title:
The Atlas3D project -- XXXI. Nuclear radio emission in nearby early-type
  galaxies

abstract:
  We present the results of a high-resolution, 5 GHz, Karl G. Jansky Very Large
Array study of the nuclear radio emission in a representative subset of the
Atlas3D survey of early-type galaxies (ETGs). We find that 51 +/- 4% of the
ETGs in our sample contain nuclear radio emission with luminosities as low as
10^18 W/Hz. Most of the nuclear radio sources have compact (< 25-110 pc)
morphologies, although < 10% display multi-component core+jet or extended
jet/lobe structures. Based on the radio continuum properties, as well as
optical emission line diagnostics and the nuclear X-ray properties, we conclude
that the majority of the central 5 GHz sources detected in the Atlas3D galaxies
are associated with the presence of an active galactic nucleus (AGN). However,
even at sub-arcsecond spatial resolution, the nuclear radio emission in some
cases appears to arise from low-level nuclear star formation rather than an
AGN, particularly when molecular gas and a young central stellar population is
present. This is in contrast to popular assumptions in the literature that the
presence of a compact, unresolved, nuclear radio continuum source universally
signifies the presence of an AGN. Additionally, we examine the relationships
between the 5 GHz luminosity and various galaxy properties including the
molecular gas mass and - for the first time - the global kinematic state. We
discuss implications for the growth, triggering, and fueling of radio AGNs, as
well as AGN-driven feedback in the continued evolution of nearby ETGs.


title:
Pixel Color Magnitude Diagrams for Semi-Resolved Stellar Populations:
  The Star Formation History of Regions within the Disk and Bulge of M31

abstract:
  The analysis of stellar populations has, by and large, been developed for two
limiting cases: spatially-resolved stellar populations in the color-magnitude
diagram, and integrated light observations of distant systems. In between these
two extremes lies the semi-resolved regime, which encompasses a rich and
relatively unexplored realm of observational phenomena. Here we develop the
concept of pixel color magnitude diagrams (pCMDs) as a powerful technique for
analyzing stellar populations in the semi-resolved regime. pCMDs show the
distribution of imaging data in the plane of pixel luminosity vs. pixel color.
A key feature of pCMDs is that they are sensitive to all stars, including both
the evolved giants and the unevolved main sequence stars. An important variable
in this regime is the mean number of stars per pixel, $N_{\rm pix}$. Simulated
pCMDs demonstrate a strong sensitivity to the star formation history (SFH) and
allow one to break degeneracies between age, metallicity and dust based on two
filter data for values of $N_{\rm pix}$ up to at least $10^4$. We extract pCMDs
from Hubble Space Telescope (HST) optical imaging of M31 and derive
non-parametric SFHs from $10^6$ yr to $10^{10}$ yr for both the crowded disk
and bulge regions (where $N_{\rm pix}\approx30-10^3$). From analyzing a small
region of the disk we find a non-parametric SFH that is smooth and consistent
with an exponential decay timescale of 4 Gyr. The bulge SFH is also smooth and
consistent with a 2 Gyr decay timescale. pCMDs will likely play an important
role in maximizing the science returns from next generation ground and
space-based facilities.


title:
Precision tools and models to narrow in on the 750 GeV diphoton
  resonance

abstract:
  The hints for a new resonance at 750 GeV from ATLAS and CMS have triggered a
significant amount of attention. Since the simplest extensions of the standard
model cannot accommodate the observation, many alternatives have been
considered to explain the excess. Here we focus on several proposed
renormalisable weakly-coupled models and revisit results given in the
literature. We point out that physically important subtleties are often missed
or neglected. To facilitate the study of the excess we have created a
collection of 40 model files, selected from recent literature, for the
Mathematica package SARAH. With SARAH one can generate files to perform
numerical studies using the tailor-made spectrum generators FlexibleSUSY and
SPheno. These have been extended to automatically include crucial higher order
corrections to the diphoton and digluon decay rates for both CP-even and CP-odd
scalars. Additionally, we have extended the UFO and CalcHep interfaces of
SARAH, to pass the precise information about the effective vertices from the
spectrum generator to a Monte-Carlo tool. Finally, as an example to demonstrate
the power of the entire setup, we present a new supersymmetric model that
accommodates the diphoton excess, explicitly demonstrating how a large width
can be obtained. We explicitly show several steps in detail to elucidate the
use of these public tools in the precision study of this model.


title:
Rich Kozai-Lidov Dynamics in an Initially Thin and Eccentric Stellar
  Disc Around a Supermassive Black Hole

abstract:
  There is growing evidence of star formation in the vicinity of supermassive
black holes (SMBH) in galactic nuclei. A viable scenario for this process
assumes infall of a massive gas cloud towards the SMBH and subsequent formation
of a dense accretion disc which gives birth to the young stars. Numerical
hydrodynamical models indicate that this star formation process is rather fast
and it precedes full circularization of the accretion flow, i.e. the new stars
are born on elliptic orbits. By means of direct numerical N-body modeling, we
show in this paper that the non-zero eccentricity of the stellar discs around
the SMBH leads to an onset of various types of the Kozai-Lidov oscillations of
a non-negligible subset of individual orbits in the disc, showing a remarkable
robustness of this classical mechanism. Among others, we demonstrate that under
certain circumstances, presence of an additional spherical cluster (which is
generally known to damp Kozai-Lidov oscillations) may trigger such oscillations
due to affecting the internal flow of the angular momentum through the disc. We
conclude that the Kozai-Lidov oscillations are capable to substantially modify
the initial structure of the disc (its thickness and distribution of
eccentricities, in particular).


title:
Vacuum Stability and Radiative Electroweak Symmetry Breaking in an
  SO(10) Dark Matter Model

abstract:
  Vacuum stability in the Standard Model is problematic as the Higgs quartic
self-coupling runs negative at a renormalization scale of about $10^{10}$ GeV.
We consider a non-supersymmetric SO(10) grand unification model for which gauge
coupling unification is made possible through an intermediate scale gauge
group, $G_{\text{int}}=\text{SU}(3)_C\otimes \text{SU}(2)_L\otimes
\text{SU}(2)_R \otimes \text{U}(1)_{B-L}$. $G_{\text{int}}$ is broken by the
vacuum expectation value of a 126 of SO(10) which not only provides for
neutrino masses through the seesaw mechanism but also preserves a discrete
$\mathbb{Z}_2$ that can account for the stability of a dark matter candidate,
here taken to be the Standard Model singlet component of a bosonic 16. We show
that in addition to these features the model insures the positivity of the
Higgs quartic coupling through its interactions to the dark matter multiplet
and 126. We also show that the Higgs mass squared runs negative triggering
electroweak symmetry breaking. Thus, the vacuum stability is achieved along
with radiative electroweak symmetry breaking and captures two more important
elements of supersymmetric models without low-energy supersymmetry. The
conditions for perturbativity of quartic couplings and for radiative
electroweak symmetry breaking lead to tight upper and lower limits on the dark
matter mass, respectively, and this dark matter mass region (1.35-2 TeV) can be
probed in future direct detection experiments.


title:
Identifying Planetary Biosignature Impostors: Spectral Features of CO
  and O4 Resulting from Abiotic O2/O3 Production

abstract:
  O2 and O3 have been long considered the most robust individual biosignature
gases in a planetary atmosphere, yet multiple mechanisms that may produce them
in the absence of life have been described. However, these abiotic planetary
mechanisms modify the environment in potentially identifiable ways. Here we
briefly discuss two of the most detectable spectral discriminants for abiotic
O2/O3: CO and O4. We produce the first explicit self-consistent simulations of
these spectral discriminants as they may be seen by JWST. If JWST-NIRISS and/or
NIRSpec observe CO (2.35, 4.6 um) in conjunction with CO2 (1.6, 2.0, 4.3 um) in
the transmission spectrum of a terrestrial planet it could indicate robust CO2
photolysis and suggest that a future detection of O2 or O3 might not be
biogenic. Strong O4 bands seen in transmission at 1.06 and 1.27 um could be
diagnostic of a post-runaway O2-dominated atmosphere from massive H-escape. We
find that for these false positive scenarios, CO at 2.35 um, CO2 at 2.0 and 4.3
um, and O4 at 1.27 um are all stronger features in transmission than O2/O3 and
could be detected with SNRs $\gtrsim$ 3 for an Earth-size planet orbiting a
nearby M dwarf star with as few as 10 transits, assuming photon-limited noise.
O4 bands could also be sought in UV/VIS/NIR reflected light (at 0.345, 0.36,
0.38, 0.445, 0.475, 0.53, 0.57, 0.63, 1.06, and 1.27 um) by a next generation
direct-imaging telescope such as LUVOIR/HDST or HabEx and would indicate an
oxygen atmosphere too massive to be biologically produced.


title: Hourglass Fermions

abstract:
  Spatial symmetries in crystals are distinguished by whether they preserve the
spatial origin. We show how this basic geometric property gives rise to a new
topology in band insulators. We study spatial symmetries that translate the
origin by a fraction of the lattice period, and find that these nonsymmorphic
symmetries protect a novel surface fermion whose dispersion is shaped like an
hourglass; surface bands connect one hourglass to the next in an unbreakable
zigzag pattern. These exotic fermions are materialized in the large-gap
insulators: KHgX (X=As,Sb,Bi), which we propose as the first material class
whose topology relies on nonsymmorphic symmetries. Beside the hourglass
fermion, another surface of KHgX manifests a 3D generalization of the quantum
spin Hall effect, which has only been observed in 2D crystals. To describe the
bulk topology of nonsymmorphic crystals, we propose a non-Abelian
generalization of the geometric theory of polarization. Our nontrivial topology
originates from an inversion of the rotational quantum numbers, which we
propose as a fruitful criterion in the search for topological materials.


title:
Carbon Shell or Core Ignitions in White Dwarfs Accreting from Helium
  Stars

abstract:
  White dwarfs accreting from helium stars can stably burn at the accreted rate
and avoid the challenge of mass loss associated with unstable Helium burning
that is a concern for many Type Ia supernovae scenarios. We study binaries with
helium stars of mass $1.25 M_\odot\le M_{\rm{He}} \le 1.8 M_\odot$, which have
lost their hydrogen rich envelopes in an earlier common envelope event and now
orbit with periods ($P_{\rm orb}$) of several hours with non-rotating $0.84$
and $1.0 M_\odot$ C/O WDs. The helium stars fill their Roche lobes (RLs) after
exhaustion of central helium and donate helium on their thermal timescales
(${\sim}10^5$yr). As shown by others, these mass transfer rates coincide with
the steady helium burning range for WDs, and grow the WD core up to near the
Chandrasekhar mass ($M_{\rm Ch}$) and a core carbon ignition. We show here,
however, that many of these scenarios lead to an ignition of hot carbon ashes
near the outer edge of the WD and an inward going carbon flame that does not
cause an explosive outcome. For $P_{\rm orb} = 3$ hours, $1.0 M_\odot$ C/O WDs
with donor masses $M_{\rm He}\gtrsim1.8 M_\odot$ experience a shell carbon
ignition, while $M_{\rm He}\lesssim1.3 M_\odot$ will fall below the steady
helium burning range and undergo helium flashes before reaching core C
ignition. Those with $1.3 M_\odot \lesssim M_{\rm He} \lesssim 1.7 M_\odot$
will experience a core C ignition. We also calculate the retention fraction of
accreted helium when the accretion rate leads to recurrent weak helium flashes.


title:
Carbon and oxygen abundance gradients in NGC300 and M33 from optical
  recombination lines

abstract:
  We present deep spectrophotometry of several Hii regions in the nearby
low-mass spiral galaxies NGC 300 and M33. The data have been taken with UVES
and OSIRIS spectrographs attached to the 8m VLT and 10.4m GTC telescopes,
respectively. We have derived precise values of the physical conditions for
each object making use of several emission line-intensity ratios. In
particular, we have obtained direct determinations of the electron temperature
in all the observed objects. We detect pure recombination lines (RLs) of Cii
and Oii in several of the Hii regions, permitting to derive their C/H and C/O
ratios. We have derived the radial abundance gradient of O for each galaxy
making use of collisionally excited lines (CELs) and RLs, as well as the C and
N gradients using RLs and CELs, respectively. We obtain the first determination
of the C/H gradient of NGC 300 and improve its determination in the case of
M33. In both galaxies, the C/H gradients are steeper that those of O/H, leading
to negative C/O gradients. Comparing with similar results for other spiral
galaxies, we find a strong correlation between the slope of the C/H gradient
and M_V. We find that some Hii regions located close to the isophotal radius
(R_25) of NGC 300 and M33 show C/O ratios more similar to those typical of
dwarf galaxies than those of Hii regions in the discs of more massive spirals.
This may be related to the absence of flattening of the gradients in the
external parts of NGC 300 and M33. Finally, we find very similar N/H gradients
in both galaxies and a fair correlation between the slope of the N/H gradient
and M_V comparing with similar data for a sample of spiral galaxies.


title: LHC 750 GeV diphoton excess and muon $(g-2)$

abstract:
  We consider implications of the diphoton excess recently observed at the LHC
on the anomalous magnetic dipole moment of the muon $(g-2)_\mu = 2 a_\mu$,
hypothesizing that the possible 750 GeV resonance is a (pseudo)scalar particle.
The (pseudo)scalar-$\gamma$-$\gamma$ interaction implied by the diphoton events
might generically contribute to $a_\mu$ via 2-loop Barr-Zee type diagrams in a
broad class of models. If the scalar is an $SU(2)_L$ singlet, the new
contribution to $a_\mu$ is much smaller than the current anomaly, $\Delta a_\mu
\equiv a_\mu^{\rm exp}-a_\mu^{\rm SM} \approx (30 \pm 10) \times 10^{-10}$,
since the scalar can complete the Barr-Zee diagrams only through its mixing
with the Standard Model Higgs boson. If the (pseudo)scalar belongs to an
$SU(2)_L$ doublet in an extended Higgs sector, then by contrast, $\Delta a_\mu$
can be easily accommodated with the aid of an enhanced Yukawa coupling of the
(pseudo)scalar to the muon such as in the Type-II or -X two Higgs doublet
model.


title:
The rhythm of Fairall 9 -- I: Observing the spectral variability with
  XMM-Newton and NuSTAR

abstract:
  We present a multi-epoch X-ray spectral analysis of the Seyfert 1 galaxy
Fairall 9. Our analysis shows that Fairall 9 displays unique spectral
variability in that its ratio residuals to a simple absorbed power law in the
0.5-10 keV band remain constant with time in spite of large variations in flux.
This behavior implies an unchanging source geometry and the same emission
processes continuously at work at the timescale probed. With the constraints
from NuSTAR on the broad-band spectral shape, it is clear that the soft excess
in this source is a superposition of two different processes, one being blurred
ionized reflection in the innermost parts of the accretion disk, and the other
a continuum component such as spatially distinct Comptonizing region.
Alternatively, a more complex primary Comptonization component together with
blurred ionized reflection could be responsible.


title: WIMP Dark Matter in Composite Higgs Models and the Dilaton Portal

abstract:
  We study under which conditions a scalar particle is a viable WIMP Dark
Matter candidate with Higgs and dilaton interactions. The theory is a composite
Higgs model with top partial compositeness where both the Higgs and the Dark
Matter candidate arise as pseudo Goldstone boson of the coset SO(6)/SO(5) from
a new physics sector. We highlight the role of the dilaton in direct and
indirect searches. We find that a Dark Matter particle with a mass around
200-400 GeV and a relatively light dilaton are a fair prediction of the model.


title:
On a special property of tridiagonal matrices. Application to dual
  quasi-exactly solvable sextic potentials in quantum mechanics

abstract:
  We put forward and prove a simple theorem stating that the eigenvalues of a
tridiagonal matrix change their sign (as a set), once the signs of the diagonal
elements of the matrix are changed. We also provide an example of application
of this theorem in quantum physics. Specifically, we introduce the notion of
duality and self-duality for a sextic-polynomial quasi-exactly-solvable
potential, and demonstrate that the algebraic parts of the spectrum of the dual
potentials have signs opposite to one another (as sets). Our Theorem furnishes
an elegant one-line proof of this statement. In addition, we also prove it by
purely quantum-mechanical means - a far less straightforward method that
requires some effort.


title:
Mid-infrared interferometry of 23 AGN tori: On the significance of
  polar-elongated emission

abstract:
  Context. Detailed high resolution studies of AGN with mid-infrared (MIR)
interferometry have revealed parsec-sized dust emission elongated in the polar
direction in four sources.
  Aims. Using a larger, coherently analyzed sample of AGN observed with MIR
interferometry, we aim to identify elongated mid-infrared emission in a
statistical sample of sources. More specifically we wish to determine if there
is indeed a preferred direction of the elongation and whether this direction is
consistent with a torus-like structure or with a polar emission.
  Methods. We investigate the significance of the detection of an elongated
shape in the MIR emission by fitting elongated Gaussian models to the
interferometric data at 12 um. We pay special attention to 1) the uncertainties
caused by an inhomogeneous (u,v) coverage, 2) the typical errors in the
measurements and 3) the spatial resolution achieved for each object.
  Results. From our sample of 23 sources we are able to find elongated
parsec-scale MIR emission in five sources: three type 2s, one type 1i and one
type 1. Elongated emission in four of these sources has been published before;
NGC5506 is a new detection. The observed axis ratios are typically around 2 and
the position angle of the 12 um emission for all the elongated sources seems to
be always closer to the polar axis of the system than to the equatorial axis.
Two other objects, NGC4507 and MCG-5-23-16 with a reasonably well mapped (u,v)
coverage and good signal-to-noise ratios, appear to have a less elongated 12 um
emission.
  Conclusions. Our finding that sources showing elongated mid-infrared emission
are preferentially extended in polar direction sets strong constraints on torus
models or implies that both the torus and the NLR/outflow region have to be
modeled together. Especially also models used for SED fitting will have to be
revised to include emission from polar dust.


title:
On the universality of thermodynamics and $\eta/s$ ratio for the charged
  Lovelock black branes

abstract:
  We investigate general features of charged Lovelock black branes by giving a
detailed description of geometrical, thermodynamic and holographic properties
of charged Gauss-Bonnet (GB) black branes in five dimensions. We show that when
expressed in terms of effective physical parameters, the thermodynamic
behaviour of charged GB black branes is completely indistinguishable from that
of charged Einstein black branes. Moreover, the extremal, near-horizon limit of
the two classes of branes is exactly the same as they allow for the same
AdS$_2\times R_3$, near-horizon, exact solution. This implies that, although in
the UV the associated dual QFTs are different, they flow in the IR to the same
fixed point. The calculation of the shear viscosity to entropy ratio $\eta/s$
confirms these results. Despite the GB dual plasma has in general a
non-universal temperature-dependent $\eta/s$, it flows monotonically to the
universal value $1/4\pi$ in the IR. For negative (positive) GB coupling
constant, $\eta/s$ is an increasing (decreasing) function of the temperature
and the flow respects (violates) the KSS bound.


title:
On multidimensional solutions in the Einstein-Gauss-Bonnet model with a
  cosmological term

abstract:
  A D-dimensional gravitational model with Gauss-Bonnet and cosmological term
is considered. When ansatz with diagonal cosmological metrics is adopted, we
overview recent solutions for zero cosmological term and find new examples of
solutions for non-zero cosmological term and D = 8 with exponential dependence
of scale factors which describe an expansion of our 3-dimensional factor-space
and contraction of 4-dimensional internal space.


title:
Nuclear Magnetic Resonance studies of DNP-ready trehalose obtained by
  solid state mechanochemical amorphization

abstract:
  $^1$H nuclear spin-lattice relaxation and Dynamic Nuclear Polarization (DNP)
have been studied in amorphous samples of trehalose sugar doped with TEMPO
radicals by means of mechanical milling, in the 1.6 K $\div$ 4.2 K temperature
range. The radical concentration was varied between 0.34 and 0.81 $\%$. The
highest polarization of 15 \% at 1.6 K, observed in the sample with
concentration $0.50 \%$, is of the same order of magnitude of that reported in
standard frozen solutions with TEMPO. The temperature and concentration
dependence of the spin-lattice relaxation rate $1/T_{\text{1}}$, dominated by
the coupling with the electron spins, were found to follow power laws with an
exponent close to $3$ in all samples. The observed proportionality between
$1/T_{\text{1}}$ and the polarization rate $1/T_{\text{pol}}$, with a
coefficient related to the electron polarization, is consistent with the
presence of Thermal Mixing (TM) and a good contact between the nuclear and the
electron spins. At high electron concentration additional relaxation channels
causing a decrease in the nuclear polarization must be considered. These
results provide further support for a more extensive use of amorphous DNP-ready
samples, obtained by means of comilling, in dissolution DNP experiments and
possibly for $\textit{in vivo}$ metabolic imaging.


title:
Rural to urban population density scaling of crime and property
  transactions in English and Welsh Parliamentary Constituencies

abstract:
  Urban population scaling of resource use, creativity metrics, and human
behaviors has been widely studied. These studies have not looked in detail at
the full range of human environments which represent a continuum from the most
rural to heavily urban. We examined monthly police crime reports and property
transaction values across all 573 Parliamentary Constituencies in England and
Wales, finding that scaling models based on population density provided a far
superior framework to traditional population scaling. We found four types of
scaling: i) non-urban scaling in which a single power law explained the
relationship between the metrics and population density from the most rural to
heavily urban environments, ii) accelerated scaling in which high population
density was associated with an increase in the power-law exponent, iii)
inhibited scaling where the urban environment resulted in a reduction in the
power-law exponent but remained positive, and iv) collapsed scaling where
transition to the high density environment resulted in a negative scaling
exponent. Urban scaling transitions, when observed, took place universally
between 10 and 70 people per hectare. This study significantly refines our
understanding of urban scaling, making clear that some of what has been
previously ascribed to urban environments may simply be the high density
portion of non-urban scaling. It also makes clear that some metrics undergo
specific transitions in urban environments and these transitions can include
negative scaling exponents indicative of collapse. This study gives promise of
far more sophisticated scale adjusted metrics and indicates that studies of
urban scaling represent a high density subsection of overall scaling
relationships which continue into rural environments.


title:
Magnetic interactions at the nanoscale in trilayer titanates
  LaTiO$_3$/SrTiO$_3$/YTiO$_3$

abstract:
  We report on the phase diagram of competing magnetic interactions at
nanoscale in engineered ultra-thin trilayer heterostructures of
LaTiO$_{3}$/SrTiO$_{3}$/YTiO$_{3}$, in which the interfacial inversion symmetry
is explicitly broken. Combined atomic layer resolved scanning transmission
electron microscopy with electron energy loss spectroscopy and electrical
transport have confirmed the formation of a spatially separated two-dimensional
electron liquid and high density two-dimensional localized magnetic moments at
the LaTiO$_3$/SrTiO$_3$ and SrTiO$_3$/YTiO$_3$ interfaces, respectively.
Resonant soft X-ray linear dichroism spectroscopy has demonstrated the presence
of orbital polarization of the conductive LaTiO$_3$/SrTiO$_3$ and localized
SrTiO$_3$/YTiO$_3$ electrons. Our results provide a route with prospects for
exploring new magnetic interfaces, designing tunable two-dimensional
$d$-electron Kondo lattice, and potential spin Hall applications.


title:
Isoperimetry in supercritical bond percolation in dimensions three and
  higher

abstract:
  We study the isoperimetric subgraphs of the infinite cluster
$\textbf{C}_\infty$ for supercritical bond percolation on $\mathbb{Z}^d$ with
$d\geq 3$. Specifically, we consider the subgraphs of $\textbf{C}_\infty \cap
[-n,n]^d$ which have minimal open edge boundary to volume ratio. We prove a
shape theorem for these subgraphs, obtaining that when suitably rescaled, these
subgraphs converge almost surely to a translate of a deterministic shape. This
deterministic shape is itself an isoperimetric set for a norm we construct. As
a corollary, we obtain sharp asymptotics on a natural modification of the
Cheeger constant for $\textbf{C}_\infty \cap [-n,n]^d$. This settles a
conjecture of Benjamini for the version of the Cheeger constant defined here.


title: A Holographic Model for Quantum Critical Responses

abstract:
  We analyze the dynamical response functions of strongly interacting quantum
critical states described by conformal field theories (CFTs). We construct a
self-consistent holographic model that incorporates the relevant scalar
operator driving the quantum critical phase transition. Focusing on the finite
temperature dynamical conductivity $\sigma(\omega,T)$, we study its dependence
on our model parameters, notably the scaling dimension of the relevant
operator. It is found that the conductivity is well-approximated by a simple
ansatz proposed by Katz et al [1] for a wide range of parameters. We further
dissect the conductivity at large frequencies $\omega >> T$ using the operator
product expansion, and show how it reveals the spectrum of our model CFT. Our
results provide a physically-constrained framework to study the analytic
continuation of quantum Monte Carlo data, as we illustrate using the O(2)
Wilson-Fisher CFT. Finally, we comment on the variation of the conductivity as
we tune away from the quantum critical point, setting the stage for a
comprehensive analysis of the phase diagram near the transition.

categories: hep-th cond-mat.str-el cond-mat.supr-con gr-qc


title:
Emulating the one-dimensional Fermi-Hubbard model by a double chain of
  qubits

abstract:
  The Jordan-Wigner transformation maps a one-dimensional spin-1/2 system onto
a fermionic model without spin degree of freedom. A double chain of quantum
bits with XX and ZZ couplings of neighboring qubits along and between the
chains, respectively, can be mapped on a spin-full 1D Fermi-Hubbard model. The
qubit system can thus be used to emulate the quantum properties of this model.
We analyze physical implementations of such analog quantum simulators,
including one based on transmon qubits, where the ZZ interaction arises due to
an inductive coupling and the XX interaction due to a capacitive interaction.
We propose protocols to gain confidence in the results of the simulation
through measurements of local operators.


title:
Is the Hypothesis About a Low Entropy Initial State of the Universe
  Necessary for Explaining the Arrow of Time?

abstract:
  According to statistical mechanics, micro-states of an isolated physical
system (say, a gas in a box) at time $t_0$ in a given macro-state of
less-than-maximal entropy typically evolve in such a way that the entropy at
time $t$ increases with $|t-t_0|$ in both time directions. In order to account
for the observed entropy increase in only one time direction, the thermodynamic
arrow of time, one usually appeals to the hypothesis that the initial state of
the universe was one of very low entropy. In certain recent models of
cosmology, however, no hypothesis about the initial state of the universe is
invoked. We discuss how the emergence of a thermodynamic arrow of time in such
models can nevertheless be compatible with the above-mentioned consequence of
statistical mechanics, appearances to the contrary notwithstanding.


title: 2-permutations of lattice vertex operator algebras: Higher rank

abstract:
  The fusion rules of the 2-permutation orbifold of an arbitrary lattice vertex
operator algebra are determined by using the theory of quantum dimension.


title: Full two-photon downconversion of just a single photon

abstract:
  We demonstrate, both numerically and analytically, that it is possible to
generate two photons from one and only one photon. We characterize the output
two photon field and make our calculations close to reality by including
losses. Our proposal relies on real or artificial three-level atoms with a
cyclic transition strongly coupled to a one-dimensional waveguide. We show that
close to perfect downconversion with efficiency over 99% is reachable using
state-of-the-art Waveguide QED architectures such as photonic crystals or
superconducting circuits. In particular, we sketch an implementation in circuit
QED, where the three level atom is a transmon.


title:
Blow-up, steady states and long time behaviour of excitatory-inhibitory
  nonlinear neuron models

abstract:
  Excitatory and inhibitory nonlinear noisy leaky integrate and fire models are
often used to describe neural networks. Recently, new mathematical results have
provided a better understanding of them. It has been proved that a fully
excitatory network can blow-up in finite time, while a fully inhibitory network
has a global in time solution for any initial data. A general description of
the steady states of a purely excitatory or inhibitory network has been also
given. We extend this study to the system composed of an excitatory population
and an inhibitory one. We prove that this system can also blow-up in finite
time and analyse its steady states and long time behaviour. Besides, we
illustrate our analytical description with some numerical results. The main
tools used to reach our aims are: the control of an exponential moment for the
blow-up results, a more complicate strategy than that considered in C\'aceres,
Carrillo and Perthame (2011), for studying the number of steady states, entropy
methods combined with Poincar\'e inequalities for the long time behaviour and,
finally, high order numerical schemes together with parallel computation
techniques in order to obtain our numerical results.


title:
Solution of Conformable Fractional Ordinary Differential Equations via
  Differential Transform Method

abstract:
  Recently, a new fractional derivative called the conformable fractional
derivative is given which is based on the basic limit definition of the
derivative in [1]. Then, the fractional versions of chain rules, exponential
functions, Gronwall's inequality, integration by parts, Taylor power series
expansions is developed in [2]. In this paper, we give conformable fractional
differential transform method and its application to conformable fractional
differential equations.


title:
Search for single production of vector-like quarks decaying into $Wb$ in
  $pp$ collisions at $\sqrt{s} =$ 8 TeV with the ATLAS detector

abstract:
  A search for singly produced vector-like $Q$ quarks, where $Q$ can be either
a $T$ quark with charge $+2/3$ or a $Y$ quark with charge $-4/3$, is performed
in proton-proton collisions recorded with the ATLAS detector at the LHC. The
dataset corresponds to an integrated luminosity of 20.3 fb$^{-1}$ and was
produced with a centre-of-mass energy of $\sqrt{s}=8$ TeV. This analysis
targets $Q \to Wb$ decays where the $W$ boson decays leptonically. A veto on
massive large-radius jets is used to reject the dominant $t\bar{t}$ background.
The reconstructed $Q$-candidate mass, ranging from 0.4 to 1.2 TeV, is used in
the search to discriminate signal from background processes. No significant
deviation from the Standard Model expectation is observed, and limits are set
on the $Q \to Wb$ cross-section times branching ratio. The results are also
interpreted as limits on the $QWb$ coupling and the mixing with the Standard
Model sector for a singlet $T$ quark or a $Y$ quark from a doublet. $T$ quarks
with masses below 0.95 TeV are excluded at 95% confidence level, assuming a
unit coupling and a BR$(T\rightarrow Wb) = 0.5$, whereas the expected limit is
1.10 TeV.


title:
Global well-posedness and instability of an inhomogeneous nonlinear
  Schrodinger equation with harmonic potential

abstract:
  This paper is concerned with the Cauchy problem for an inhomogeneous
nonlinear Schrodinger equation with exponential growth nonlinearity and
harmonic potential in two space dimensions. We prove global well-posedness,
existence of the associated ground state and instability of the standing wave.


title: On the fine-grained complexity of rainbow coloring

abstract:
  The Rainbow k-Coloring problem asks whether the edges of a given graph can be
colored in $k$ colors so that every pair of vertices is connected by a rainbow
path, i.e., a path with all edges of different colors. Our main result states
that for any $k\ge 2$, there is no algorithm for Rainbow k-Coloring running in
time $2^{o(n^{3/2})}$, unless ETH fails.
  Motivated by this negative result we consider two parameterized variants of
the problem. In Subset Rainbow k-Coloring problem, introduced by Chakraborty et
al. [STACS 2009, J. Comb. Opt. 2009], we are additionally given a set $S$ of
pairs of vertices and we ask if there is a coloring in which all the pairs in
$S$ are connected by rainbow paths. We show that Subset Rainbow k-Coloring is
FPT when parameterized by $|S|$. We also study Maximum Rainbow k-Coloring
problem, where we are additionally given an integer $q$ and we ask if there is
a coloring in which at least $q$ anti-edges are connected by rainbow paths. We
show that the problem is FPT when parameterized by $q$ and has a kernel of size
$O(q)$ for every $k\ge 2$ (thus proving that the problem is FPT), extending the
result of Ananth et al. [FSTTCS 2011].


title: Fermionic influence (action) on inflationary fluctuations

abstract:
  Motivated by apparent persistent large scale anomalies in the CMB we study
the influence of fermionic degrees of freedom on the dynamics of inflaton
fluctuations as a possible source of violations of (nearly) scale invariance on
cosmological scales. We obtain the non-equilibrium effective action of an
inflaton-like scalar field with Yukawa interactions ($Y_{D,M}$) to light
\emph{fermionic} degrees of freedom both for Dirac and Majorana fields in de
Sitter space-time. The effective action leads to Langevin equations of motion
for the fluctuations of the inflaton-like field, with self-energy corrections
and a stochastic gaussian noise. We solve the Langevin equation in the
super-Hubble limit implementing a dynamical renormalization group resummation.
For a nearly massless inflaton its power spectrum of super Hubble fluctuations
is \emph{enhanced}, $\mathcal{P}(k;\eta) =
(\frac{H}{2\pi})^2\,e^{\gamma_t[-k\eta] }$ with $\gamma_t[-k\eta] =
\frac{1}{6\pi^2}
\Big[\sum_{i=1}^{N_D}{Y^2_{i,D}}+2\sum_{j=1}^{N_M}{Y^2_{j,M}}\Big]\,\Big\{\ln^2[-k\eta]-2
\ln[-k\eta]\ln[ -k\eta_0] \Big\} $ for $N_D$ Dirac and $N_M$ Majorana fermions,
and $\eta_0$ is the renormalization scale at which the inflaton mass vanishes.
The full power spectrum is shown to be renormalization group invariant. These
corrections to the super-Hubble power spectrum entail a violation of scale
invariance as a consequence of the coupling to the fermionic fields. The
effective action is argued to be \emph{exact} in a limit of large number of
fermionic fields. A cancellation between the enhancement from fermionic degrees
of freedom and suppression from light scalar degrees of freedom
\emph{conformally coupled to gravity} suggests the possibility of a finely
tuned \emph{supersymmetry} among these fields.


title: Closed Form for Some Gaussian Convolutions

abstract:
  The convolution of a function with an isotropic Gaussian appears in many
contexts such as differential equations, computer vision, signal processing,
and numerical optimization. Although this convolution does not always have a
closed form expression, there are important family of functions for which
closed form exists. This article investigates some of such cases.


title:
On the genesis of directional friction through bristle-like mediating
  elements

abstract:
  We propose an explanation of the genesis of directional dry friction, as
emergent property of the oscillations produced in a bristle-like mediating
element by the interaction with microscale fluctuations on the surface.
Mathematically, we extend a convergence result by Mielke, for
Prandtl-Tomlinson-like systems, considering also non-homothetic scalings of a
wiggly potential. This allows us to apply the result to some simple mechanical
models, that exemplify the interaction of a bristle with a surface having small
fluctuations. We find that the resulting friction is the product of two
factors: a geometric one, depending on the bristle angle and on the fluctuation
profile, and a energetic one, proportional to the normal force exchanged
between the bristle-like element and the surface. Finally, we apply our result
to discuss the with the nap/against the nap asymmetry.


title:
A comparison of NNLO QCD predictions with 7 TeV ATLAS and CMS data for
  $V$+jet processes

abstract:
  We perform a detailed comparison of next-to-next-to-leading order (NNLO) QCD
predictions for the W+jet and Z+jet processes with 7 TeV experimental data from
ATLAS and CMS. We observe excellent agreement between theory and data for most
studied observables, which span several orders of magnitude in both cross
section and energy. For some observables, such as the $H_T$ distribution, the
NNLO QCD corrections are essential for resolving existing discrepancies between
theory and data.


title: Mellin transforming the minimal model CFTs: AdS/CFT at strong curvature

abstract:
  Mack has conjectured that all conformal field theories are equivalent to
string theories. We explore the example of the two-dimensional minimal model
CFTs and confirm that the Mellin transformed amplitudes have the desired
properties of string theory in three-dimensional anti-de Sitter spacetime.


title: Rationality of dynamical canonical height

abstract:
  We present a dynamical proof of the well-known fact that the Neron-Tate
canonical height (and its local counterpart) takes rational values at points of
an elliptic curve over a function field k of transcendence degree 1 over an
algebraically closed field K of characteristic 0. More generally, we
investigate the mechanism for which the local canonical height for a rational
function f defined over k can take irrational values (at points in a local
completion of k), providing examples in all degrees greater than 1. Building on
Kiwi's classification of non-archimedean Julia sets for quadratic maps, we give
a complete answer in degree 2 characterizing the existence of points with
irrational local canonical heights. As an application of our results, we prove
that if the canonical heights of two points a and b under the action of two
rational functions f and g (defined over k) are positive rational numbers, and
if the degrees of f and g are multiplicatively independent, then the orbit of a
under f intersects the orbit of b under g in at most finitely many points,
complementing the results of Ghioca-Tucker-Zieve.


title:
Electronic torsional sound in linear atomic chains: chemical energy
  transport at 1000 km/s

abstract:
  We investigate entirely electronic torsional vibrational modes in linear
cumulene chains. The carbon nuclei of a cumulene are positioned along the
primary axis so they can participate only in transverse and longitudinal
motions. However, the interatomic electronic clouds behave as a torsion spring
with remarkable torsional stiffness. The collective dynamics of these clouds
can be described in terms of electronic vibrational quanta, which we name
torsitons. It is shown that the group velocity of the wavepacket of torsitons
is much higher than the typical speed of sound, because of the small mass of
participating electrons compared to the atomic mass. For the same reason the
maximum energy of the torsitons in cumulenes is as high as a few electronvolts,
while the minimum possible energy is evaluated as a few hundred wavenumbers and
this minimum is associated with asymmetry of zero point atomic vibrations.
Molecular systems for experimental evaluation of the predictions are proposed.


title: Student Difficulties with Quantum Mechanics Formalism

abstract:
  We discuss student difficulties in distinguishing between the physical space
and Hilbert space and difficulties related to the Time-independent Schroedinger
equation and measurements in quantum mechanics. These difficulties were
identified by administering written surveys and by conducting individual
interviews with students.


title:
Intermittency for the stochastic heat equation driven by a rough time
  fractional Gaussian noise

abstract:
  This paper studies the stochastic heat equation driven by time fractional
Gaussian noise with Hurst parameter $H\in(0,1/2)$. We establish the Feynman-Kac
representation of the solution and use this representation to obtain matching
lower and upper bounds for the $L^p(\Omega)$ moments of the solution.


title:
Testing Quality Requirements of a System-of-Systems in the Public Sector
  - Challenges and Potential Remedies

abstract:
  Quality requirements is a difficult concept in software projects, and testing
software qualities is a well-known challenge. Without proper management of
quality requirements, there is an increased risk that the software product
under development will not meet the expectations of its future users. In this
paper, we share experiences from testing quality requirements when developing a
large system-of-systems in the public sector in Sweden. We complement the
experience reporting by analyzing documents from the case under study. As a
final step, we match the identified challenges with solution proposals from the
literature. We report five main challenges covering inadequate requirements
engineering and disconnected test managers. Finally, we match the challenges to
solutions proposed in the scientific literature, including integrated
requirements engineering, the twin peaks model, virtual plumblines, the QUPER
model, and architecturally significant requirements. Our experiences are
valuable to other large development projects struggling with testing of quality
requirements. Furthermore, the report could be used by as input to process
improvement activities in the case under study.


title:
Cognitive Issues in Learning Advanced Physics: An Example from Quantum
  Mechanics

abstract:
  We are investigating cognitive issues in learning quantum mechanics in order
to develop effective teaching and learning tools. The analysis of cognitive
issues is particularly important for bridging the gap between the quantitative
and conceptual aspects of quantum mechanics and for ensuring that the learning
tools help students build a robust knowledge structure. We discuss the
cognitive aspects of quantum mechanics that are similar or different from those
of introductory physics and their implications for developing strategies to
help students develop a good grasp of quantum mechanics.


title:
The Golay Code Outperforms the Extended Golay Code Under Hard-Decision
  Decoding

abstract:
  We show that the binary Golay code is slightly more power efficient than the
extended binary Golay code under maximum-likelihood (ML), hard-decision
decoding. In fact, if a codeword from the extended code is transmitted, one
cannot achieve a higher probability of correct decoding than by simply ignoring
the 24th symbol and using an ML decoder for the non-extended code on the first
23 symbols. This is so, despite the fact that using that last symbol would
allow one to sometimes correct error patterns with weight four. To our
knowledge the worse performance of the extended Golay code has not been
previously noted, but it is noteworthy considering that it is the extended
version of the code that has been preferred in many deployments.


title: Universal N\'eron models for curves with marked points

abstract:
  We consider the problem of constructing universal N\'eron models for families
of curves with sections. By applying a construction of the author of universal
compactified Jacobians over the moduli stack of reduced curves with markings
and a result by J. Kass, we get a positive answer for smooth families of curves
with planar singularities over Dedekind schemes.


title: Compact Flow Diagrams for State Sequences

abstract:
  We introduce the concept of compactly representing a large number of state
sequences, e.g., sequences of activities, as a flow diagram. We argue that the
flow diagram representation gives an intuitive summary that allows the user to
detect patterns among large sets of state sequences. Simplified, our aim is to
generate a small flow diagram that models the flow of states of all the state
sequences given as input. For a small number of state sequences we present
efficient algorithms to compute a minimal flow diagram. For a large number of
state sequences we show that it is unlikely that efficient algorithms exist.
More specifically, the problem is W[1]-hard if the number of state sequences is
taken as a parameter. We thus introduce several heuristics for this problem. We
argue about the usefulness of the flow diagram by applying the algorithms to
two problems in sports analysis. We evaluate the performance of our algorithms
on a football data set and generated data.


title:
Coherent spin-light-induced mechanisms in the semi-relativistic limit of
  the self-consistent Dirac-Maxwell equations

abstract:
  We present a self-consistent mean-field model based on a two-component
Pauli-like equation that incorporates quantum and relativistic effects (up to
second-order in 1/c) for both external and internal electromagnetic fields. By
taking the semi-relativistic limit of the Dirac-Maxwell equations in the
presence of an external electromagnetic field we obtain an analytical
expression of a coherent light-induced mean-field Hamiltonian. The latter
exhibits several mechanisms that involve the internal mean fields created by
all the electrons and the external electromagnetic field (laser). The role
played by the light-induced current density and the light-induced second-order
charge density acting as sources in Maxwell's equations are clarified. In
particular, we identify clearly four different mechanisms involving the spins
that may play an important role in coherent ultrafast spin dynamics.


title: Simulating Infinite Vortex Lattices in Superfluids

abstract:
  We present an efficient framework to numerically treat infinite periodic
vortex lattices in rotating superfluids described by the Gross-Pitaevskii
theory. The commonly used split-step Fourier (SSF) spectral methods are
inapplicable to such systems as the standard Fourier transform does not respect
the boundary conditions mandated by the magnetic translation group. We present
a generalisation of the SSF method which incorporates the correct boundary
conditions by employing the so-called magnetic Fourier transform. We test the
method and show that it reduces to known results in the lowest-Landau-level
regime. While we focus on rotating scalar superfluids for simplicity, the
framework can be naturally extended to treat multicomponent systems and systems
under more general `synthetic' gauge fields.


title:
Green's function for elliptic systems: existence and Delmotte-Deuschel
  bounds

abstract:
  We prove that for an open domain $D \subset \mathbb{R}^d $ with $d \geq 2 $ ,
for every (measurable) uniformly elliptic tensor field $a$ and for almost every
point $y \in D$ , there exists a unique Green's function centred in $ y $
associated to the vectorial operator $ -\nabla \cdot a\nabla $ in D. In
particular, when $d > 2$ this result also implies the existence of the
fundamental solution for elliptic systems, i.e. the Green function for $
-\nabla \cdot a\nabla $ in $ \mathbb{R}^d $. Moreover, introducing an ensemble
$\langle\cdot \rangle$ over the set of uniformly elliptic tensor fields, under
the assumption of stationarity we infer for the fundamental solution $G$ some
pointwise bounds for $\langle |G(\cdot; x,y)|\rangle$, $\langle|\nabla_x
G(\cdot; x,y)|\rangle$ and $\langle |\nabla_x\nabla_y G(\cdot; x,y)|\rangle$.
These estimates scale optimally in space and provide a generalization to
systems of the bounds obtained by Delmotte and Deuschel for the scalar case.


title: On Douglas-Rachford operators that fail to be proximal mappings

abstract:
  The problem of finding a zero of the sum of two maximally monotone operators
is of central importance in optimization. One successful method to find such a
zero is the Douglas-Rachford algorithm which iterates a firmly nonexpansive
operator constructed from the resolvents of the given monotone operators. In
the context of finding minimizers of convex functions, the resolvents are
actually proximal mappings. Interestingly, as pointed out by Eckstein in 1989,
the Douglas-Rachford operator itself may fail to be a proximal mapping. We
consider the class of symmetric linear relations that are maximally monotone
and prove the striking result that the Douglas-Rachford operator is generically
not a proximal mapping.


title: The sands of time run faster near the end

abstract:
  Submerged granular hoppers exhibit an unexpected surge in discharge rate as
they empty [Wilson et al. 2015]. With a more sensitive apparatus, we find that
this surge depends on hopper diameter and also happens in air --- though the
effect is smaller and previously unnoticed. We also find that the surge may be
turned off by fixing the rate of fluid flow through the granular packing. With
no flow control, dye injected on top of the packing gets drawn into the grains,
at a rate that increases as the hopper empties. Thus we conclude that the surge
is caused by a self-generated pumping of fluid through the packing. We
successfully model this effect via a driving pressure set by the dilation of
grains as they exit. This highlights a surprising and unrecognized role that
interstitial fluid plays in setting the discharge rate, and likely also in
controlling clog formation, for granular hoppers whether in air or under water.


title:
Helping students learn effective problem solving strategies by
  reflecting with peers

abstract:
  We describe a study in which introductory physics students engage in
reflection with peers about problem solving. The recitations for an
introductory physics course with 200 students were broken into the "Peer
Reflection" (PR) group and the traditional group. Each week in recitation,
students in the PR group reflected in small teams on selected problems from the
homework and discussed why solutions of some students employed better problem
solving strategies than others. The graduate and undergraduate teaching
assistants (TAs) in the PR group recitations provided guidance and coaching to
help students learn effective problem solving heuristics. In the recitations
for the traditional group, students had the opportunity to ask the graduate TA
questions about the homework before they took a weekly quiz. The traditional
group recitation quiz questions were similar to the homework questions selected
for "peer reflection" in the PR group recitations. As one measure of the impact
of this intervention, we investigated how likely students were to draw diagrams
to help with problem solving. On the final exam with only multiple-choice
questions, the PR group drew diagrams on more problems than the traditional
group, even when there was no external reward for doing so. Since there was no
partial credit for drawing the diagrams on the scratch books, students did not
draw diagrams simply to get credit for the effort shown and must value the use
of diagrams for solving problems if they drew them. We also find that,
regardless of whether the students belonged to the traditional or PR groups,
those who drew more diagrams for the multiple-choice questions outperformed
those who did not draw them.


title:
Communication-Efficient Learning of Deep Networks from Decentralized
  Data

abstract:
  Modern mobile devices have access to a wealth of data suitable for learning
models, which in turn can greatly improve the user experience on the device.
For example, language models can improve speech recognition and text entry, and
image models can automatically select good photos. However, this rich data is
often privacy sensitive, large in quantity, or both, which may preclude logging
to the data center and training there using conventional approaches. We
advocate an alternative that leaves the training data distributed on the mobile
devices, and learns a shared model by aggregating locally-computed updates. We
term this decentralized approach Federated Learning.
  We present a practical method for the federated learning of deep networks
based on iterative model averaging, and conduct an extensive empirical
evaluation, considering five different model architectures and four datasets.
These experiments demonstrate the approach is robust to the unbalanced and
non-IID data distributions that are a defining characteristic of this setting.
Communication costs are the principal constraint, and we show a reduction in
required communication rounds by 10-100x as compared to synchronized stochastic
gradient descent.


title: Spectroscopic Binaries in the Orion Nebula Cluster and NGC 2264

abstract:
  We examine the spectroscopic binary population for two massive nearby regions
of clustered star formation, the Orion Nebula Cluster and NGC 2264,
supplementing the data presented by Tobin et al. (2009, 2015) with more recent
observations and more extensive analysis. The inferred multiplicity fraction up
to 10 AU based on these observations is $5.3\pm 1.2$% for NGC 2264 and $5.8\pm
1.1$% for the ONC; they are consistent with the distribution of binaries in the
field in the relevant parameter range. Eight of the multiple systems in the
sample have enough epochs to make an initial fit for the orbital parameters.
Two of these sources are double-lined spectroscopic binaries; for them we
determine the mass ratio. Our reanalysis of the distribution of stellar radial
velocities towards these clusters presents a significantly better agreement
between stellar and gas kinematics than was previously thought.


title: Heavy-tailed chiral random matrix theory

abstract:
  We study an unconventional chiral random matrix model with a heavy-tailed
probabilistic weight. The model is shown to exhibit chiral symmetry breaking
with no bilinear condensate, in analogy to the Stern phase of QCD. We solve the
model analytically and obtain the microscopic spectral density and the smallest
eigenvalue distribution for an arbitrary number of flavors and arbitrary quark
masses. Exotic behaviors such as non-decoupling of heavy flavors and a
power-law tail of the smallest eigenvalue distribution are illustrated.


title: Distributed Monitoring of Voltage Collapse Sensitivity Indices

abstract:
  The assessment of voltage stability margins is a promising direction for
wide-area monitoring systems. Accurate monitoring architectures for long-term
voltage instability are typically centralized and lack scalability, while
completely decentralized approaches relying on local measurements tend towards
inaccuracy. Here we present distributed linear algorithms for the online
computation of voltage collapse sensitivity indices. The computations are
collectively performed by processors embedded at each bus in the smart grid,
using synchronized phasor measurements and communication of voltage phasors
between neighboring buses. Our algorithms provably converge to the proper index
values, as would be calculated using centralized information, but but do not
require any central decision maker for coordination. Modifications of the
algorithms to account for generator reactive power limits are discussed. We
illustrate the effectiveness of our designs with a case study of the New
England 39 bus system.


title:
Observation of Unusual Topological Surface States in Half-Heusler
  Compounds LnPtBi (Ln=Lu, Y)

abstract:
  Topological quantum materials represent a new class of matter with both
exotic physical phenomena and novel application potentials. Many Heusler
compounds, which exhibit rich emergent properties such as unusual magnetism,
superconductivity and heavy fermion behaviour, have been predicted to host
non-trivial topological electronic structures. The coexistence of topological
order and other unusual properties makes Heusler materials ideal platform to
search for new topological quantum phases (such as quantum anomalous Hall
insulator and topological superconductor). By carrying out angle-resolved
photoemission spectroscopy (ARPES) and ab initio calculations on rare-earth
half-Heusler compounds LnPtBi (Ln=Lu, Y), we directly observed the unusual
topological surface states on these materials, establishing them as first
members with non-trivial topological electronic structure in this class of
materials. Moreover, as LnPtBi compounds are non-centrosymmetric
superconductors, our discovery further highlights them as promising candidates
of topological superconductors.


title:
The effect of anisotropic exchange interactions and short-range
  phenomena on superfluidity in a homogeneous dipolar Fermi gas

abstract:
  We develop a simple numerical method that allows us to calculate the
Bardeen-Cooper-Schriefer (BCS) superfluid transition temperature (Tc) precisely
for any interaction potential. We apply it to a polarised, ultracold Fermi gas
with long-range, anisotropic, dipolar interactions and include the effects of
anisotropic exchange interactions. We pay particular attention to the
short-range behaviour of dipolar gasses and re-examine current renormalisation
methods. In particular, we find that dimerisation of both atoms and molecules
significantly hampers the formation of a superfluid. The end result is that at
high density/interaction strengths, we find Tc is orders of magnitude lower
than previous calculations.


title: On the Power of Attribute-based Communication

abstract:
  In open systems, i.e. systems operating in an environment that they cannot
control and with components that may join or leave, behaviors can arise as side
effects of intensive components interaction. Finding ways to understand and
design these systems and, most of all, to model the interactions of their
components, is a difficult but important endeavor. To tackle these issues, we
present AbC, a calculus for attribute-based communication. An AbC system
consists of a set of parallel agents each of which is equipped with a set of
attributes. Communication takes place in an implicit multicast fashion, and
interactions among agents are dynamically established by taking into account
"connections" as determined by predicates over the attributes of agents. First,
the syntax and the semantics of the calculus are presented, then expressiveness
and effectiveness of AbC are demonstrated both in terms of modeling scenarios
featuring collaboration, reconfiguration, and adaptation and of the possibility
of encoding channel-based interactions and other interaction patterns.
Behavioral equivalences for AbC are introduced for establishing formal
relationships between different descriptions of the same system.


title:
Hydrodynamic study of edge spin-vortex excitations of fractional quantum
  Hall fluid

abstract:
  We undertake a theoretical study of edge spin-vortex excitations in
fractional quantum Hall fluid. This is done in view of quantised Euler
hydrodynamics theory. The dispersions of true excitations for fractions within
$0\leq \nu \leq 1$ are simulated which exhibit universal similarities and
differences in behaviour. The differences arise from different edge smoothness
and spin (pseudo-spin) polarisations, in addition to spin-charge competition.
In particular, tuning the spin-charge factor causes coherent spin flipping
associated with partial and total polarisations of edge spin-vortices. This
observation is tipped as an ideal mechanism for realisation of functional
spintronic devices.


title: Effective quasimorphisms on right-angled Artin groups

abstract:
  We construct new families of quasimorphisms on many groups acting on CAT(0)
cube complexes. These quasimorphisms have a uniformly bounded defect of 12, and
they "see" all elements that act hyperbolically on the cube complex. We deduce
that all such elements have stable commutator length at least 1/24.
  The group actions for which these results apply include the standard actions
of right-angled Artin groups on their associated CAT(0) cube complexes. In
particular, every non-trivial element of a right-angled Artin group has stable
commutator length at least 1/24.
  These results make use of some new tools that we develop for the study of
group actions on CAT(0) cube complexes: the essential characteristic set and
equivariant Euclidean embeddings.


title:
Memory-Centred Cognitive Architectures for Robots Interacting Socially
  with Humans

abstract:
  The Memory-Centred Cognition perspective places an active association
substrate at the heart of cognition, rather than as a passive adjunct.
Consequently, it places prediction and priming on the basis of prior experience
to be inherent and fundamental aspects of processing. Social interaction is
taken here to minimally require contingent and co-adaptive behaviours from the
interacting parties. In this contribution, I seek to show how the
memory-centred cognition approach to cognitive architectures can provide an
means of addressing these functions. A number of example implementations are
briefly reviewed, particularly focusing on multi-modal alignment as a function
of experience-based priming. While there is further refinement required to the
theory, and implementations based thereon, this approach provides an
interesting alternative perspective on the foundations of cognitive
architectures to support robots engage in social interactions with humans.


title:
Experimental realization of the "lock-and-key" mechanism in liquid
  crystals

abstract:
  The ability to control the movement and assembly of particles in liquid
crystals is not only an important route to design functional materials, but
also sheds light on the mechanisms of colloidal interactions. In this study we
place micron-sized particles with "Saturn ring" defects near a wall with hills
and dales that impose perpendicular (homeotropic) molecular anchoring. The
strong splay distortion at the wall interacts with the distortion around the
particles in the near field and favors their migration towards the dales via
the so-called "lock-and-key" mechanism. We demonstrate experimentally that the
lock-and-key mechanism can robustly localize a particle at specific
topographical features. We observe the complex trajectories traced by the
particles as they dock on the dales, estimate the binding energy, and explore a
range of parameters that favor or disfavor the docking event, thus exploiting
the capabilities of our experimental system. We extend the study to colloids
with homeotropic anchoring but with an associated point defect instead of a
Saturn ring and show that they find a different preferred location, i.e. we can
place otherwise identical particles at well defined sites according to their
topological defect structure. Finally, for deep enough wells, confinement
drives topological transitions of Saturn rings to dipoles. This ability to
tailor wall geometry to guide colloids to well defined sites within nematic
liquid crystals represents an important new tool in directed assembly.


title: Superfluid Brillouin Optomechanics

abstract:
  Optomechanical systems couple an electromagnetic cavity to a mechanical
resonator which is typically formed from a solid object. The range of phenomena
accessible to these systems depends on the properties of the mechanical
resonator and on the manner in which it couples to the cavity fields. In both
respects, a mechanical resonator formed from superfluid liquid helium offers
several appealing features: low electromagnetic absorption, high thermal
conductivity, vanishing viscosity, well-understood mechanical loss, and in situ
alignment with cryogenic cavities. In addition, it offers degrees of freedom
that differ qualitatively from those of a solid. Here, we describe an
optomechanical system consisting of a miniature optical cavity filled with
superfluid helium. The cavity mirrors define optical and mechanical modes with
near-perfect overlap, resulting in an optomechanical coupling rate ~3 kHz. This
coupling is used to drive the superfluid; it is also used to observe the
superfluid's thermal motion, resolving a mean phonon number as low as 11.


title:
Exponents for the number of pairs of ${\alpha}$-favorite points of
  simple random walk in ${\mathbb Z}^2$

abstract:
  We investigate a problem suggested by Dembo, Peres, Rosen, and Zeitouni,
which states that the growth exponent of favorite points associated with a
simple random walk in ${\mathbb Z}^2$ coincides, on average and almost surely,
with those of late points and high points associated with the discrete Gaussian
free field.


title:
When the Filter Bubble Bursts: Collective Evaluation Dynamics in Online
  Communities

abstract:
  We analyze online collective evaluation processes through positive and
negative votes in various social media. We find two modes of collective
evaluations that stem from the existence of filter bubbles. Above a threshold
of collective attention, negativity grows faster with positivity, as a sign of
the burst of a filter bubble when information reaches beyond the local social
context of a user. We analyze how collectively evaluated content can reach
large social contexts and create polarization, showing that emotions expressed
through text play a key role in collective evaluation processes.

categories: cs.SI physics.data-an physics.soc-ph stat.AP


title:
An Analysis of the Search Spaces for Generate and Validate Patch
  Generation Systems

abstract:
  We present the first systematic analysis of the characteristics of patch
search spaces for automatic patch generation systems. We analyze the search
spaces of two current state-of-the-art systems, SPR and Prophet, with 16
different search space configurations. Our results are derived from an analysis
of 1104 different search spaces and 768 patch generation executions. Together
these experiments consumed over 9000 hours of CPU time on Amazon EC2.
  The analysis shows that 1) correct patches are sparse in the search spaces
(typically at most one correct patch per search space per defect), 2) incorrect
patches that nevertheless pass all of the test cases in the validation test
suite are typically orders of magnitude more abundant, and 3) leveraging
information other than the test suite is therefore critical for enabling the
system to successfully isolate correct patches.
  We also characterize a key tradeoff in the structure of the search spaces.
Larger and richer search spaces that contain correct patches for more defects
can actually cause systems to find fewer, not more, correct patches. We
identify two reasons for this phenomenon: 1) increased validation times because
of the presence of more candidate patches and 2) more incorrect patches that
pass the test suite and block the discovery of correct patches. These
fundamental properties, which are all characterized for the first time in this
paper, help explain why past systems often fail to generate correct patches and
help identify challenges, opportunities, and productive future directions for
the field.


title:
A relativistic description of MOND using the Palatini formalism in an
  extended metric theory of gravity

abstract:
  We construct a relativistic metric description of MOND using the Palatini
formalism following the \( f(\chi)=\chi^b \) description of
\citet{mendozatula}. We show that in order to recover the non-relativistic MOND
regime where, for circular orbits the Tully-Fisher law replaces Kepler's third
law, the value of the parameter $ b = 3/2 $, which is coincident with the value
found using a pure metric formalism Capozziello et al. (2011). Unlike the pure
metric formalism, which yields 4th order field equations, the Palatini approach
yields second order field equations, which is a desirable requirement from a
theoretical perspective. Thus, the phenomenology associated to astrophysical
phenomena with Tully-Fisher scalings can be accounted for using this proposal,
without the need to introduce any non-baryonic dark matter particles.


title: Unimodular Mimetic $F(R)$ Inflation

abstract:
  We propose the unimodular-mimetic $F(R)$ gravity theory, to resolve
cosmological constant problem and dark matter problem in a unified geometric
manner. We demonstrate that such a theory naturally admits accelerating
universe evolution. Furthermore, we construct unimodular-mimetic $F(R)$
inflationary cosmological scenarios compatible with the Planck and
BICEP2/Keck-Array observational data. We also address the graceful exit issue,
which is guaranteed by the existence of unstable de Sitter vacua.


title: Recollements, sinks elimination and Leavitt path algebras

abstract:
  For Leavitt path algebras, we show that whereas removing sources from a graph
produces a Morita equivalence, removing sinks gives rise to a recollement
situation. In general, we show that for a graph $E$ and a finite hereditary
subset $H$ of $E^0$ there is a recollement $$\xymatrix{ L_K(E/\overline H)
\rModd \ar[r] & \ar@<3pt>[l] \ar@<-3pt>[l] L_K(E) \rModd \ar[r] & \ar@<3pt>[l]
\ar@<-3pt>[l] L_K(E_H) \rModd .}$$ We record several corollaries.


title: Cocycle conjugacy classes of binary shifts

abstract:
  We show that every binary shift on the hyperfinite $II_1$ factor $R$ is
cocycle conjugate to at least countably many non-conjugate binary shifts. This
holds in particular for binary shifts of infinite commutant index.


title:
NICA fixed target mode: soft jet studies in the relative 4-velocity
  space

abstract:
  Experimental results obtained by studying the properties of soft jets in the
4-velocity space at $\sqrt{s} \sim 2-20$ GeV are presented. The changes in the
mean distance from the jet axis to the jet particles, the mean kinetic energy
of these particles, and the cluster dimension in response to the growth of the
collision energy are consistent with the assumption that quark degrees of
freedom manifest themselves in processes of pion jet production at intermediate
energies. The energy at which quark degrees of freedom begin to manifest
themselves experimentally in the production of soft pion jets is estimated for
the first time. The estimated value of this energy is $2.8 \pm 0.6$ GeV. The
suggestions are made for future investigations on NICA.


title: The Information Capacity of Specific Interactions

abstract:
  Specific interactions are a hallmark feature of self-assembly and
signal-processing systems in both synthetic and biological settings.
Specificity between components may arise from a wide variety of physical and
chemical mechanisms in diverse contexts, from DNA hybridization to
shape-sensitive depletion interactions. Despite this diversity, all systems
that rely on interaction specificity operate under the constraint that
increasing the number of distinct components inevitably increases off-target
binding. Here we introduce `capacity', the maximal information encodable using
specific interactions, to compare specificity across diverse experimental
systems, and to compute how specificity changes with physical parameters. Using
this framework, we find that `shape'-coding of interactions has higher capacity
than chemical (`color') coding because the strength of off-target binding is
strongly sublinear in binding site size for shapes while being linear for
colors. We also find that different specificity mechanisms, such as shape and
color, can be combined in a synergistic manner, giving a capacity greater than
the sum of the parts.


title:
A fast platform for simulating flexible fiber suspensions applied to
  cell mechanics

abstract:
  We present a novel platform for the large-scale simulation of fibrous
structures immersed in a Stokesian fluid and evolving under confinement or in
free-space. One of the main motivations for this work is to study the dynamics
of fiber assemblies within biological cells. For this, we also incorporate the
key biophysical elements that determine the dynamics of these assemblies, which
include the polymerization and depolymerization kinetics of fibers, their
interactions with molecular motors and other objects, their flexibility, and
hydrodynamic coupling.
  This work, to our knowledge, is the first technique to include many-body
hydrodynamic interactions (HIs), and the resulting fluid flows, in cellular
fiber assemblies. We use the non-local slender body theory to compute the
fluid-structure interactions of the fibers and a second-kind boundary integral
formulation for other rigid bodies and the confining boundary. A
kernel-independent implementation of the fast multiple method is utilized for
efficient evaluation of HIs. The deformation of the fibers is described by the
nonlinear Euler--Bernoulli beam theory and their polymerization is modeled by
the reparametrization of the dynamic equations in the appropriate
non-Lagrangian frame. We use a pseudo-spectral representation of fiber
positions and implicit HIs in the time-stepping to resolve large fiber
deformations, and to allow time-steps not constrained by temporal stiffness or
fiber-fiber interactions. The entire computational scheme is parallelized,
which enables simulating assemblies of thousands of fibers. We use our method
to investigate two important questions in the mechanics of cell division: (i)
the effect of confinement on the hydrodynamic mobility of microtubule asters;
and (ii) the dynamics of the positioning of mitotic spindle in complex cell
geometries.


title:
Experimental realization of the Yang-Baxter Equation via NMR
  interferometry

abstract:
  The Yang-Baxter equation is an important tool in theoretical physics, with
many applications in different domains that span from condensed matter to
string theory. Recently, the interest on the equation has increased due to its
connection to quantum information processing. It has been shown that the
Yang-Baxter equation is closely related to quantum entanglement and quantum
computation. Therefore, owing to the broad relevance of this equation, besides
theoretical studies, it also became significant to pursue its experimental
implementation. Here, we show an experimental realization of the Yang-Baxter
equation and verify its validity through a Nuclear Magnetic Resonance (NMR)
interferometric setup. Our experiment was performed on a liquid state
Iodotrifluoroethylene sample which contains molecules with three qubits. We use
Controlled-transfer gates that allow us to build a pseudo-pure state from which
we are able to apply a quantum information protocol that implements the
Yang-Baxter equation.


title: The effect of base pair mismatch on DNA strand displacement

abstract:
  DNA strand displacement is a key reaction in DNA homologous recombination and
DNA mismatch repair and is also heavily utilized in DNA-based computation and
locomotion. Despite its ubiquity in science and engineering, sequence-dependent
effects of displacement kinetics have not been extensively characterized. Here,
we measured toehold-mediated strand displacement kinetics using single-molecule
fluorescence in the presence of a single base pair mismatch. The apparent
displacement rate varied significantly when the mismatch was introduced in the
invading DNA strand. The rate generally decreased as the mismatch in the
invader was encountered earlier in displacement. Our data indicate that a
single base pair mismatch in the invader stalls branch migration, and
displacement occurs via direct dissociation of the destabilized incumbent
strand from the substrate strand. We combined both branch migration and direct
dissociation into a model, which we term, the concurrent displacement model,
and used the first passage time approach to quantitatively explain the salient
features of the observed relationship. We also introduce the concept of
splitting probabilities to justify that the concurrent model can be simplified
into a three-step sequential model in the presence of an invader mismatch. We
expect our model to become a powerful tool to design DNA-based reaction schemes
with broad functionality.


title: NICA-MPD: azimuthal and femtoscopic particle correlations

abstract:
  The discussion is focused on the study of the fundamental symmetries
($\mathcal{P/CP}$) of QCD and geometry of the particle source. The combination
of correlators corresponding to the absolute asymmetry of distribution of
electrically charged particles with respect to the reaction plane in heavy ion
collisions is studied. A significant decrease of the absolute asymmetry is
observed in the intermediate energy range which can be considered as indication
of possible transition to predominance of hadronic states over quark-gluon
degrees of freedom in the mixed phase created in heavy ion collisions at
intermediate energies. For the investigation of the energy evolution of the
geometric properties of the particle source the use of femtoscopic radii scaled
on the averaged radius of colliding ions is suggested. This approach allows the
expansion of the set of interaction types, in particular, on the collisions of
non-symmetrical ion beams which can be studied within the framework of common
treatment. There is no sharp changing of femtoscopic parameter values with
increasing of the initial energy. The suggestions are made for future
advancement of these studies on NICA-MPD.


title:
Detecting Majorana fermions by use of superconductor-quantum Hall liquid
  junctions

abstract:
  The point contact tunnel junctions between a one-dimensional topological
superconductor and single-channel quantum Hall (QH) liquids are investigated
theoretically with bosonization technology and renormalization group methods.
For the $\nu=1$ integer QH liquid, the universal low-energy tunneling transport
is governed by the perfect Andreev reflection fixed point with quantized
zero-bias conductance $G(0)=2e^{2}/h$, which can serve as a definitive
fingerprint of the existence of a Majorana fermion. For the $\nu =1/m$ Laughlin
fractional QH liquids, its transport is governed by the perfect normal
reflection fixed point with vanishing zero-bias conductance and bias-dependent
conductance $G(V) \sim V^{m-2}$. Our setup is within reach of present
experimental techniques.


title: Transfer of Learning in Quantum Mechanics

abstract:
  We investigate the difficulties that undergraduate students in quantum
mechanics courses have in transferring learning from previous courses or within
the same course from one context to another by administering written tests and
conducting individual interviews. Quantum mechanics is abstract and its
paradigm is very different from the classical one. A good grasp of the
principles of quantum mechanics requires creating and organizing a knowledge
structure consistent with the quantum postulates. Previously learned concepts
such as the principle of superposition and probability can be useful in quantum
mechanics if students are given opportunity to build associations between new
and prior knowledge. We also discuss the need for better alignment between
quantum mechanics and modern physics courses taken previously because
semi-classical models can impede internalization of the quantum paradigm in
more advanced courses.


title: An Estimation Method Using Periodic Inspection of Indicators

abstract:
  This paper proposes a new approach for estimating the failure time
distribution using the indicator data. The indicators, which are checked by
periodic inspection of a standby redundant system, only convey whether at least
one failure occurs per interval. The estimation procedure first obtains the
estimation of the forward recurrence time using the indicator data. Then the
mean is estimated based on its relationship with the forward recurrence time.
And the estimation of the sampled Cdf is thus derived based on its relationship
with the forward recurrence time and the mean. Finally, the Cdf function is
estimated using interpolation method. The simulation results showed that the
estimation method performed well for the four Weibull distributions.


title: The Computational Complexity of the Frobenius Problem

abstract:
  In this paper, as a main theorem, we prove that the decision version of the
Frobenius problem is Sigma_2^P-complete under Karp reductions.Given a finite
set A of coprime positive integers, we call the greatest integer that cannot be
represented as a nonnegative integer combination of A the Frobenius number, and
we denote it as g(A). We call a problem of finding g(A) for a given A the
Frobenius problem; moreover, we call a problem of determining whether g(A) >= k
for a given pair (A, k) the decision version of the Frobenius problem, where A
is a finite set of coprime positive integers and k is a positive integer. For
the proof, we construct two Karp reductions. First, we reduce a 2-alternating
version of the 3-dimensional matching problem, which is known to be
Pi_2^P-complete, to a 2-alternating version of the integer knapsack problem.
Then, we reduce the variant of the integer knapsack problem to the complement
of the decision version of the Frobenius problem. As a corollary, we obtain the
main theorem.


title:
Averaging principle for non autonomous slow-fast systems of stochastic
  RDEs: the almost periodic case

abstract:
  We study the validity of an averaging principle for a slow-fast system of
stochastic reaction diffusion equations. We assume here that the coefficients
of the fast equation depend on time, so that the classical formulation of the
averaging principle in terms of the invariant measure of the fast equation is
not anymore available. As an alternative, we introduce the time depending
evolution family of measures associated with the fast equation. Under the
assumption that the coefficients in the fast equation are almost periodic, the
evolution family of measures is almost periodic. This allows to identify the
appropriate averaged equation and prove the validity of the averaging limit.


title:
Boost Picking: A Universal Method on Converting Supervised
  Classification to Semi-supervised Classification

abstract:
  This paper proposes a universal method, Boost Picking, to train supervised
classification models mainly by un-labeled data. Boost Picking only adopts two
weak classifiers to estimate and correct the error. It is theoretically proved
that Boost Picking could train a supervised model mainly by un-labeled data as
effectively as the same model trained by 100% labeled data, only if recalls of
the two weak classifiers are all greater than zero and the sum of precisions is
greater than one. Based on Boost Picking, we present "Test along with Training
(TawT)" to improve the generalization of supervised models. Both Boost Picking
and TawT are successfully tested in varied little data sets.


title: Feature-Area Optimization: A Novel SAR Image Registration Method

abstract:
  This letter proposes a synthetic aperture radar (SAR) image registration
method named Feature-Area Optimization (FAO). First, the traditional area-based
optimization model is reconstructed and decomposed into three key but uncertain
factors: initialization, slice set and regularization. Next, structural
features are extracted by scale invariant feature transform (SIFT) in
dual-resolution space (SIFT-DRS), a novel SIFT-Like method dedicated to FAO.
Then, the three key factors are determined based on these features. Finally,
solving the factor-determined optimization model can get the registration
result. A series of experiments demonstrate that the proposed method can
register multi-temporal SAR images accurately and efficiently.


title:
Optimal control problems of forward-backward stochastic Volterra
  integral equations with closed control regions

abstract:
  Optimal control problems of forward-backward stochastic Volterra integral
equations (FBSVIEs, in short) with closed control regions are formulated and
studied. Instead of using spike variation method as one may imagine, here we
turn to treat the non-convexity of the control regions by borrowing some tools
in set-valued analysis and adapting them into our stochastic control systems. A
duality principle between linear backward stochastic Volterra integral
equations and linear stochastic Fredholm-Volterra integral equations with
conditional expectation are derived, which extends and improves the
corresponding results in [25], [30]. Some first order necessary optimality
conditions for optimal controls of FBSVIEs are established. In contrast with
existed common routines to treat the non-convexity of stochastic control
problems, here only one adjoint system and one-order differentiability
requirements of the coefficients are needed.


title:
On the Hausdorff dimension faithfulness connected with
  $Q_{infty}$-expansion

abstract:
  In this paper, we show that, the family of all possible union of finite
consecutive cylinders of the same rank of $Q_{\infty}$-expansion is faithful
for the Hausdorff dimension calculation. Applying this result, we give the
necessary and sufficient condition for the family of all cylinders of
$Q_{\infty}$-expansion to be faithful for Hausdorff dimension calculation on
the unit interval, this answers the open problem mentioned in a paper of S.
Albeverio et al..


title: Endpoint estimates for one-dimensional oscillatory integral operator

abstract:
  The one-dimensional oscillatory integral operator associated to a real
analytic phase $S$ is given by $$ T_\lambda f(x) =\int_{-\infty}^\infty
e^{i\lambda S(x,y)} \chi(x,y) f(y) dy. $$ In this paper, we obtain a complete
characterization for the mapping properties of $T_\lambda $ on $L^p(\mathbb R)$
spaces, namely we prove that $\|T_\lambda\|_p \lesssim
|\lambda|^{-\alpha}\|f\|_p$ for some $\alpha>0$ if and only if the point
$(\frac 1 {\alpha p} , \frac 1 {\alpha p'})$ lies in the reduced Newton polygon
of $S$, and this estimate is sharp if and only if it lies on the reduced Newton
diagram.


title: Assessing and improving student understanding of quantum mechanics

abstract:
  We developed a survey to probe student understanding of quantum mechanics
concepts at the beginning of graduate instruction. The survey was administered
to 202 graduate students in physics enrolled in first-year quantum mechanics
courses from seven different universities at the beginning of the first
semester. We also conducted one-on-one interviews with fifteen graduate
students or advanced undergraduate students who had just finished a course in
which all the content on the survey was covered. We find that students share
universal difficulties about fundamental quantum mechanics concepts. The
difficulties are often due to over-generalization of concepts learned in one
context to other contexts where they are not directly applicable and difficulty
in making sense of the abstract quantitative formalism of quantum mechanics.
Instructional strategies that focus on improving student understanding of these
concepts should take into account these difficulties. The results from this
study can sensitize instructors of first-year graduate quantum physics to the
conceptual difficulties students are likely to face.


title:
Incorporating Hierarchical Structure Into Dynamic Systems: An
  Application Of Estimating HIV Epidemics At Sub-National And Sub-Population
  Level

abstract:
  Dynamic models have been successfully used in producing estimates of HIV
epidemics at national level, due to their epidemiological nature and their
ability to simultaneously estimate prevalence, incidence, and mortality rates.
Recently, HIV interventions and policies have required more information at
sub-national and sub-population levels to support local planning, decision
making and resource allocation. Unfortunately, many areas and high-risk groups
lack sufficient data for deriving stable and reliable results, and this is a
critical technical barrier to more stratified estimates. One solution is to
borrow information from other areas and groups within the same country.
However, directly assuming hierarchical structures within the HIV dynamic
models is complicated and computationally time consuming. In this paper, we
propose a simple and innovative way to incorporate the hierarchical information
into the dynamic systems by using auxiliary data. The proposed method
efficiently uses information from multiple areas and risk groups within each
country without increasing the computational burden. As a result, the new model
improves predictive ability in general with especially significant improvement
in areas and risk groups with sparse data.


title: Early universe thermostatistics in curved momentum spaces

abstract:
  The theories known as doubly special relativity are introduced in order to
take into account an observer-independent length scale and the speed of light
in the framework of special relativity. These theories can be generally
formulated on the de Sitter and also recently proposed anti-de Sitter momentum
spaces. In the context of these theories, we study the statistical mechanics
and to do this, we consider the natural measure on the corresponding extended
phase space. The invariant measure on the space of distinct microstates is
obtained by restriction of the natural measure of the extended phase space to
the physical phase space through the disintegration theorem. Having the
invariant measure, one can study the statistical mechanics in an arbitrary
ensemble for any doubly special relativity theory. We use the constructed setup
to study the statistical properties of four doubly special relativity models.
Applying the results to the case of early universe thermodynamics, we show that
one of these models that is defined by the cosmological coordinatization of
anti-de Sitter momentum space, implies a finite total number of microstates.
Therefore, without attribution to any ensemble density and quite generally, we
obtain entropy and internal energy bounds for the early radiation dominated
universe. We find that while these results cannot be supported by the standard
Friedmann equations, they indeed are in complete agreement with the nonsingular
effective Friedmann equations that arise in the context of loop quantum
cosmology.


title:
Towards numerically robust multireference theories: The driven
  similarity renormalization group truncated to one- and two-body operators

abstract:
  The first nonperturbative version of the multireference driven similarity
renormalization group (MR-DSRG) theory [C. Li and F. A. Evangelista, J. Chem.
Theory Comput. $\mathbf{11}$, 2097 (2015)] is introduced. The renormalization
group structure of the MR-DSRG equations ensures numerical robustness and
avoidance of the intruder state problem, while the connected nature of the
amplitude and energy equations guarantees size consistency and extensivity. We
approximate the MR-DSRG equations by keeping only one- and two-body operators
and using a linearized recursive commutator approximation of the
Baker--Campbell--Hausdorff expansion [T. Yanai and G. K.-L. Chan, J. Chem.
Phys. $\mathbf{124}$, 194106 (2006)]. The resulting MR-LDSRG(2) equations
contain only 39 terms and scales as ${\cal O}(N^2 N_{\rm P}^2 N_{\rm H}^2)$
where $N_{\rm H}$, $N_{\rm P}$, and $N$ correspond to the number of hole,
particle, and total orbitals, respectively. Benchmark MR-LDSRG(2) computations
on the hydrogen fluoride and molecular nitrogen binding curves and the
singlet-triplet splitting of $p$-benzyne yield results comparable in accuracy
to those from multireference configuration interaction, Mukherjee
multireference coupled cluster theory, and internally-contracted multireference
coupled cluster theory.


title:
Attosecond Interference Induced by Coulomb-Field-Driven Transverse
  Backward-Scattering Electron Wave-Packets

abstract:
  A novel and universal interference structure is found in the photoelectron
momentum distribution of atoms in intense infrared laser field. Theoretical
analysis shows that this structure can be attributed to a new form of
Coulomb-field-driven backward-scattering of photoelectrons in the direction
perpendicular to the laser field, in contrast to the conventional rescattering
along the laser polarization direction. This transverse backward-scattering
process is closely related to a family of photoelectrons initially ionized
within a time interval of less than 200 attosecond around the crest of the
laser electric field. Those electrons, acquiring near-zero return energy in the
laser field, will be pulled back solely by the ionic Coulomb field and
backscattered in the transverse direction. Moreover, this rescattering process
mainly occurs at the first or the second return times, giving rise to different
phases of the photoelectrons. The interference between these photoelectrons
leads to unique curved interference fringes which are observable for most
current intense field experiments, opening a new way to record the electron
dynamics in atoms and molecules on a time scale much shorter than an optical
cycle.


title:
A note on injectivity of Frobenius on local cohomology of global
  complete intersections

abstract:
  Given a graded complete intersection ideal $J = (f_1, \dots, f_c) \subseteq
k[x_0, \dots, x_n] = S$, where $k$ is a field of characteristic $p > 0$ such
that $[k:k^p] < \infty$, we show that if $S/J$ has an isolated non-F-pure point
then the Frobenius action on top local cohomology $H^{n+1-c}_\mathfrak{m}(S/J)$
is injective in sufficiently negative degrees, and we compute the least degree
of any kernel element. If $S/J$ has an isolated singularity, we are also able
to give an effective bound on $p$ ensuring the Frobenius action on
$H^{n+1-c}_\mathfrak{m}(S/J)$ is injective in all negative degrees, extending a
result of Bhatt and Singh in the hypersurface case.


title: Military Strategy in a Complex World

abstract:
  A strategy is a plan, method, or series of actions for obtaining a specified
goal. A military strategy typically employs the threat or use of military force
in opposition to an adversary, and is called upon where large scale force is
viewed as the way to achieve such goals. Strategic thinking is traditionally
focused on which part or combination of land, air, and naval forces is most
effective. This may be too narrow an approach to accomplishing the ultimate
end, which is generally political influence or control--or preventing influence
or control by others--and almost never consists of physical destruction itself.
In order to broaden the discussion of military strategy, we consider here three
distinct effects of inflicting stress on an opponent: a) A fragile system is
damaged--possibly catastrophically, b) A robust system is largely unaffected,
retaining much or all of its prior strength, c) Some systems actually gain
strength, a property which has recently been termed antifragility. Traditional
perspectives of military strategy implicitly assume fragility, limiting their
validity and resulting in surprise, and assume a specific end state rather than
an overall condition of the system as a goal. Robustness and antifragility are
relevant both to offense and defense. While robustness and antifragility are
desirable in friendly systems, an enemy possessing these characteristics
undermines the premise that an attack will achieve a desired increase in
control. Historical and contemporary examples demonstrate the failure of
traditional strategies against antifragile enemies--even devastating damage
inflicted upon nations or other organizations did not weaken and defeat them,
but rather strengthened them, resulting in their victory. Underlying such
successful responses are socio-economic or political strengths. Our discussion
is a basis for scientific analysis of improved strategic thinking.