability to measure key physical parameters of the jet, and their
time-dependence on rapidly-changing conditions in the accretion flow around the
black hole (on timescales of just a few seconds). SPICA will provide a
breakthrough in this field because of its sensitivity and broadband coverage,
and we detail an example SPICA observation on short (tens of milliseconds)
timescales. We believe that SPICA has the potential to make great impact on
time domain science, and we discuss some technical requirements that will
enable this.


title:
Local digital estimators of intrinsic volumes for Boolean models and in
  the design based setting

abstract:
  In order to estimate the specific intrinsic volumes of a planar Boolean model
from a binary image, we consider local digital algorithms based on weighted
sums of $2\times 2$ configuration counts. For Boolean models with balls as
grains, explicit formulas for the bias of such algorithms are derived,
resulting in a set of linear equations that the weights must satisfy in order
to minimize the bias in high resolution. These results generalize to larger
classes of random sets, as well as to the design based situation, where a fixed
set is observed on a stationary isotropic lattice. Finally, the formulas for
the bias obtained for Boolean models are applied to existing algorithms in
order to compare their accuracy.


title: A four-component Camassa-Holm type hierarchy

abstract:
  We consider a 3$\times$3 spectral problem which generates four-component CH
type systems. The bi-Hamiltonian structure and infinitely many conserved
quantities are constructed for the associated hierarchy. Some possible
reductions are also studied.


title: Ferrimagnetic Slater Insulator Phase of the Sn/Ge(111) Surface

abstract:
  We have performed the semilocal and hybrid density-functional theory (DFT)
studies of the Sn/Ge(111) surface to identify the origin of the observed
insulating ${\sqrt{3}}{\times}{\sqrt{3}}$ phase below ${\sim}$30 K. Contrasting
with the semilocal DFT calculation predicting a metallic 3${\times}$3 ground
state, the hybrid DFT calculation including van der Waals interactions shows
that the insulating ferrimagnetic structure with ${\sqrt{3}}{\times}{\sqrt{3}}$
structural symmetry is energetically favored over the metallic 3${\times}$3
structure. It is revealed that the correction of self-interaction error with a
hybrid exchange-correlation functional gives rise to a band-gap opening induced
by a ferrimagnetic order. The results manifest that the observed insulating
phase is attributed to the Slater mechanism via itinerant magnetic order rather
than the hitherto accepted Mott-Hubbard mechanism via electron correlations.


title: On multigrid convergence of local algorithms for intrinsic volumes

abstract:
  Local digital algorithms based on $n\times \dots \times n$ configuration
counts are commonly used within science for estimating intrinsic volumes from
binary images. This paper investigates multigrid convergence of such
algorithms. It is shown that local algorithms for intrinsic volumes other than
volume are not multigrid convergent on the class of convex polytopes. In fact,
counter examples are plenty. On the other hand, for convex particles in 2D with
a lower bound on the interior angles, a multigrid convergent local algorithm
for the Euler characteristic is constructed. Also on the class of $r$-regular
sets, counter examples to multigrid convergence are constructed for the surface
area and the integrated mean curvature.


title: Non-Markovian effect on remote state preparation

abstract:
  Memory effect of non-Markovian dynamics in open quantum systems is often
believed to be beneficial for quantum information processing. In this work, we
employ an experimentally controllable two-photon open system, with one photon
experiencing a dephasing environment and the other being free from noise, to
show that non-Markovian effect may also have a negative impact on quantum tasks
such as remote state preparation: For a certain period of controlled time
interval, stronger non-Markovian effect yields lower fidelity of remote state
preparation, as opposed to the common wisdom that more information leads to
better performance. As a comparison, a positive non-Markovian effect on the RSP
fidelity with another typical non-Markovian noise is analyzed. Consequently,
the observed dual character of non-Markovian effect will be of great importance
in the field of open systems engineering.


title:
Liquid Metal Flow Can Be One Clue to Explain the Frequently Observed
  Fluid-Like Matters on Mars

abstract:
  The frequently discovered flooding structure on Mars and other planets has
long been an intriguing mystery remained un-disclosed so far. Considering that
on Earth, quite a few low melting point liquid metals or their alloy can be
candidates of fluid like matters, we proposed here that there might also exists
certain liquid metal instead of water or methane alone on Mars or the like
planets. Compared with water, such liquid metal would be much easier to stay at
the Mars surface because of its low melting point however extremely high
evaporation point. Along this theoretical route, quite a few observations on
the fluid like matters in former space explorations can be well interpreted.
Such hypothesis for the existence of liquid metal on Mars surface does not mean
refuting the possibility of water on Mars. This new point would be helpful for
planning further exploration of Mars in a sense according to the characters of
liquid metal. It at least identifies one more target fluid towards either
finding or denying life at outer space. Whether the planet could harbor life in
some form or it reaffirms Mars as an important future destination for human
exploration still needs serious but not just enthusiasm explorations.


title:
Inflation, unemployment, and labour force. Phillips curves and long-term
  projections for Austria

abstract:
  We model the rate of inflation and unemployment in Austria since the early
1960s within the Phillips/Fisher framework. The change in labour force is the
driving force representing economic activity in the Phillips curve. For
Austria, this macroeconomic variable was first tested as a predictor of
inflation and unemployment in 2005 with the involved time series ended in 2003.
Here we extend all series by nine new readings available since 2003 and
re-estimate the previously estimated relationships between inflation,
unemployment, and labour force. As before, a structural break is allowed in
these relationships, which is related to numerous changes in definitions in the
1980s. The break year is estimated together with other model parameters by the
Boundary Element Method with the LSQ fitting between observed and predicted
integral curves. The precision of inflation prediction, as described by the
root-mean-square (forecasting) error is by 20% to 70% better than that
estimated by AR(1) model. The estimates of model forecasting error are
available for those time series where the change in labour force leads by one
(the GDP deflator) or two (CPI) years. For the whole period between 1965 and
2012 as well as for the intervals before and after the structural break (1986
for all inflation models) separately, our model is superior to the na\"ive
forecasting, which in turn, is not worse than any other forecasting model. The
level of statistical reliability and the predictive power of the link between
inflation and labour force imply that the National Bank of Austria does not
control inflation and unemployment beyond revisions to definitions. The labour
force projection provided by Statistic Austria allows foreseeing inflation at a
forty-year horizon: the rate of CPI inflation will hover around 1.3% and the
GDP deflator will likely sink below zero between 2018 and 2034.


title:
A study of the fractional quantum Hall effect: Odd and even denominator
  plateaux

abstract:
  We present a different approach to the fractional quantum Hall effect (FQHE),
focusing it as a consequence of the change in the symmetry of the Hamiltonian
of every electron in a two-dimensional electron gas (2DEG) under the
application of a magnetic field and in the presence of an electrostatic
potential due to the ionized impurities, and leading to a breaking of the
degeneration of the Landau levels. As the magnetic field increases the effect
of that electrostatic potential evolves, changing in turn the spatial symmetry
of the Hamiltonian: from continuous to discrete one. The aim of both works is
to give a different picture not only of the FQHE phenomenon, but a coherent one
with the integer quantum Hall effect (IQHE) and consistent with the model
already described in Hidalgo7, 8, 9. Therefore the model gives a global view of
both effects, showing that they are aspects of the same phenomenon, and
justifying not only the appearance of the odd denominator plateaux but also the
even ones; and giving some physical reasons for the experimental fact that
there are much more odd than even denominator plateaux, hardly observed


title: Einstein's Equivalence Principle and the Gravitational Red Shift II

abstract:
  Long before the general theory of relativity was finally formulated in 1916,
arguments based entirely on Einstein's equivalence principle predicted the well
known phenomenon of the gravitational red shift. Precisely the same arguments
are widely being used today to derive the same phenomenon. Accordingly, it is
often claimed that the observed gravitational red shift is a verification of
the equivalence principle rather than a verification of the full theory of
general relativity. Here we show that, contrary to these claims, the arguments
based on the equivalence principle are false and that \it{only the full theory
of general relativity can correctly and unambiguously predict the gravitational
red shift}.


title: On the $L^q$-spectrum of planar self-affine measures

abstract:
  We study the dimension theory of a class of planar self-affine multifractal
measures. These measures are the Bernoulli measures supported on box-like
self-affine sets, introduced by the author, which are the attractors of
iterated function systems consisting of contracting affine maps which take the
unit square to rectangles with sides parallel to the axes. This class contains
the self-affine measures recently considered by Feng and Wang as well as many
other measures. In particular, we allow the defining maps to have non-trivial
rotational and reflectional components. Assuming the rectangular open set
condition, we compute the $L^q$-spectrum by means of a $q$-modified singular
value function.
  A key application of our results is a \emph{closed form expression} for the
$L^q$-spectrum in the case where there are no mappings that switch the
coordinate axes. This is useful for computational purposes and also allows us
to prove differentiability of the $L^q$-spectrum at $q=1$ in the more difficult
`non-multiplicative' situation. This has applications concerning the Hausdorff,
packing and entropy dimension of the measure as well as the Hausdorff and
packing dimension of the support. Due to the possible inclusion of axis
reversing maps, we are led to extend some results of Peres and Solomyak on the
existence of $L^q$-spectrum of self-similar measures to the graph-directed
case.


title: Emergence of Cosmic Space and Minimal Length in Quantum Gravity

abstract:
  An emergence of cosmic space has been suggested by Padmanabhan in
[arXiv:1206.4916]. This new interesting approach argues that the expansion of
the universe is due to the difference between the number of degrees of freedom
on a holographic surface and the one in the emerged bulk. In this paper, we
derive, using emergence of cosmic space framework, the general dynamical
equation of FRW universe filled with a perfect fluid by considering a generic
form of the entropy as a function of area. Our derivation is considered as a
generalization of emergence of cosmic space with a general form of entropy. We
apply our equation with higher dimensional spacetime and derive modified
Friedmann equation in Gauss-Bonnet gravity. We then apply our derived equation
with the corrected entropy-area law that follows from Generalized Uncertainty
Principle (GUP) and derive a modified Friedmann equations due to the GUP. We
then derive the modified Raychaudhuri equation due to GUP in emergence of
cosmic space framework and investigate it using fixed point method. Studying
this modified Raychaudhuri equation leads to non-singular solutions which may
resolve singularities in FRW universe.


title:
Low-temperature magnetisation process in the cubic pyrochlore quantum
  antiferromagnet, Er2Ti2O7

abstract:
  We report low-temperature susceptibility and magnetisation data for the cubic
pyrochlore Er2Ti2O7. By performing the measurements on single crystals we are
able to establish the degree of magnetic anisotropy present in this compound
and to determine the critical values for magnetic field induced transitions
below the magnetic ordering temperature of 1.2 K. We also present a magnetic
H-T phase diagram of this quantum XY antiferromagnet for different directions
of an applied field.


title:
On hitting times for simple random walk on dense Erd\"os-R\'enyi random
  graphs

abstract:
  Let $G(N,p)=(V,E)$ be an Erd\"os-R\'enyi random graph and $(X_n)_{n \in
\mathbb{N}}$ be a simple random walk on it. We study the the order of magnitude
of $\sum_{i \in V} \pi_ih_{ij} $ where $\pi_i=d_i / 2|E|$ for $d_i$ the number
of neighbors of node $i$ and $h_{ij}$ the hitting time for $(X_n)_{n \in
\mathbb{N}}$ between nodes $i$ and $j$, in a regime of $p=p(N)$ such that
$G(N,p)$ is almost surely connected as $N\to\infty$. Our main result is that
$\sum_{i \in V} \pi_ih_{ij} $ is almost surely of order $N(1+o(1))$ as $N\to
\infty$, which coincides with previous results in the physics literature
\cite{sood}, though our techniques are based on large deviations bounds on the
number of neighbors of a typical node and the number of edges in $G(N,p)$
together with recent work on bounds on the spectrum of the (random) adjacency
matrix of $G(N,p)$.


title:
Unveiling the circumstellar environment towards a massive young stellar
  object

abstract:
  As a continuation of a previous work, in which we found strong evidence of
massive molecular outflows towards a massive star forming site, we present a
new study of this region based on very high angular resolution observations
with the aim of discovering the outflow driven mechanism. Using near-IR data
acquired with Gemini-NIRI at the broad H- and Ks-bands, we study a region of
22" x 22" around the UCHII region G045.47+0.05, a massive star forming site at
the distance of about 8 kpc. To image the source with the highest spatial
resolution possible we employed the adaptative optic system ALTAIR, achieving
an angular resolution of about 0.15". We discovered a cone-like shape nebula
with an opening angle of about 90 degree extending eastwards the IR source
2MASS J19142564+1109283, a very likely MYSO. This morphology suggests a cavity
that was cleared in the circumstellar material and its emission may arise from
scattered continuum light, warm dust, and likely emission lines from
shock-excited gas. The nebula, presenting arc-like features, is connected with
the IR source through a jet-like structure, which is aligned with the blue
shifted CO outflow found in a previous study. The near-IR structure lies ~3"
north of the radio continuum emission, revealing that it is not spatially
coincident with the UCHII region. The observed morphology and structure of the
near-IR nebula strongly suggest the presence of a precessing jet. In this study
we have resolved the circumstellar ambient (in scale of a thousand A.U.) of a
distant MYSO, indeed one of the farthest cases.


title: Attainment results for nematic elastomers

abstract:
  We consider a class of non-quasiconvex frame indifferent energy densities
which includes Ogden-type energy densities for nematic elastomers. For the
corresponding geometrically linear problem we provide an explicit minimizer of
the energy functional satisfying a nontrivial boundary condition. Other
attainment results, both for the nonlinear and the linearized model, are
obtained by using the theory of convex integration introduced by M\"uller and
Sver\'ak in the context of crystalline solids.


title: Weyl anomaly of conformal higher spins on six-sphere

abstract:
  This paper is a sequel to arXiv:1309.0785 were we computed the Weyl anomaly
a-coefficient on d-sphere for higher-derivative conformal higher spin field in
d=4 and shown that it matches the expression found in arXiv:1306.5242 by a
"holographic" method from a ratio of massless higher spin determinants in
AdS_5. Here we repeat the same computation on 6-sphere and demonstrate that the
result agrees again with the one following from AdS_7. We also discuss
explicitly similar matching in the d=2 case.


title: Anomalies of Dirac type operators on Euclidean space

abstract:
  We develop by example a type of index theory for non-Fredholm operators. A
general framework using cyclic homology for this notion of index was introduced
in a separate article [CaKa13] where it may be seen to generalise earlier ideas
of Carey-Pincus and Gesztesy-Simon on this problem. Motivated by an example in
two dimensions in [BGG+87] we introduce in this paper a class of examples of
Dirac type operators on R^{2n} that provide non-trivial examples of our
homological approach. Our examples may be seen as extending old ideas about the
notion of anomaly introduced by physicists to handle topological terms in
quantum action principles with an important difference, namely we are dealing
with purely geometric data that can be seen to arise from the continuous
spectrum of our Dirac type operators.


title: Quark Sector of the QCD Groundstate in Coulomb Gauge

abstract:
  The variational approach to Yang-Mills theory in Coulomb gauge is extended to
full QCD. For the quark sector we use a trial wave functional, which goes
beyond the previously used BCS-type state and which explicitly contains the
coupling of the quarks to transverse gluons. This quark wave functional
contains two variational kernels: One is related to the quark condensate and
occurs already in the BCS-type states. The other represents the form factor of
the coupling of the quarks to the transverse gluons. Minimization of the energy
density with respect to these kernels results in two coupled integral (gap)
equations. These equations are solved numerically using the confining part of
the non-Abelian color Coulomb potential and the lattice static gluon propagator
as input. With the additional coupling of quarks to transverse gluons included
the low energy chiral properties increase substantially towards their
phenomenological values. We obtain a reasonable description of the chiral
condensate, which for a vanishing current quark mass is obtained in the range
of 190-235 MeV. The coupling of the quarks to the transverse gluons enhances
the constituent quark mass by about 60% in comparison to the pure BCS ansatz.


title:
Long Range Ballistic Motion and Coherent Flow of Long Lifetime
  Polaritons

abstract:
  Exciton-polaritons can be created in semiconductor microcavities. These
quasiparticles act as weakly interacting bosons with very light mass, of the
order of $10^{-4}$ times the vacuum electron mass. Many experiments have shown
effects which can be viewed as due to a Bose-Einstein condensate, or
quasicondensate, of these particles. The lifetime of the particles in most of
those experiments has been of the order of a few picoseconds, leading to
significant nonequilibrium effects. By increasing the cavity quality, we have
made new samples with longer polariton lifetimes. With a photon lifetime on the
order of 100-200 ps, polaritons in these new structures can not only come
closer to reaching true thermal equilibrium, a desired feature for many
researchers working in this field, but they can also travel much longer
distances. We observe the polaritons to ballistically travel on the order of
one millimeter, and at higher densities we see transport of a coherent
condensate, or quasicondensate, over comparable distances. In this paper we
report a quantitative analysis of the flow of the polaritons both in a
low-density, classical regime, and in the coherent regime at higher density.
Our analysis gives us a measure of the intrinsic lifetime for photon decay from
the microcavity and a measure of the strength of interactions of the
polaritons.


title:
Linear Precoding Based on Polynomial Expansion: Large-Scale Multi-Cell
  MIMO Systems

abstract:
  Large-scale MIMO systems can yield a substantial improvement in spectral
efficiency for future communication systems. Due to the finer spatial
resolution achieved by a huge number of antennas at the base stations, these
systems have shown to be robust to inter-user interference and the use of
linear precoding is asymptotically optimal. However, most precoding schemes
exhibit high computational complexity as the system dimensions increase. For
example, the near-optimal RZF requires the inversion of a large matrix. This
motivated our companion paper, where we proposed to solve the issue in
single-cell multi-user systems by approximating the matrix inverse by a
truncated polynomial expansion (TPE), where the polynomial coefficients are
optimized to maximize the system performance. We have shown that the proposed
TPE precoding with a small number of coefficients reaches almost the
performance of RZF but never exceeds it. In a realistic multi-cell scenario
involving large-scale multi-user MIMO systems, the optimization of RZF
precoding has thus far not been feasible. This is mainly attributed to the high
complexity of the scenario and the non-linear impact of the necessary
regularizing parameters. On the other hand, the scalar weights in TPE precoding
give hope for possible throughput optimization. Following the same methodology
as in the companion paper, we exploit random matrix theory to derive a
deterministic expression for the asymptotic SINR for each user. We also provide
an optimization algorithm to approximate the weights that maximize the
network-wide weighted max-min fairness. The optimization weights can be used to
mimic the user throughput distribution of RZF precoding. Using simulations, we
compare the network throughput of the TPE precoding with that of the suboptimal
RZF scheme and show that our scheme can achieve higher throughput using a TPE
order of only 3.


title:
Generalized Negative Binomial Processes and the Representation of
  Cluster Structures

abstract:
  The paper introduces the concept of a cluster structure to define a joint
distribution of the sample size and its exchangeable random partitions. The
cluster structure allows the probability distribution of the random partitions
of a subset of the sample to be dependent on the sample size, a feature not
presented in a partition structure. A generalized negative binomial process
count-mixture model is proposed to generate a cluster structure, where in the
prior the number of clusters is finite and Poisson distributed and the cluster
sizes follow a truncated negative binomial distribution. The number and sizes
of clusters can be controlled to exhibit distinct asymptotic behaviors. Unique
model properties are illustrated with example clustering results using a
generalized Polya urn sampling scheme. The paper provides new methods to
generate exchangeable random partitions and to control both the cluster-number
and cluster-size distributions.


title: On the electrodynamics of neural networks

abstract:
  We present a microscopic approach for the coupling of cortical activity, as
resulting from proper dipole currents of pyramidal neurons, to the
electromagnetic field in extracellular fluid in presence of diffusion and Ohmic
conduction. Starting from a full-fledged three-compartment model of a single
pyramidal neuron, including shunting and dendritic propagation, we derive an
observation model for dendritic dipole currents in extracellular space and
thereby for the dendritic field potential that contributes to the local field
potential of a neural population. Under reasonable simplifications, we then
derive a leaky integrate-and-fire model for the dynamics of a neural network,
which facilitates comparison with existing neural network and observation
models. In particular, we compare our results with a related model by means of
numerical simulations. Performing a continuum limit, neural activity becomes
represented by a neural field equation, while an observation model for electric
field potentials is obtained from the interaction of cortical dipole currents
with charge density in non-resistive extracellular space as described by the
Nernst-Planck equation. Our work consistently satisfies the widespread dipole
assumption discussed in the neuroscientific literature.


title:
Inflationary susceptibilities, duality and large-scale magnetic fields
  generation

abstract:
  We investigate what can be said about the interaction of scalar fields with
Abelian gauge fields during a quasi-de Sitter phase of expansion and under the
assumption that the electric and the magnetic susceptibilities do not coincide.
The duality symmetry, transforming the magnetic susceptibility into the inverse
of the electric susceptibility, exchanges the magnetic and electric power
spectra. The mismatch between the two susceptibilities determines an effective
refractive index affecting the evolution of the canonical fields. The
constraints imposed by the duration of the inflationary phase and by the
magnetogenesis requirements pin down the rate of variation of the
susceptibilities that is consistent with the observations of the magnetic field
strength over astrophysical and cosmological scales but avoids back-reaction
problems. The parameter space of this magnetogenesis scenario is wider than in
the case when the susceptibilities are equal, as it happens when the inflaton
or some other spectator field is solely coupled to the standard gauge kinetic
term.


title:
A Fast Hadamard Transform for Signals with Sub-linear Sparsity in the
  Transform Domain

abstract:
  A new iterative low complexity algorithm has been presented for computing the
Walsh-Hadamard transform (WHT) of an $N$ dimensional signal with a $K$-sparse
WHT, where $N$ is a power of two and $K = O(N^\alpha)$, scales sub-linearly in
$N$ for some $0 < \alpha < 1$. Assuming a random support model for the non-zero
transform domain components, the algorithm reconstructs the WHT of the signal
with a sample complexity $O(K \log_2(\frac{N}{K}))$, a computational complexity
$O(K\log_2(K)\log_2(\frac{N}{K}))$ and with a very high probability
asymptotically tending to 1.
  The approach is based on the subsampling (aliasing) property of the WHT,
where by a carefully designed subsampling of the time domain signal, one can
induce a suitable aliasing pattern in the transform domain. By treating the
aliasing patterns as parity-check constraints and borrowing ideas from erasure
correcting sparse-graph codes, the recovery of the non-zero spectral values has
been formulated as a belief propagation (BP) algorithm (peeling decoding) over
a sparse-graph code for the binary erasure channel (BEC). Tools from coding
theory are used to analyze the asymptotic performance of the algorithm in the
very sparse ($\alpha\in(0,\frac{1}{3}]$) and the less sparse
($\alpha\in(\frac{1}{3},1)$) regime.


title: Discontinuous maps whose iterations are continuous

abstract:
  Let $X$ be a topological space and $f:X\to X$ a bijection. Let ${\mathcal
C}(X,f)$ be a set of integers such that an integer $n$ is an element of
${\mathcal C}(X,f)$ if and only if the bijection $f^n:X\to X$ is continuous. A
subset $S$ of the set of integers ${\mathbb Z}$ is said to be realizable if
there is a topological space $X$ and a bijection $f:X\to X$ such that
$S={\mathcal C}(X,f)$. A subset $S$ of ${\mathbb Z}$ containing 0 is called a
submonoid of ${\mathbb Z}$ if the sum of any two elements of $S$ is also an
element of $S$. We show that a subset $S$ of ${\mathbb Z}$ is realizable if and
only if $S$ is a submonoid of ${\mathbb Z}$. Then we generalize this result to
any submonoid in any group.


title: Combinatoire alg\'ebrique li\'ee aux ordres sur les permutations

abstract:
  This thesis comes within the scope of algebraic combinatorics and studies
problems related to three orders on permutations: the two said weak orders
(right and left) and the strong order or Bruhat order. The first part deals
with bases of multivariate polynomials. Most specifically, we study a product
of Grothendieck polynomials and prove that it can interpreted as a sum over the
Bruhat order. We also present our implementation of Grothendieck polynomials
and other bases in Sage. In a second part, we study the Tamari order binary
trees. We obtain a new enumeration formula on the Tamari lattice and a new
combinatorial prove of Chapoton's functional equation of the generating
functions of Tamari intervals. We extend our results to the m-Tamari case and
thus retrieve a formula given by Bousquet-M\'elou, Pr\'eville-Ratelle and Fusy.


title:
Linear Precoding Based on Polynomial Expansion: Reducing Complexity in
  Massive MIMO

abstract:
  Large-scale multi-user multiple-input multiple-output (MIMO) techniques have
the potential to bring tremendous improvements for future communication
systems. Counter-intuitively, the practical issues of having uncertain channel
knowledge, high propagation losses, and implementing optimal non-linear
precoding are solved more-or-less automatically by enlarging system dimensions.
However, the computational precoding complexity grows with the system
dimensions. For example, the close-to-optimal regularized zero-forcing (RZF)
precoding is very complicated to implement in practice, since it requires fast
inversions of large matrices in every coherence period. Motivated by the high
performance of RZF, we propose to replace the matrix inversion by a truncated
polynomial expansion (TPE), thereby obtaining the new TPE precoding scheme
which is more suitable for real-time hardware implementation. The degree of the
matrix polynomial can be adapted to the available hardware resources and
enables smooth transition between simple maximum ratio transmission (MRT) and
more advanced RZF.
  By deriving new random matrix results, we obtain a deterministic expression
for the asymptotic signal-to-interference-and-noise ratio (SINR) achieved by
TPE precoding in large-scale MIMO systems. Furthermore, we provide a
closed-form expression for the polynomial coefficients that maximizes this
SINR. To maintain a fixed per-user rate loss as compared to RZF, the polynomial
degree does not need to scale with the system, but it should be increased with
the quality of the channel knowledge and the signal-to-noise ratio (SNR).


title: Rotating charged black hole with Weyl corrections

abstract:
  We present firstly a four-dimensional spherical symmetric black hole with
small Weyl corrections and find that with increasing Weyl corrections the
region of the event horizon existence for the black hole in the parameter space
increases for the negative Weyl coupling parameter and decreases for the
positive one. Moreover, we also obtain a rotating charged black hole with weak
Weyl corrections by the method of complex coordinate transformation. Our
results show that the sign of Weyl coupling parameter $\alpha$ yields the
different spatial topology of the event horizons for the black hole with its
parameters lied in some special regions in the parameter space. We also analyze
the dependence of the ergosphere on the Weyl coupling parameter $\alpha$ and
find that with the increase of the Weyl corrections the ergosphere in the
equatorial plane becomes thick for a black hole with $\alpha>0$, but becomes
thin in the case with $\alpha<0$, which means that the energy extraction become
easier in the background of a black hole with the positive Weyl coupling
parameter, but more difficult in the background of a black hole with the
negative one.


title: Cauchy filters from Pelant's games

abstract:
  The language of finite games is used to rephrase Pelant's proof of his
result: The separable modification of the complete metric space
$C([0,\omega_1])$ is not complete.


title:
Dwarf spheroidal satellites of M31: I. Variable stars and stellar
  populations in Andromeda XIX

abstract:
  We present B,V time-series photometry of Andromeda XIX (And XIX), the most
extended (half-light radius of 6.2') of Andromeda's dwarf spheroidal
companions, that we observed with the Large Binocular Cameras at the Large
Binocular Telescope. We surveyed a 23'x 23' area centered on And XIX and
present the deepest color magnitude diagram (CMD) ever obtained for this
galaxy, reaching, at V~26.3 mag, about one magnitude below the horizontal
branch (HB). The CMD shows a prominent and slightly widened red giant branch,
along with a predominantly red HB, which, however, extends to the blue to
significantly populate the classical instability strip. We have identified 39
pulsating variable stars, of which 31 are of RR Lyrae type and 8 are Anomalous
Cepheids (ACs). Twelve of the RR Lyrae variables and 3 of the ACs are located
within And XIX's half light radius. The average period of the fundamental mode
RR Lyrae stars (<Pab> = 0.62 d, \sigma= 0.03 d) and the period-amplitude
diagram qualify And XIX as an Oosterhoff-Intermediate system. From the average
luminosity of the RR Lyrae stars (<V (RR)> = 25.34 mag, \sigma= 0.10 mag) we
determine a distance modulus of (m-M)$_0$=$24.52\pm0.23$ mag in a scale where
the distance to the Large Magellanic Cloud (LMC) is $18.5\pm0.1$ mag. The ACs
follow a well defined Period-Wesenheit (PW) relation that appears to be in very
good agreement with the PW relationship defined by the ACs in the LMC.


title: The Gale-Berlekamp game for complex Hadamard matrices

abstract:
  Associated to a complex Hadamard matrix $H\in M_N(\mathbb C)$ is the complex
probability measure $\mu\in\mathcal P(\mathbb C)$ describing the distribution
of $\varphi(a,b)=<a,Hb>$, where $a,b\in\mathbb T^N$ are random. This measure is
called "glow" of the matrix, due to the analogy with the Gale-Berlekamp
switching game, where $H,a,b$ are real. We prove here that: (1) $\mu$ becomes
complex Gaussian in the $N\to\infty$ limit, (2) the universality holds as well
at order 2, (3) the order 3 term seems to be quite interesting, particularly
for the master Hadamard matrices, (4) in the Fourier matrix case, some of the
higher order terms control counting problems for circulant Hadamard matrices.


title: End-to-End Text Recognition with Hybrid HMM Maxout Models

abstract:
  The problem of detecting and recognizing text in natural scenes has proved to
be more challenging than its counterpart in documents, with most of the
previous work focusing on a single part of the problem. In this work, we
propose new solutions to the character and word recognition problems and then
show how to combine these solutions in an end-to-end text-recognition system.
We do so by leveraging the recently introduced Maxout networks along with
hybrid HMM models that have proven useful for voice recognition. Using these
elements, we build a tunable and highly accurate recognition system that beats
state-of-the-art results on all the sub-problems for both the ICDAR 2003 and
SVT benchmark datasets.


title:
Role of magnetic chirality in polarization flip upon
  commensurate-incommensurate magnetic phase transition in YMn$_{2}$O$_{5}$

abstract:
  We have performed simultaneous measurements of magnetic chirality by using
polarized neutrons and electric polarization along the b-axis of single
crystals of YMn$^{4+}$(Mn$_{1-x}$Ga$_{x}$)$^{3+}$O$_{5}$ with $x=0.047$ and
0.12, in which nonmagnetic Ga-ions dilute Mn$^{3+}$ spins. The $x=0.047$ sample
exhibits high-temperature incommensurate (HT-ICM), commensurate (CM), and
low-temperature incommensurate (LT-ICM) magnetic phases in order of decreasing
temperature, whereas the $x=0.12$ sample exhibits only HT-ICM and LT-ICM
phases. Here, the CM and LT-ICM phases are ferroelectric and
weak-ferroelectric, respectively. Measurements conducted under zero field
heating after various field-cooling conditions evidence that the microscopic
mechanisms of the spin-driven ferroelectricity in the CM and LT-ICM phases are
different: the magnetic chirality of Mn$^{4+}$ cycloidal spins plays a dominant
role in the LT-ICM phase, whereas the magnetic exchange striction by the
Mn$^{4+}$-Mn$^{3+}$ chain plays a dominant role in the CM phase. The
polarization of YMn$_{2}$O$_{5}$ flips upon CM to LT-ICM phase transition
because the ferroelectricity driven by the magnetic chirality and the exchange
striction provides opposite directions of polarization.


title:
On the Normalized Spectral Representation of Max-Stable Processes on a
  Compact Set

abstract:
  The normalized spectral representation of a max-stable process on a compact
set is the unique representation where all spectral functions share the same
supremum. Among the class of equivalent spectral representations of a process,
the normalized spectral representation plays a distinctive role as a solution
of two optimization problems in the context of an efficient simulation of
max-stable processes. Our approach has the potential of considerably reducing
the simulation time of max-stable processes.


title: A Game-Theoretic Approach to Energy Trading in the Smart Grid

abstract:
  Electric storage units constitute a key element in the emerging smart grid
system. In this paper, the interactions and energy trading decisions of a
number of geographically distributed storage units are studied using a novel
framework based on game theory. In particular, a noncooperative game is
formulated between storage units, such as PHEVs, or an array of batteries that
are trading their stored energy. Here, each storage unit's owner can decide on
the maximum amount of energy to sell in a local market so as to maximize a
utility that reflects the tradeoff between the revenues from energy trading and
the accompanying costs. Then in this energy exchange market between the storage
units and the smart grid elements, the price at which energy is traded is
determined via an auction mechanism. The game is shown to admit at least one
Nash equilibrium and a novel proposed algorithm that is guaranteed to reach
such an equilibrium point is proposed. Simulation results show that the
proposed approach yields significant performance improvements, in terms of the
average utility per storage unit, reaching up to 130.2% compared to a
conventional greedy approach.


title: SMART - a computer program for modelling stellar atmospheres

abstract:
  Program SMART (Spectra and Model Atmospheres by Radiative Transfer) has been
composed for modelling atmospheres and spectra of hot stars (O, B and A
spectral classes) and studying different physical processes in them (Sapar &
Poolam\"ae 2003, Sapar et al. 2007). Line-blanketed models are computed
assuming plane-parallel, static and horizontally homogeneous atmosphere in
radiative, hydrostatic and local thermodynamic equilibrium. Main advantages of
SMART are its shortness, simplicity, user friendliness and flexibility for
study of different physical processes. SMART successfully runs on PC both under
Windows and Linux.


title: Electric control of spin in monolayer WSe2 field effect transistors

abstract:
  We report a first principles theoretical investigation of quantum transport
in monolayer WSe2 field effect transistor (FET). Due to a strong spin-orbit
interaction (SOI) and the atomic structure of the two-dimensional (2D) lattice,
monolayer WSe2 has an interesting electronic structure that exhibits
Zeeman-like up-down spin texture near the K and K' points of the Brillouin
zone. In a FET, the gate electric field induces an extra, externally tunable
SOI that re-orients the spins into a Rashba-like texture thereby realizing
electric control of the spin. Quantum transport is modulated by the spin
texture, namely by if the spin orientation of the carrier after the gated
channel region, matches or miss-matches that of the FET drain electrode. The
carrier current in the FET is labelled both the spin index and the valley
index, realizing spintronics and valleytronics in the same device.


title: Topological phases in small quantum Hall samples

abstract:
  Topological order has proven a useful concept to describe quantum phase
transitions which are not captured by the Ginzburg-Landau type of
symmetry-breaking order. However, lacking a local order parameter, topological
order is hard to detect. One way to detect is via direct observation of anyonic
properties of excitations which are usually discussed in the thermodynamic
limit, but so far has not been realized in macroscopic quantum Hall samples.
Here we consider a system of few interacting bosons subjected to the lowest
Landau level by a gauge potential, and theoretically investigate vortex
excitations in order to identify topological properties of different ground
states. Our investigation demonstrates that even in surprisingly small systems
anyonic properties are able to characterize the topological order. In addition,
focusing on a system in the Laughlin state, we study the robustness of its
anyonic behavior in the presence of tunable finite-range interactions acting as
a perturbation. A clear signal of a transition to a different state is
reflected by the system's anyonic properties.


title:
Tunable Landau-Zener transitions in a spin-orbit coupled Bose-Einstein
  condensate

abstract:
  The Landau-Zener (LZ) transition is one of the most fundamental phenomena in
quantum dynamics. It describes nonadiabatic transitions between quantum states
near an avoided crossing that can occur in diverse physical systems. Here we
report experimental measurements and tuning of LZ transitions between the
dressed eigenlevels of a Bose-Einstein condensate (BEC) that is synthetically
spin-orbit (SO) coupled. We measure the transition probability as the BEC is
accelerated through the SO avoided crossing and study its dependence on the
coupling between the diabatic (bare) states, eigenlevel slope, and eigenstate
velocity--the three parameters of the LZ model that are independently
controlled in our experiments. Furthermore, we performed time-resolved
measurements to demonstrate the breaking down of the spin-momentum locking of
the spin-orbit-coupled BEC in the nonadiabatic regime, and we determined the
diabatic switching time of the LZ transitions. Our observations show
quantitative agreement with the LZ model and numerical simulations of the
quantum dynamics in the quasimomentum space. The tunable LZ transition may be
exploited to enable a spin-dependent atomtronic transistor.


title:
Design and Testing of a Wireless Demonstrator for Large Instrumentation
  Systems

abstract:
  In this proceeding, we report the development of a wireless demonstrator
intended to readout instrumentation systems having thousands of channels. A
data acquisition system was designed and tested based on compliant
implementation of 802.11n based hardware and protocols. This project is for
large detectors containing photomultiplier tubes. Both free-space optical and
radio frequency techniques were tested for wireless power transfer. The
front-end circuitry, including a high-voltage power supply was powered
wirelessly, thus creating an all-wireless detector readout. The system was
successfully tested as a single detector module, which was powered wirelessly
and transmitted data wirelessly. The performance of the prototype system and
how a large scale implementation of the system might be realized are described
in this proceeding.


title: Loss in long-storage-time optical cavities

abstract:
  Long-storage-time Fabry-Perot cavities are a core component of many precision
measurement experiments. Optical loss in such cavities is a critical parameter
in determining their performance; however, it is very difficult to determine a
priori from independent characterisation of the individual cavity mirrors.
Here, we summarise three techniques for directly measuring this loss in situ
and apply them to a high-finesse, near-concentric, 2 m system. Through small
modifications of the cavity's length, we explore optical loss as a function of
beam spot size over the 1-3 mm range. In this regime we find that optical loss
is relatively constant at around 10 ppm per mirror and shows greater dependence
on the positions of the beam spots on the cavity optics than on their size.
These results have immediate consequences for the application of squeezed light
to advanced gravitational-wave interferometers.


title: Computing the Maslov index for large systems

abstract:
  We address the problem of computing the Maslov index for large linear
symplectic systems on the real line. The Maslov index measures the signed
intersections (with a given reference plane) of a path of Lagrangian planes.
The natural chart parameterization for the Grassmannian of Lagrangian planes is
the space of real symmetric matrices. Linear system evolution induces a Riccati
evolution in the chart. For large order systems this is a practical approach as
the computational complexity is quadratic in the order. The Riccati solutions,
however, also exhibit singularites (which are traversed by changing charts).
Our new results involve characterizing these Riccati singularities and two
trace formulae for the Maslov index as follows. First, we show that the number
of singular eigenvalues of the symmetric chart representation equals the
dimension of intersection with the reference plane. Second, the Cayley map is a
diffeomorphism from the space of real symmetric matrices to the manifold of
unitary symmetric matrices. We show the logarithm of the Cayley map equals the
arctan map (modulo 2i) and its trace measures the angle of the Langrangian
plane to the reference plane. Third, the Riccati flow under the Cayley map
induces a flow in the manifold of unitary symmetric matrices. Using the natural
unitary action on this manifold, we pullback the flow to the unitary Lie
algebra and monitor its trace. This avoids singularities, and is a natural
robust procedure. We demonstrate the effectiveness of these approaches by
applying them to a large eigenvalue problem. We also discuss the extension of
the Maslov index to the infinite dimensional case.


title:
Error Rate Analysis of Cognitive Radio Transmissions with Imperfect
  Channel Sensing

abstract:
  This paper studies the symbol error rate performance of cognitive radio
transmissions in the presence of imperfect sensing decisions. Two different
transmission schemes, namely sensing-based spectrum sharing (SSS) and
opportunistic spectrum access (OSA), are considered. In both schemes, secondary
users first perform channel sensing, albeit with possible errors. In SSS,
depending on the sensing decisions, they adapt the transmission power level and
coexist with primary users in the channel. On the other hand, in OSA, secondary
users are allowed to transmit only when the primary user activity is not
detected. Initially, for both transmission schemes, general formulations for
the optimal decision rule and error probabilities are provided for arbitrary
modulation schemes under the assumptions that the receiver is equipped with the
sensing decision and perfect knowledge of the channel fading, and the primary
user's received faded signals at the secondary receiver has a Gaussian mixture
distribution. Subsequently, the general approach is specialized to rectangular
quadrature amplitude modulation (QAM). More specifically, optimal decision rule
is characterized for rectangular QAM, and closed-form expressions for the
average symbol error probability attained with the optimal detector are derived
under both transmit power and interference constraints. The effects of
imperfect channel sensing decisions, interference from the primary user and its
Gaussian mixture model, and the transmit power and interference constraints on
the error rate performance of cognitive transmissions are analyzed.


title:
The High Time Resolution Universe Survey - IX: Polarimetry of
  long-period pulsars

abstract:
  We present a polarimetric analysis of 49 long-period pulsars discovered as
part of the High Time Resolution Universe (HTRU) southern survey. The sources
exhibit the typical characteristics of "old" pulsars, with low fractional
linear and circular polarisation and narrow, multicomponent profiles. Although
the position angle swings are generally complex, for two of the analysed
pulsars (J1622-3751 and J1710-2616) we obtained an indication of the geometry
via the rotating vector model. We were able to determine a value of the
rotation measure (RM) for 34 of the sources which, when combined with their
dispersion measures (DM), yields an integrated magnetic field strength along
the line of sight. With the data presented here, the total number of values of
RM associated to pulsars discovered during the HTRU southern survey sums to 51.
The RMs are not consistent with the hypothesis of a counter-clockwise direction
of the Galactic magnetic field within an annulus included between 4 and 6 kpc
from the Galactic centre. A partial agreement with a counter-clockwise sense of
the Galactic magnetic field within the spiral arms is however found in the area
of the Carina-Sagittarius arm.


title:
Monte Carlo evaluation of the equilibrium isotope effects using the
  Takahashi-Imada factorization of the Feynman path integral

abstract:
  The Feynman path integral approach for computing equilibrium isotope effects
and isotope fractionation corrects the approximations made in standard methods,
although at significantly increased computational cost. We describe an
accelerated path integral approach based on three ingredients: the fourth-
order Takahashi-Imada factorization of the path integral, thermodynamic
integration with respect to mass, and centroid virial estimators for relevant
free energy derivatives. While the frst ingredient speeds up convergence to the
quantum limit, the second and third improve statistical convergence. The
combined method is applied to compute the equilibrium constants for isotope
exchange reactions H2+D=H+HD and H2+D2=2HD.


title: Investigation of alpha-induced reactions on the p nucleus 168Yb

abstract:
  Cross sections for the 168Yb(alpha,gamma)172Hf and 168Yb(alpha,n)171$Hf
reactions were measured by means of the activation method using alpha particles
with energies between 12.9 MeV and 15.1 MeV. The spectroscopy of the gamma rays
emitted by the reaction products was performed using three different HPGe
detector types, namely clover-type high-purity germanium detectors, a
low-energy photon spectrometer detector, and a coaxial high-purity germanium
detector. The results were compared to Hauser-Feshbach statistical model
calculations. Within certain assumptions, astrophysical conclusions could be
drawn concerning the production of the p nucleus 168Yb. The data in this work
can serve as a contribution to the current very fragmentary experimental data
base for charged-particle induced reactions. In addition, the absolute
intensity for nine gamma-ray transitions following the electron capture decay
of 171Hf could be derived.