title:
Two-Gluon Correlations in Heavy-Light Ion Collisions: Energy and
  Geometry Dependence, IR Divergences, and $k_T$-Factorization

abstract:
  We study the properties of the cross section for two-gluon production in
heavy-light ion collisions derived in our previous paper on the subject in the
saturation/Color Glass Condensate framework. Concentrating on the energy and
geometry dependence of the corresponding correlation functions we find that the
two-gluon correlator is a much slower function of the center-of-mass energy
than the one- and two-gluon production cross sections. The geometry dependence
of the correlation function leads to stronger azimuthal near- and away-side
correlations in the tip-on-tip U+U collisions than in the side-on-side U+U
collisions, an exactly opposite behavior from the correlations generated by the
elliptic flow of the quark-gluon plasma: a study of azimuthal correlations in
the U+U collisions may thus help to disentangle the two sources of
correlations.
  We demonstrate that the cross section for two-gluon production in heavy-light
ion collisions contains a power-law infrared (IR) divergence even for fixed
produced gluon momenta: while saturation effects in the target regulate some of
the power-law IR-divergent terms in the lowest-order expression for the
two-gluon correlator, other power-law IR-divergent terms remain, possibly due
to absence of saturation effects in the dilute projectile. Finally we rewrite
our result for the two-gluon production cross-section in a $k_T$-factorized
form, obtaining a new factorized expression involving a convolution of one- and
two-gluon Wigner distributions over both the transverse momenta and impact
parameters. We show that the two-gluon production cross-section depends on two
different types of unintegrated two-gluon Wigner distribution functions.


title: Relativistic Achilles

abstract:
  This manuscript presents a problem on special relativity theory (SRT) which
embodies an apparent paradox relying on the concept of simultaneity. The
problem is represented in the framework of Greek epic poetry and structured in
a didactic way. Owing to the characteristic properties of Lorenz
transformations, three events which are simultaneous in a given inertial
reference system, occur at different times in the other two reference frames.
In contrast to the famous twin paradox, in the present case there are three,
not two, different inertial observers. This feature provides a better framework
to expose some of the main characteristics of SRT, in particular, the concept
of velocity and the relativistic rule of addition of velocities.


title: Injectivity and univalence of complex functions via monotonicity

abstract:
  In this paper we provide sufficient conditions that ensure the monotonicity,
respectively the global injectivity of an operator. Further, some new
analytical conditions that assure the injectivity/univalence of a complex
function of one complex variable are obtained. We also show that some classical
results, such as Alexander-Noshiro-Warschawski and Wolff theorem or Mocanu
theorem, are easy consequences of our results.


title:
A Hierarchical Dynamic Programming Algorithm for Optimal Coalition
  Structure Generation

abstract:
  We present a new Dynamic Programming (DP) formulation of the Coalition
Structure Generation (CSG) problem based on imposing a hierarchical
organizational structure over the agents. We show the efficiency of this
formulation by deriving DyPE, a new optimal DP algorithm which significantly
outperforms current DP approaches in speed and memory usage. In the classic
case, in which all coalitions are feasible, DyPE has half the memory
requirements of other DP approaches. On graph-restricted CSG, in which
feasibility is restricted by a (synergy) graph, DyPE has either the same or
lower computational complexity depending on the underlying graph structure of
the problem. Our empirical evaluation shows that DyPE outperforms the
state-of-the-art DP approaches by several orders of magnitude in a large range
of graph structures (e.g. for certain scalefree graphs DyPE reduces the memory
requirements by $10^6$ and solves problems that previously needed hours in
minutes).


title: Universal unramified cohomology of cubic fourfolds containing a plane

abstract:
  We prove the universal triviality of the third unramified cohomology group of
a very general complex cubic fourfold containing a plane. The proof uses
results on the unramified cohomology of quadrics due to Kahn, Rost, and
Sujatha.


title:
Numerical study of the Yang-Mills vacuum wavefunctional in D=3+1
  dimensions

abstract:
  Ratios of the true Yang-Mills vacuum wavefunctional, evaluated on any two
field configurations out of a finite set of configurations, can be obtained
from lattice Monte Carlo simulations. The method was applied some years ago to
test various proposals for the vacuum wavefunctional in 2+1 dimensions. In this
article we use the same method to test our own proposal for the Yang-Mills
ground state in 3+1 dimensions. This state has the property of "dimensional
reduction" at large scales, meaning that the (squared) vacuum state, evaluated
on long-wavelength, large scale fluctuations, has the form of the Boltzmann
weight for Yang-Mills theory in D=3 Euclidean dimensions. Our numerical results
support this conjectured behavior. We also investigate the form of the ground
state evaluated on shorter wavelength configurations.


title: Sets of Rich Lines in General Position

abstract:
  Given a set of $n$ points in $R^2$, the Szemer\'edi-Trotter theorem
establishes that the number of lines which can be incident to at least $k > 1$
of these points is $O(n^2/k^3 + n/k)$. J.\ Solymosi conjectured that if one
requires the points to be in a grid formation and the lines to be in general
position---no two parallel, no three meeting at a point---then one can get a
much tighter bound. We prove: for every $\epsilon > 0$ there exists some
$\delta > 0$ such that for sufficiently large values of $n$, every set of lines
in general position, each intersecting an $n \times n$ grid of points in at
least $n^{1-\delta}$ places, has size at most $n^\epsilon$.


title: Study of Electroweak Interactions at the Energy Frontier

abstract:
  With the discovery of the Higgs boson, the spectrum of particles in the
Standard Model (SM) is complete. It is more important than ever to perform
precision measurements and to test for deviations from SM predictions in the
electroweak sector. In this report, we investigate two themes in the arena of
precision electroweak measurements: the electroweak precision observables
(EWPOs) that test the particle content and couplings in the SM and the minimal
supersymmetric SM, and the measurements involving multiple gauge bosons in the
final state which provide unique probes of the basic tenets of electroweak
symmetry breaking. Among the important EWPOs we focus our discussion on M_W and
sin^2 theta_eff^l, and on anomalous quartic gauge couplings probed by triboson
production and vector boson scattering. We investigate the thresholds of
precision that need to be achieved in order to be sensitive to new physics. We
study the precision that can be achieved at various facilities on these
observables. We discuss the calculational tools needed to predict SM rates and
distributions in order to perform these measurements at the required precision.
This report summarizes the work of the Energy Frontier Precision Study of
Electroweak Interactions working group of the 2013 Community Summer Study
(Snowmass).


title:
First Principles Calculation of Elastic Moduli of Early-Late Transition
  Metal Alloys

abstract:
  Motivated by interest in the elastic properties of high strength amorphous
metals, we examine the elastic properties of select crystalline phases. Using
first principles methods, we calculate elastic moduli in various chemical
systems containing transition metals, specifically early (Ta,W) and late
(Co,Ni). Theoretically predicted alloy elastic properties are verified for
Ni-Ta by comparison with experimental measurements using resonant ultrasound
spectroscopy. Comparison of our computed elastic moduli with effective medium
theories shows that alloying leads to enhancement of bulk moduli relative to
averages of the pure elements, and considerable deviation of predicted and
computed shear moduli. Specifically, we find an enhancement of bulk modulus
relative to effective medium theory and propose a candidate system for high
strength, ductile amorphous alloys. Trends in the elastic properties of
chemical systems are analyzed using force constants, electronic densities of
state and Crystal Overlap Hamilton Populations. We interpret our findings in
terms of the electronic structure of the alloys.


title:
Enhanced homotopy theory for period integrals of smooth projective
  hypersurfaces

abstract:
  The goal of this paper is to reveal hidden structures on the singular
cohomology and the Griffiths period integral of a smooth projective
hypersurface in terms of BV(Batalin-Vilkovisky) algebras and homotopy Lie
theory (so called, $L_\infty$-homotopy theory).
  Let $X_G$ be a smooth projective hypersurface in the complex projective space
$\mathbf{P}^n$ defined by a homogeneous polynomial $G(\underline x)$ of degree
$d \geq 1$. Let $\mathbb{H}=H^{n-1}_{\operatorname{prim}}(X_G, \mathbb{C})$ be
the middle dimensional primitive cohomology of $X_G$. We explicitly construct a
BV algebra $\mathbf{B\!\!V}_{\! \!X}=(\mathcal{A}_X,Q_X, K_X)$ such that its
$0$-th cohomology $H^0_{K_X}(\mathcal{A}_X)$ is canonically isomorphic to
$\mathbb{H}$. We also equip $\mathbf{B\!\!V}_{\! \!X}$ with a decreasing
filtration and a bilinear pairing which realize the Hodge filtration and the
cup product polarization on $\mathbb{H}$ under the canonical isomorphism.
Moreover, we lift $C_{[\gamma]}:\mathbb{H} \to \mathbb{C}$ to a cochain map
$\mathcal{C}_\gamma:(\mathcal{A}_X, K_X) \to (\mathbb{C},0)$, where
$C_{[\gamma]}$ is the Griffiths period integral given by $\omega \mapsto
\int_\gamma \omega$ for $[\gamma]\in H_{n-1}(X_G,\mathbb{Z})$.
  We use this enhanced homotopy structure on $\mathbb{H}$ to study an extended
formal deformation of $X_G$ and the correlation of its period integrals. If
$X_G$ is in a formal family of Calabi-Yau hypersurfaces $X_{G_{\underline T}}$,
we provide an explicit formula and algorithm (based on a Gr\"obner basis) to
compute the period matrix of $X_{G_{\underline T}}$ in terms of the period
matrix of $X_G$ and an $L_\infty$-morphism $\underline \kappa$ which enhances
$C_{[\gamma]}$ and governs deformations of period matrices.


title:
Optimal pointwise estimates for derivatives of solutions to Laplace,
  Lam\'e and Stokes equations

abstract:
  Various optimal estimates for solutions of the Laplace, Lam\'e and Stokes
equations in multidimensional domains, as well as new real-part theorems for
analytic functions are obtained.


title:
On higher-order Szego theorems with a single critical point of arbitrary
  order

abstract:
  We prove the following higher-order Szego theorems: if a measure on the unit
circle has absolutely continuous part $w(\theta)$ and Verblunsky coefficients
$\alpha$ with square-summable variation, then for any positive integer $m$,
$\int (1-\cos \theta)^m \log w(\theta) d\theta$ is finite if and only if
$\alpha \in \ell^{2m+2}$.
  This is the first known equivalence result of this kind in the regime of very
slow decay, i.e. with $\ell^p$ conditions with arbitrarily large $p$. The usual
difficulty of controlling higher-order sum rules is avoided by a new test
sequence approach.


title:
Parameter Estimation: The Proper Way to Use Bayesian Posterior Processes
  with Brownian Noise

abstract:
  This paper studies a problem of Bayesian parameter estimation for a sequence
of scaled counting processes whose weak limit is a Brownian motion with an
unknown drift. The main result of the paper is that the limit of the posterior
distribution processes is, in general, not equal to the posterior distribution
process of the mentioned Brownian motion with the unknown drift. Instead, it is
equal to the posterior distribution process associated with a Brownian motion
with the same unknown drift and a different standard deviation coefficient. The
difference between the two standard deviation coefficients can be arbitrarily
large. The characterization of the limit of the posterior distribution
processes is then applied to a family of stopping time problems. We show that
the proper way to find asymptotically optimal solutions to stopping time
problems w.r.t.~the scaled counting processes is by looking at the limit of the
posterior distribution processes rather than by the naive approach of looking
at the limit of the scaled counting processes themselves. The difference
between the performances can be arbitrarily large.


title: Spin Excitations in Half-Doped Manganites

abstract:
  We investigate magnetic excitations in half-doped colossal magnetoresistance
manganites. In particular, we focus on spin excitations in the CE phase
originally proposed by Goodenough (Phys. Rev. 100, 564 (1955)). Using a
localized spin model we calculated magnons for 3D-perovskite compounds such as
La$_{1-x}$M$_x$MnO$_3$, where M=Ca,Sr,Ba, and for their 2D-laminar
counterparts. We compared them with predictions for the spin excitations
corresponding to other phases proposed. For the laminar half-doped manganite
La$_{0.5}$Sr$_{1.5}$MnO$_4$, for which magnon measurements by inelastic neutron
scattering exist, as well as an estimation of the magnetic couplings, our
calculations agree well with the experimental data.


title:
Thermophysical properties of near-Earth asteroid (341843) 2008 EV5 from
  WISE data

abstract:
  Aims. To derive the thermal inertia of 2008 EV$_5$, the baseline target for
the Marco Polo-R mission proposal, and infer information about the size of the
particles on its surface. Methods. Values of thermal inertia are obtained by
fitting an asteroid thermophysical model to NASA's Wide-field Infrared Survey
Explorer (WISE) infrared data. From the constrained thermal inertia and a model
of heat conductivity that accounts for different values of the packing fraction
(a measure of the degree of compaction of the regolith particles), grain size
is derived. Results. We obtain an effective diameter $D = 370 \pm
6\,\mathrm{m}$, geometric visible albedo $p_V = 0.13 \pm 0.05$ (assuming
$H=20.0 \pm 0.4$), and thermal inertia $\Gamma = 450 \pm 60$ J/m2/s(1/2)/K at
the 1-$\sigma$ level of significance for its retrograde spin pole solution. The
regolith particles radius is $r = 6.6^{+1.3}_{-1.3}$ mm for low degrees of
compaction, and $r = 12.5^{+2.7}_{-2.6}$ mm for the highest packing densities.


title:
Search for primordial non-Gaussianity in the quasars of SDSS-III BOSS
  DR9

abstract:
  We analyse the clustering of 22,361 quasars between redshift 2.2 < z < 2.9
observed with the Sloan Digital Sky Survey (SDSS)-III Baryon Oscillation
Spectroscopic Survey (BOSS), which are included in the ninth data release
(DR9). We fit the clustering results with a {\Lambda}CDM model to calculate the
linear bias of the quasar sample, b=3.74\pm 0.12. The measured value of bias is
consistent with the findings of White et al. (2012), where they analyse almost
the same quasar sample, although only in the range, s<40 Mpc/h. At large scales
we observe an excess or plateau in the clustering correlation function. By
fitting a model that incorporates a scale dependent additional term in the bias
introduced by primordial non-Gaussianity of the local type, we calculate the
amplitude of the deviation from the Gaussian initial conditions as 70<f_NL< 190
at the 95% confidence level. We correct the sample from systematics according
to the methods of Ross et al. (2011); Ho et al. (2012) and Ross et al.
(2011,2012b), with the f_NL measurements after the application of the two
methods being consistent with each other. Finally we use cross-correlations
across redshift slices to test the corrected sample for any remaining unknown
sources of systematics, but the results give no indication of any such further
errors. We consider as our final results on non-Gaussianity of the local type,
46<f_NL< 158 at 95% confidence, after correcting the sample with the weights
method of Ross et al. (2011, 2012b). These results are consistent with previous
tight constraints on non-Gaussianity from other LSS surveys, but are in tension
with the latest results from the CMB.


title: The First AllWISE Proper Motion Discovery: WISEA J070720.50+170532.7

abstract:
  While quality checking a new motion-aware co-addition of all 12.5 months of
WISE data, the source WISE J070720.48+170533.0 was found to have moved 0.9
arc-sec in 6 months. Backtracking this motion allowed us to identify this
source as 2MASS J07071961+1705464 and with several entries in the USNO B
catalog. An astrometric fit to these archival data gives a proper motion of
1793 +/- 2 mas/yr and a parallax of 35 +/- 42 mas. Photometry from WISE, 2MASS
and the POSS can be fit reasonably well by a blackbody with T = 3658 K and an
angular radius of 4.36E-11 radians. No clear evidence of H_2 collision-induced
absorption is seen in the near-IR. An optical spectrum shows broad deep CaH
bands at 638 and 690 nm, broad deep Na D at 598.2 nm, and weak or absent TiO,
indicating that this source is an ultra-subdwarf M star with a radial velocity
about -21 +/- 18 km/sec relative to the Sun. Given its apparent magnitude, the
distance is about 39 +/- 9 pc and the tangential velocity is probably about 330
km/sec, but a more precise parallax is needed to be certain.


title: Generation of Universal Linear Optics by Any Beamsplitter

abstract:
  In 1994, Reck et al. showed how to realize any unitary transformation on a
single photon using a product of beamsplitters and phaseshifters. Here we show
that any single beamsplitter that nontrivially mixes two modes, also densely
generates the set of unitary transformations (or orthogonal transformations, in
the real case) on the single-photon subspace with m>=3 modes. (We prove the
same result for any two-mode real optical gate, and for any two-mode optical
gate combined with a generic phaseshifter.) Experimentally, this means that one
does not need tunable beamsplitters or phaseshifters for universality: any
nontrivial beamsplitter is universal for linear optics. Theoretically, it means
that one cannot produce "intermediate" models of linear optical computation
(analogous to the Clifford group for qubits) by restricting the allowed
beamsplitters and phaseshifters: there is a dichotomy; one either gets a
trivial set or else a universal set. No similar classification theorem for
gates acting on qubits is currently known. We leave open the problem of
classifying optical gates that act on three or more modes.


title: Two Dimensional Array Imaging with Beam Steered Data

abstract:
  This paper discusses different approaches used for millimeter wave imaging of
two-dimensional objects. Imaging of a two dimensional object requires reflected
wave data to be collected across two distinct dimensions. In this paper, we
propose a reconstruction method that uses narrowband waveforms along with two
dimensional beam steering. The beam is steered in azimuthal and elevation
direction, which forms the two distinct dimensions required for the
reconstruction. The Reconstruction technique uses inverse Fourier transform
along with amplitude and phase correction factors. In addition, this
reconstruction technique does not require interpolation of the data in either
wavenumber or spatial domain. Use of the two dimensional beam steering offers
better performance in the presence of noise compared with the existing methods,
such as switched array imaging system. Effects of RF impairments such as
quantization of the phase of beam steering weights and timing jitter which add
to phase noise, are analyzed.


title:
Characterization of PMMA--3-octanone binary by turbidity and light
  scattering measurements

abstract:
  We measure the coexistence curve and the critical point properties of a
binary mixture composed by polymethylmethacrylate (PMMA) at $M_w = 55900$ g/mol
with 3- octanone. This binary mixture which has a demixing transition with an
upper critical solution temperature $T_c$ has indeed interesting properties
which may be useful for several application : a) its correlation length is
larger than that of a liquid-liquid binary mixture, b) it is less viscous than
a polymer blend; c) 3- octanone has an evaporation rate much smaller than other
solvents. The mixture is first characterized by turbidity, to get the demixing
temperature for different volumic fraction of PMMA. The coordinates of the
critical point are obtained: $\phi_c = 12.8\pm0.2$ % and $T_c = 306.5\pm0.1$ K.
The correlation length $\xi$ near the critical point is then measured in a
solution with a 12.8% volumic fraction of PMMA using static light scattering.
Using the fact that PMMA-octanone mixture has scaling exponents compatible with
Ising 3D, we determine more precisely the critical temperature $T_c =
306.58\pm0.04$ K and we find that $\xi \simeq \xi_0 [(T-T_c)/{T_c}]^{-0.63}$
with $\xi_0 = 0.97\pm 0.02$ nm. The discrepancy between this value and that
extrapolated from other measurements based on turbidity is discussed.


title: Cubic congruences and sums involving $\binom{3k}k$

abstract:
  Let $p$ be a prime greater than $3$ and let $a$ be a rational p-adic integer.
In this paper we try to determine $\sum_{k=1}^{[p/3]}\binom{3k}ka^k\pmod p$,
and real the connection between cubic congruences and the sum
$\sum_{k=1}^{[p/3]}\binom{3k}ka^k$, where $[x]$ is the greatest integer not
exceeding $x$. Suppose that $a_1,a_2,a_3$ are rational p-adic integers,
$P=-2a_1^3+9a_1a_2-27a_3$, $Q=(a_1^2-3a_2)^3$ and
$PQ(P^2-Q)(P^2-3Q)(P^2-4Q)\not\equiv 0\pmod p$. In this paper we show that the
number of solutions of the congruence $x^3+a_1x^2+a_2x+a_3\equiv 0\pmod p$
depends only on $\sum_{k=1}^{[p/3]}\binom{3k}k(\frac{4Q-P^2}{27Q})^k\pmod p$.
  Let $q$ be a prime of the form $3k+1$ and so $4q=L^2+27M^2$ with $L,M\in\Bbb
Z$. When $p\not=q$ and $p\nmid L$, we establish congruences for
$\sum_{k=1}^{[p/3]}\binom{3k}k(\frac{M^2}q)^k$ and
$\sum_{k=1}^{[p/3]}\binom{3k}k(\frac{L^2}{27q})^k$ modulo p. As a consequence,
we show that $x^3-qx-qM\equiv 0\pmod p$ has three solutions if and only if $p$
is a cubic residue of $q$.


title:
Theory of excitations of dipolar Bose-Einstein condensate at finite
  temperature

abstract:
  We present a systematic study of dilute three-dimensional dipolar Bose gas
employing a finite temperature perturbation theory (beyond the mean field). We
analyze in particular the behavior of the anomalous density, we find that this
quantity has a finite value in the limit of weak interactions at both zero and
finite temperatures. We show that the presence of the dipole-dipole interaction
(DDI) enhances fluctuations, the second order correlation function and
thermodynamic quantities such as the chemical potential, the ground state
energy, the compressibility and the superfluid fraction. We identify the
validity criterion of the small parameter of the theory for Bose-condensed
dipolar gases.


title: Divided difference operators in equivariant $KK$-theory

abstract:
  Let $G$ be a compact connected Lie group with a maximal torus $T$. Let $A$,
$B$ be $G$-$\mathrm{C}^\ast$-algebras. We define certain divided difference
operators on Kasparov's $T$-equivariant $KK$-group $KK_T(A,B)$ and show that
$KK_G(A,B)$ is a direct summand of $KK_T(A,B)$. More precisely, a
$T$-equivariant $KK$-class is $G$-equivariant if and only if it is annihilated
by an ideal of divided difference operators. This result is a generalization of
work done by Atiyah, Harada, Landweber and Sjamaar.


title:
A new determination of $\alpha_S$ from Renormalization Group Optimized
  Perturbation

abstract:
  A new version of the so-called optimized perturbation (OPT), implementing
consistently renormalization group properties, is used to calculate the
nonperturbative ratio $F_\pi/\overline\Lambda$ of the pion decay constant and
the basic QCD scale in the $\overline{MS}$ scheme. Using the experimental
$F_\pi$ input value it provides a new determination of $\overline\Lambda$ for
$n_f=2$ and $n_f=3$, and of the QCD coupling constant $\overline\alpha_S $ at
various scales once combined with a standard perturbative evolution. The
stability and empirical convergence properties of the RGOPT modified series is
demonstrated up to the third order. We examine the difference sources of
theoretical uncertainties and obtain $\overline\alpha_S (m_Z) =0.1174
^{+.0010}_{-.0005} \pm .001 \pm .0005_{evol}$, where the first errors are
estimates of the intrinsic theoretical uncertainties of our method, and the
second errors come from present uncertainties in $F_\pi/F_0$, where $F_0$ is
$F_\pi$ in the exact chiral $SU(3)$ limit.


title: Universal Properties of the Langevin Diffusion Coefficients

abstract:
  We show that in generic isotropic holographic theories the longitudinal
Langevin diffusion coefficient along the string motion is larger compared to
that of the transverse direction. We argue that this is a universal relation
and we derive the generic conditions in order to be satisfied. A way to violate
the relation is to consider anisotropic gauge/gravity dualities. We give an
explicit example of this violation where the noise along the transverse
direction is larger than the noise occurring along the quark motion. Moreover,
we derive the effective world-sheet temperature for any generic theory and then
the conditions for negative excess noise. We argue that isotropic theories can
not have negative excess noise and we additionally remark that these conditions
are difficult to get satisfied, indicating positivity of the excess noise, even
in a large class of anisotropic holographic theories.


title: On the descent polynomial of signed multipermutations

abstract:
  Motivated by a conjecture of Savage and Visontai about the equidistribution
of the descent statistic on signed permutations of the multiset
$\{1,1,2,2,\ldots,n,n\}$ and the ascent statistic on
$(1,4,3,8,\ldots,2n-1,4n)$-inversion sequences, we investigate the descent
polynomial of the signed permutations of a general multiset. We obtain a
factorial generating function formula for a $q$-analog of these descent
polynomials and apply it to show that they have only real roots. Two different
proofs of the conjecture of Savage and Visontai are provided.


title: An effective proof of the hyperelliptic Shafarevich conjecture

abstract:
  Let $C$ be a hyperelliptic curve of genus $g\geq 1$ over a number field $K$
with good reduction outside a finite set of places $S$ of $K$. We prove that
$C$ has a Weierstrass model over the ring of integers of $K$ with height
effectively bounded only in terms of $g$, $S$ and $K$. In particular, we obtain
that for any given number field $K$, finite set of places $S$ of $K$ and
integer $g\geq 1$ one can in principle determine the set of $K$-isomorphism
classes of hyperelliptic curves over $K$ of genus $g$ with good reduction
outside $S$.


title:
Quantization ambiguities and bounds on geometric scalars in anisotropic
  loop quantum cosmology

abstract:
  We study quantization ambiguities in loop quantum cosmology that arise for
space-times with non-zero spatial curvature and anisotropies. Motivated by
lessons from different possible loop quantizations of the closed
Friedmann-Lemaitre-Robertson-Walker cosmology, we find that using open
holonomies of the extrinsic curvature, which due to gauge-fixing can be treated
as a connection, leads to the same quantum geometry effects that are found in
spatially flat cosmologies. More specifically, in contrast to the quantization
based on open holonomies of the Ashtekar-Barbero connection, the expansion and
shear scalars in the effective theories of the Bianchi type II and Bianchi type
IX models have upper bounds, and these are in exact agreement with the bounds
found in the effective theories of the Friedmann-Lemaitre-Robertson-Walker and
Bianchi type I models in loop quantum cosmology. We also comment on some
ambiguities present in the definition of inverse triad operators and their
role.


title:
Examination of the tradeoff between intrinsic and extrinsic properties
  in the optimization of a modern internal tin Nb3Sn conductor

abstract:
  In modern Nb3Sn wires there is a fundamental compromise to be made between
optimizing the intrinsic properties associated with the superfluid density in
the A15 phase (e.g. Tc, Hc, Hc2, all of which are composition dependent),
maximizing the quantity of A15 that can be formed from a given mixture of Nb,
Sn and Cu, minimizing the A15 composition gradients within each sub-element,
while at the same time generating a high vortex pinning critical current
density, Jc, by maximizing the grain boundary density with the additional
constraint of maintaining the RRR of the Cu stabilizer above 100. Here we study
these factors in a Ta-alloyed Restacked-Rod-Process (RRP) wire with ~70 microns
diameter sub-elements. Consistent with many earlier studies, maximum non-Cu
Jc(12T,4.2K) requires preventing A15 grain growth, rather than by optimizing
the superfluid density. In wires optimized for 12T, 4.2K performance, about 60%
of the non-Cu cross-section is A15, 35% residual Cu and Sn core, and only 5% a
residual Nb7.5wt.%Ta diffusion barrier. The specific heat and chemical analyses
show that in this 60% A15 fraction there is a wide range of Tc and chemical
composition that does diminish for higher heat treatment temperatures, which,
however, are impractical because of the strong RRR degradation that occurs when
only about 2% of the A15 reaction front breaches the diffusion barrier. As this
kind of Nb3Sn conductor design is being developed for sub-elements 1/2 the
present size, it is clear that better barriers are essential to allowing higher
temperature reactions with better intrinsic A15 properties. We present here
multiple and detailed intrinsic and extrinsic evaluations because we believe
that only such broad and quantitative descriptions are capable of accurately
tracking the limitations of individual conductor designs where optimization
will always be a compromise between inherently conflicting goals


title: Temperature dependence of crystal field excitations in CuO

abstract:
  We report a study on the temperature dependence of the charge-neutral crystal
field (dd) excitations in cupric oxide, using nonresonant inelastic x-ray
scattering (IXS) spectroscopy. Thanks to a very high energy resolution (60
meV), we observe thermal effects on the dd excitation spectrum fine structure
between temperatures of 10-320 K. With an increasing temperature, the spectra
broaden considerably. We assign the temperature dependence of the dd
excitations to the relatively large electron-phonon coupling.


title: Zermelo Navigation and a Speed Limit to Quantum Information Processing

abstract:
  We use a specific geometric method to determine speed limits to the
implementation of quantum gates in controlled quantum systems that have a
specific class of constrained control functions. We achieve this by applying a
recent theorem of Shen, which provides a connection between time optimal
navigation on Riemannian manifolds and the geodesics of a certain Finsler
metric of Randers type. We use the lengths of these geodesics to derive the
optimal implementation times (under the assumption of constant control fields)
for an arbitrary quantum operation (on a finite dimensional Hilbert space), and
explicitly calculate the result for the case of a controlled single spin system
in a magnetic field, and a swap gate in a Heisenberg spin chain.


title:
Spectral measurement of electron antineutrino oscillation amplitude and
  frequency at Daya Bay

abstract:
  A measurement of the energy dependence of antineutrino disappearance at the
Daya Bay Reactor Neutrino Experiment is reported. Electron antineutrinos
($\overline{\nu}_{e}$) from six $2.9$ GW$_{\rm th}$ reactors were detected with
six detectors deployed in two near (effective baselines 512 m and 561 m) and
one far (1579 m) underground experimental halls. Using 217 days of data, 41589
(203809 and 92912) antineutrino candidates were detected in the far hall (near
halls). An improved measurement of the oscillation amplitude
$\sin^{2}2\theta_{13} = 0.090^{+0.008}_{-0.009} $ and the first direct
measurement of the $\overline{\nu}_{e}$ mass-squared difference $|\Delta
m^{2}_{ee}|= (2.59_{-0.20}^{+0.19}) \times 10^{-3}\ {\rm eV}^2 $ is obtained
using the observed $\overline{\nu}_{e}$ rates and energy spectra in a
three-neutrino framework.
  This value of $|\Delta m^{2}_{ee}|$ is consistent with $|\Delta
m^{2}_{\mu\mu}|$ measured by muon neutrino disappearance, supporting the
three-flavor oscillation model.


title: Etching of Cr tips for scanning tunneling microscopy of cleavable oxides

abstract:
  We report a detailed three-step roadmap for the fabrication and
characterization of bulk Cr tips for spin-polarized scanning tunneling
microscopy. Our strategy uniquely circumvents the need for ultra-high vacuum
preparation of clean surfaces or films. First, we demonstrate the role of
$ex$-$situ$ electrochemical etch parameters on Cr tip apex geometry, using
scanning electron micrographs of over 70 etched tips. Second, we describe the
suitability of the $in$-$situ$ cleaved surface of the layered antiferromagnet
La$_{1.4}$Sr$_{1.6}$Mn$_2$O$_7$ to evaluate the spin characteristics of the Cr
tip, replacing the UHV-prepared test samples that have been used in prior
studies. Third, we outline a statistical algorithm that can effectively
delineate closely-spaced or irregular cleaved step edges, to maximize the
accuracy of step height and spin-polarization measurements.


title: A note on graded hypersurface singularities

abstract:
  For a weighted quasihomogeneous two dimensional hypersurface singularity, we
define a smoothing with unipotent monodromy and an isolated graded normal
singularity. We study the natural weighted blow up of both the smoothing and
the surface. In particular, we describe our construction for the
quasihomogeneous singularities of type I, the 14 unimodal exceptional
singularities and we relate it to their stable replacement.


title:
Hunting for treasures among the Fermi unassociated sources: a
  multi-wavelength approach

abstract:
  The Fermi Gamma-ray Space Telescope has been detecting a wealth of sources
where the multi-wavelength counterpart is either inconclusive or missing
altogether. We present a combination of factors that can be used to identify
multi-wavelength counterparts to these Fermi unassociated sources. This
approach was used to select and investigate seven bright, high-latitude
unassociated sources with radio, UV, X-ray and gamma-ray observations. As a
result, four of these sources are candidates to be active galactic nuclei
(AGN), and one to be a pulsar, while two do not fit easily into these known
categories of sources. The latter pair of extra-ordinary sources might reveal a
new category subclass or a new type of gamma-ray emitters. These results
altogether demonstrate the power of a multi-wavelength approach to illuminate
the nature of unassociated Fermi sources.


title: Fast 3D Salient Region Detection in Medical Images using GPUs

abstract:
  Automated detection of visually salient regions is an active area of research
in computer vision. Salient regions can serve as inputs for object detectors as
well as inputs for region based registration algorithms. In this paper we
consider the problem of speeding up computationally intensive bottom-up salient
region detection in 3D medical volumes.The method uses the Kadir Brady
formulation of saliency. We show that in the vicinity of a salient region,
entropy is a monotonically increasing function of the degree of overlap of a
candidate window with the salient region. This allows us to initialize a sparse
seed-point grid as the set of tentative salient region centers and iteratively
converge to the local entropy maxima, thereby reducing the computation
complexity compared to the Kadir Brady approach of performing this computation
at every point in the image. We propose two different approaches for achieving
this. The first approach involves evaluating entropy in the four quadrants
around the seed point and iteratively moving in the direction that increases
entropy. The second approach we propose makes use of mean shift tracking
framework to affect entropy maximizing moves. Specifically, we propose the use
of uniform pmf as the target distribution to seek high entropy regions. We
demonstrate the use of our algorithm on medical volumes for left ventricle
detection in PET images and tumor localization in brain MR sequences.


title: Multiband responses in high-Tc cuprate superconductors

abstract:
  We report on the interplay of localized and extended degrees of freedom in
the metallic state of high-temperature superconductors in a multiband setting.
Various ways in which the bare magnetic response may become incommensurate are
measured against both phenomenological and theoretical requirements. In
particular, the pseudogap temperature is typically much higher than the
incommensurability temperature. When microscopic strong-coupling effects with
real-time dynamics between copper and oxygen sites are included, they tend to
restore commensurability. Quantum transport equations for low-dimensional
multiband electronic systems are used to explain the linear doping dependence
of the dc conductivity and the doping and temperature dependence of the Hall
number in the underdoped LSCO compounds. Coulomb effects of dopands are
inferred from the doping evolution of the Hartree-Fock model parameters.


title:
Dispersal-induced destabilization of metapopulations and oscillatory
  Turing patterns in ecological networks

abstract:
  As proposed by Alan Turing in 1952 as a ubiquitous mechanism for
nonequilibrium pattern formation, diffusional effects may destabilize uniform
distributions of reacting chemical species and lead to both spatially and
temporally heterogeneous patterns. While stationary Turing patterns are broadly
known, the oscillatory instability, leading to traveling waves in continuous
media and also called the wave bifurcation, is rare for chemical systems. Here,
we extend the analysis by Turing to general networks and apply it to ecological
metapopulations of biological species with dispersal connections between
habitats. Remarkably, the oscillatory Turing instability does not lead to wave
patterns in networks, but to spontaneous development of heterogeneous
oscillations and possible extinction of some species, even though they are
absent for isolated populations. Furthermore, our theoretical analysis reveals
that this instability is more common in ecological metapopulations than in
chemical reactions. Indeed, we find the instabilities for all possible food
webs with three predator or prey species, under various assumptions about the
mobility of individual species and nonlinear interactions between them.
Therefore, we suggest that the oscillatory Turing instability is generic and
must play a fundamental role in metapopulation dynamics, providing a common
mechanism for dispersal-induced destabilization of ecosystems.


title: Fano resonances in antennas: General control over radiation patterns

abstract:
  The concepts of many optical devices are based on the fundamental physical
phenomena such as resonances. One of the commonly used devices is an
electromagnetic antenna that converts localized energy into freely propagating
radiation and vise versa, offering unique capabilities for controlling
electromagnetic radiation. Here we propose a concept for controlling the
intensity and directionality of electromagnetic wave scattering in
radio-frequency and optical antennas based on the physics of Fano resonances.
We develop an analytical theory of spatial Fano resonances in antennas that
describes switching of the radiation pattern between the forward and backward
directions, and confirm our theory with both numerical calculations and
microwave experiments. Our approach bridges the concepts of conventional radio
antennas and photonic nanoantennas, and it provides a paradigm for the design
of wireless optical devices with various functionalities and architectures.


title: Active Learning of Linear Embeddings for Gaussian Processes

abstract:
  We propose an active learning method for discovering low-dimensional
structure in high-dimensional Gaussian process (GP) tasks. Such problems are
increasingly frequent and important, but have hitherto presented severe
practical difficulties. We further introduce a novel technique for
approximately marginalizing GP hyperparameters, yielding marginal predictions
robust to hyperparameter mis-specification. Our method offers an efficient
means of performing GP regression, quadrature, or Bayesian optimization in
high-dimensional spaces.


title: Design principles governing the motility of myosin V

abstract:
  The molecular motor myosin V exhibits a wide repertoire of pathways during
the stepping process, which is intimately connected to its biological function.
The best understood of these is hand-over-hand stepping by a swinging lever arm
movement toward the plus-end of actin filaments, essential to its role as a
cellular transporter. However, single-molecule experiments have also shown that
the motor "foot stomps", with one hand detaching and rebinding to the same
site, and backsteps under sufficient load. Explaining the complete taxonomy of
myosin V's load-dependent stepping pathways, and the extent to which these are
constrained by motor structure and mechanochemistry, are still open questions.
Starting from a polymer model, we develop an analytical theory to understand
the minimal physical properties that govern motor dynamics. In particular, we
solve the first-passage problem of the head reaching the target binding site,
investigating the competing effects of load pulling back at the motor, strain
in the leading head that biases the diffusion in the direction of the target,
and the possibility of preferential binding to the forward site due to the
recovery stroke. The theory reproduces a variety of experimental data,
including the power stroke and slow diffusive search regimes in the mean
trajectory of the detached head, and the force dependence of the
forward-to-backward step ratio, run length, and velocity. The analytical
approach yields a formula for the stall force, identifying the relative
contributions of the chemical cycle rates and mechanical features like the
bending rigidities of the lever arms. Most importantly, by fully exploring the
design space of the motor, we predict that myosin V is a robust motor whose
dynamical behavior is not compromised by reasonable perturbations to the
reaction cycle, and changes in the architecture of the lever arm.


title: Disk Destruction and (Re)-Creation in the Magellanic Clouds

abstract:
  Unlike most satellite galaxies in the Local Group that have long lost their
gaseous disks, the Magellanic Clouds are gas-rich dwarf galaxies most-likely on
their first pericentric passage allowing us to study disk evolution on the
smallest scales. The Magellanic Clouds show both disk destruction and
(re)-creation. The Large Magellanic Cloud has a very extended stellar disk
reaching to at least 15 kpc (10 radial scalelengths) while its gaseous disk is
truncated at ~5 kpc mainly due to its interaction with the hot gaseous halo of
the Milky Way. The stellar disk of the Small Magellanic Cloud, on the other
hand, has essentially been destroyed. The old stellar populations show no sign
of rotation (being pressure supported) and have an irregular and elongated
shape. The SMC has been severely disturbed by its close encounters with the LMC
(the most recent only 200 Myr ago) which have also stripped out large
quantities of gas creating much of the Magellanic Stream and the Magellanic
Bridge. Amazingly, the SMC has an intact, rotating HI disk indicating that
either the inner HI was preserved from destruction, or, more likely, that the
HI disk reformed quickly after the last close encounter with the LMC.


title: Parametrizing and constraining scalar corrections to general relativity

abstract:
  We parametrize a large class of corrections to general relativity which
include a long-ranged gravitational scalar field as a dynamical degree of
freedom in two ways: parametrizing the structure of the correction to the
action, and parametrizing the scalar hair (multipole structure) that compact
objects and black holes attain. The presence of this scalar hair violates the
no-hair theorems present in general relativity, which leads to several
important effects. The effects we consider are (i) the interaction between an
isolated body and an external scalar field, (ii) the scalar multipole-multipole
interaction between two bodies in a compact binary, (iii) the additional
pericenter precession of a binary, (iv) the scalar radiation from a binary, and
(v) the modification to the gravitational wave phase from a binary. We apply
this framework to example theories including Einstein-dilaton-Gauss-Bonnet
gravity and dynamical Chern-Simons gravity, and estimate the size of the
effects. Finally, we estimate the bounds that can be placed on parameters of
the theories from the precession of pulsar binaries and from gravitational
waves.


title:
Weak lensing analysis of SZ-selected clusters of galaxies from the SPT
  and Planck surveys

abstract:
  We present the weak lensing analysis of the Wide-Field Imager SZ Cluster of
galaxy (WISCy) sample, a set of 12 clusters of galaxies selected for their
Sunyaev-Zel'dovich (SZ) effect. After developing new and improved methods for
background selection and determination of geometric lensing scaling factors
from absolute multi-band photometry in cluster fields, we compare the weak
lensing mass estimate with public X-ray and SZ data. We find consistency with
hydrostatic X-ray masses with no significant bias, no mass dependent bias and
less than 20% intrinsic scatter and constrain fgas,500c=0.128+0.029-0.023. We
independently calibrate the South Pole Telescope significance-mass relation and
find consistency with previous results. The comparison of weak lensing mass and
Planck Compton parameters, whether extracted self-consistently with a
mass-observable relation (MOR) or using X-ray prior information on cluster
size, shows significant discrepancies. The deviations from the MOR strongly
correlate with cluster mass and redshift. This could be explained either by a
significantly shallower than expected slope of Compton decrement versus mass
and a corresponding problem in the previous X-ray based mass calibration, or a
size or redshift dependent bias in SZ signal extraction.


title: Two timescale dispersal of magnetized protoplanetary disks

abstract:
  Protoplanetary disks are likely to be threaded by a weak net flux of vertical
magnetic field that is a remnant of the much larger fluxes present in molecular
cloud cores. If this flux is approximately conserved its dynamical importance
will increase as mass is accreted, initially by stimulating magnetorotational
disk turbulence and subsequently by enabling wind angular momentum loss. We use
fits to numerical simulations of ambipolar dominated disk turbulence to
construct simplified one dimensional evolution models for weakly magnetized
protoplanetary disks. We show that the late onset of significant angular
momentum loss in a wind can give rise to "two timescale" disk evolution in
which a long phase of viscous evolution precedes rapid dispersal as the wind
becomes dominant. The wide dispersion in disk lifetimes could therefore be due
to varying initial levels of net flux. Magnetohydrodynamic (MHD) wind triggered
dispersal differs from photoevaporative dispersal in predicting mass loss from
small (less that 1 AU) scales, where thermal winds are suppressed. Our specific
models are based on a limited set of simulations that remain uncertain, but
qualitatively similar evolution appears likely if mass is lost from disks more
quickly than flux, and if MHD winds become important as the plasma beta
decreases.


title: ELVIS: Exploring the Local Volume in Simulations

abstract:
  We introduce a set of high-resolution dissipationless simulations that model
the Local Group (LG) in a cosmological context: Exploring the Local Volume in
Simulations (ELVIS). The suite contains 48 Galaxy-size halos, each within
high-resolution volumes that span 2-5 Mpc in size, and each resolving thousands
of systems with masses below the atomic cooling limit. Half of the ELVIS galaxy
halos are in paired configurations similar to the Milky Way (MW) and M31; the
other half are isolated, mass-matched analogs. We find no difference in the
abundance or kinematics of substructure within the virial radii of isolated
versus paired hosts. On Mpc scales, however, LG-like pairs average almost twice
as many companions and the velocity field is kinematically hotter and more
complex. We present a refined abundance matching relation between stellar mass
and halo mass that reproduces the observed satellite stellar mass functions of
the MW and M31 down to the regime where incompleteness is an issue, $M_\star
\sim 5\times 10^5 \, M_\odot$. Within a larger region spanning approximately 3
Mpc, the same relation predicts that there should be $\sim$ 1000 galaxies with
$M_\star > 10^{3}\,M_\odot$ awaiting discovery. We show that up to 50% of halos
within 1 Mpc of the MW or M31 could be systems that have previously been within
the virial radius of either giant. By associating never-accreted halos with
gas-rich dwarfs, we show that there are plausibly 50 undiscovered dwarf
galaxies with HI masses $> 10^5\,M_\odot$ within the Local Volume. The radial
velocity distribution of these predicted gas-rich dwarfs can be used to inform
follow-up searches based on ultra-compact high-velocity clouds found in the
ALFALFA survey.


title:
The Dark Side of Galaxy Color: evidence from new SDSS measurements of
  galaxy clustering and lensing

abstract:
  The age matching model has recently been shown to predict correctly the
luminosity L and g-r color of galaxies residing within dark matter halos. The
central tenet of the model is intuitive: older halos tend to host galaxies with
older stellar populations. In this paper, we demonstrate that age matching also
correctly predicts the g-r color trends exhibited in a wide variety of
statistics of the galaxy distribution for stellar mass M* threshold samples. In
particular, we present new measurements of the galaxy two-point correlation
function and the galaxy-galaxy lensing signal as a function of M* and g-r color
from the Sloan Digital Sky Survey, and show that age matching exhibits
remarkable agreement with these and other statistics of low-redshift galaxies.
In so doing, we also demonstrate good agreement between the galaxy-galaxy
lensing observed by SDSS and the signal predicted by abundance matching, a new
success of this model. We describe how age matching is a specific example of a
larger class of Conditional Abundance Matching models (CAM), a theoretical
framework we introduce here for the first time. CAM provides a general
formalism to study correlations at fixed mass between any galaxy property and
any halo property. The striking success of our simple implementation of CAM
provides compelling evidence that this technique has the potential to describe
the same set of data as alternative models, but with a dramatic reduction in
the required number of parameters. CAM achieves this reduction by exploiting
the capability of contemporary N-body simulations to determine dark matter halo
properties other than mass alone, which distinguishes our model from
conventional approaches to the galaxy-halo connection.


title: Galaxy Formation with local photoionisation feedback I. Methods

abstract:
  We present a first study of the effect of local photoionising radiation on
gas cooling in smoothed particle hydrodynamics simulations of galaxy formation.
We explore the combined effect of ionising radiation from young and old stellar
populations. The method computes the effect of multiple radiative sources using
the same tree algorithm used for gravity, so it is computationally efficient
and well resolved. The method foregoes calculating absorption and scattering in
favour of a constant escape fraction for young stars to keep the calculation
efficient enough to simulate the entire evolution of a galaxy in a cosmological
context to the present day. This allows us to quantify the effect of the local
photoionisation feedback through the whole history of a galaxy`s formation. The
simulation of a Milky Way like galaxy using the local photoionisation model
forms ~ 40 % less stars than a simulation that only includes a standard uniform
background UV field. The local photoionisation model decreases star formation
by increasing the cooling time of the gas in the halo and increasing the
equilibrium temperature of dense gas in the disc. Coupling the local radiation
field to gas cooling from the halo provides a preventive feedback mechanism
which keeps the central disc light and produces slowly rising rotation curves
without resorting to extreme feedback mechanisms. These preliminary results
indicate that the effect of local photoionising sources is significant and
should not be ignored in models of galaxy formation.


title: Simulating Quantum Circuits with Sparse Output Distributions

abstract:
  We show that several quantum circuit families can be simulated efficiently
classically if it is promised that their output distribution is approximately
sparse i.e. the distribution is close to one where only a polynomially small, a
priori unknown subset of the measurement probabilities are nonzero. Classical
simulations are thereby obtained for quantum circuits which---without the
additional sparsity promise---are considered hard to simulate. Our results
apply in particular to a family of Fourier sampling circuits (which have
structural similarities to Shor's factoring algorithm) but also to several
other circuit families, such as IQP circuits. Our results provide examples of
quantum circuits that cannot achieve exponential speed-ups due to the presence
of too much destructive interference i.e. too many cancelations of amplitudes.
The crux of our classical simulation is an efficient algorithm for
approximating the significant Fourier coefficients of a class of states called
computationally tractable states. The latter result may have applications
beyond the scope of this work. In the proof we employ and extend sparse
approximation techniques, in particular the Kushilevitz-Mansour algorithm, in
combination with probabilistic simulation methods for quantum circuits.


title:
Measuring the Kondo Cloud by Current Cross Correlations in Helical
  Liquids

abstract:
  The Kondo cloud, represented by the correlations between the magnetic moment
and the spin density in the leads of a Kondo setup, is until now eluding its
observation. We exploit the unique coupling of spin and direction of motion of
the recently discovered helical liquids in a setup with two leads to establish
a proportionality between the Kondo cloud and the time resolved current cross
correlations. This relation holds around a specific choice of model parameters.
Thereby, we provide a new and direct way to detect the Kondo cloud.


title: Contribution of bouncing gravitons to the energy-momentum tensor

abstract:
  In a model of 3-brane with matter embedded in 5D space-time conditions for
gravitons emitted from the brane to the bulk to return back to the brane are
found. A method to calculate contribution to the energy-momentum tensor from
multiple bouncing gravitons is developed. Contribution to the energy momentum
tensor from gravitons of the first bounce is calculated. The result is much
smaller than those obtained previously.


title:
Constraints on light mediators: confronting dark matter searches with B
  physics

abstract:
  Light scalars appear in many well-motivated extensions of the Standard Model
including supersymmetric models with additional gauge singlets. Such scalars
could mediate the interactions between dark matter and nuclei, giving rise to
the tentative signals observed by several dark matter direct detection
experiments including CDMS-Si. In this letter, we derive strong new limits on
light scalar mediators by using the LHCb, Belle and BaBar searches for rare
$\Upsilon$ and B decays. These limits rule out significant parts of the
parameter space favored by CDMS-Si. Nevertheless, as current searches are not
optimized for investigating weakly coupled light scalars, a further increase in
experimental sensitivity could be achieved by relaxing requirements in the
event selection.


title:
Romantic Partnerships and the Dispersion of Social Ties: A Network
  Analysis of Relationship Status on Facebook

abstract:
  A crucial task in the analysis of on-line social-networking systems is to
identify important people --- those linked by strong social ties --- within an
individual's network neighborhood. Here we investigate this question for a
particular category of strong ties, those involving spouses or romantic
partners. We organize our analysis around a basic question: given all the
connections among a person's friends, can you recognize his or her romantic
partner from the network structure alone? Using data from a large sample of
Facebook users, we find that this task can be accomplished with high accuracy,
but doing so requires the development of a new measure of tie strength that we
term `dispersion' --- the extent to which two people's mutual friends are not
themselves well-connected. The results offer methods for identifying types of
structurally significant people in on-line applications, and suggest a
potential expansion of existing theories of tie strength.


title:
Spectroscopic Confirmation of the Rich z=1.80 Galaxy Cluster JKCS 041
  Using the WFC3 Grism: Environmental Trends in the Ages and Structure of
  Quiescent Galaxies

abstract:
  We present Hubble Space Telescope imaging and grism spectroscopy in the field
of the distant galaxy cluster JKCS 041 using the Wide Field Camera 3. We
confirm that JKCS 041 is a rich cluster and derive a redshift z=1.80 via the
spectroscopic identification of 19 member galaxies, of which 15 are quiescent.
These are centered upon diffuse X-ray emission seen by the Chandra observatory.
As JKCS 041 is the most distant known cluster with such a large,
spectroscopically confirmed quiescent population, it provides a unique
opportunity to study the effect of the environment on galaxy properties at
early epochs. We construct high-quality composite spectra of the quiescent
cluster members that reveal prominent Balmer and metallic absorption lines.
Using these, we measure the mean stellar ages in two bins of stellar mass. The
quiescent cluster members' ages agree remarkably closely with that inferred by
Whitaker et al. for similarly selected samples in the field, supporting the
idea that the cluster environment is more efficient at truncating star
formation while not having a strong effect on the mean epoch of quenching. We
find some evidence (90% confidence) for a lower fraction of disk-like quiescent
systems in JKCS 041 compared to a sample of coeval field galaxies drawn from
the CANDELS survey. Taking this into account, we do not detect a significant
difference between the mass-radius relations of the quiescent JKCS 041 members
and our z~1.8 field sample. Finally, we demonstrate how differences in the
morphological mixture of quenched systems can complicate measures of the
environmental dependence of size growth.


title:
Infinite Randomness Expansion and Amplification with a Constant Number
  of Devices

abstract:
  We present a device-independent randomness expansion protocol, involving only
a constant number of non-signaling quantum devices, that achieves
\emph{infinite expansion}: starting with $m$ bits of uniform private
randomness, the protocol can produce an unbounded amount of certified
randomness that is $\exp(-\Omega(m^{1/3}))$-close to uniform and secure against
a quantum adversary. The only parameters which depend on the size of the input
are the soundness of the protocol and the security of the output (both are
inverse exponential in $m$). This settles a long-standing open problem in the
area of randomness expansion and device-independence.
  The analysis of our protocols involves overcoming fundamental challenges in
the study of \emph{adaptive} device-independent protocols. Our primary
technical contribution is the design and analysis of device-independent
protocols which are \emph{Input Secure}; that is, their output is guaranteed to
be secure against a quantum eavesdropper, \emph{even if the input randomness
was generated by that same eavesdropper}!
  The notion of Input Security may be of independent interest to other areas
such as device-independent quantum key distribution.


title: Anisotropic q-Gaussian velocity distributions in LambdaCDM halos

abstract:
  The velocity distribution function (VDF) of dark matter (DM) halos in
$\Lambda$CDM dissipationless cosmological simulations, which must be
non-separable in its radial and tangential components, is still poorly known.
We present the first single-parameter, non-separable, anisotropic model for the
VDF in $\Lambda$CDM halos, built from an isotropic $q$-Gaussian (Tsallis) VDF
of the isotropic set of dimensionless spherical velocity components (after
subtraction of streaming motions), normalized by the respective velocity
dispersions. We test our VDF on 90 cluster-mass halos of a dissipationless
cosmological simulation.
  Beyond the virial radius, $r_{\rm vir}$, our model VDF adequately reproduces
that measured in the simulated halos, but no $q$-Gaussian model can adequately
represent the VDF within $r_{\rm vir}$, as the speed distribution function is
then flatter-topped than any $q$-Gaussian can allow. Nevertheless, our VDF fits
significantly better the simulations than the commonly used Maxwellian
(Gaussian) distribution, at virtually all radii within $5\,r_{\rm vir}$. Within
0.4 (1) $r_{\rm vir}$, the non-Gaussianity index $q$ is (roughly) linearly
related to the slope of the density profile and also to the velocity anisotropy
profile. We provide a parametrization of the modulation of $q$ with radius for
both the median fits and the fit of the stacked halo. At radii of a few percent
of $r_{\rm vir}$, corresponding to the Solar position in the Milky Way, our
best-fit VDF, although fitting better the simulations than the Gaussian one,
overproduces significantly the fraction of high velocity objects, indicating
that one should not blindly use these $q$-Gaussian fits to make predictions on
the direct detection rate of DM particles.


title:
Trends in Ultracool Dwarf Magnetism. I. X-Ray Suppression and Radio
  Enhancement

abstract:
  Although ultracool dwarfs (UCDs) are now known to generate and dissipate
strong magnetic fields, a clear understanding of the underlying dynamo is still
lacking. We have performed X-ray and radio observations of seven UCDs in a
narrow range of spectral type (M6.5-M9.5) but spanning a wide range of
projected rotational velocities (v sin i ~ 3-40 km/s). We have also analyzed
unpublished archival Chandra observations of four additional objects. All of
the newly-observed targets are detected in the X-ray, while only one is
detected in the radio, with the remainder having sensitive upper limits. We
present a database of UCDs with both radio and X-ray measurements and consider
the data in light of the so-called G\"udel-Benz relation (GBR) between magnetic
activity in these bands. Some UCDs have very bright radio emission and faint
X-ray emission compared to what would be expected for rapid rotators, while
others show opposite behavior. We show that UCDs would still be
radio-over-luminous relative to the GBR even if their X-ray emission were at
standard rapid-rotator "saturation" levels. Recent results from Zeeman-Doppler
imaging and geodynamo simulations suggest that rapidly-rotating UCDs may harbor
a bistable dynamo that supports either a stronger, axisymmetric magnetic field
or a weaker, non-axisymmetric field. We suggest that the data can be explained
in a scenario in which strong-field objects obey the GBR while weak-field
objects are radio-over-luminous and X-ray-under-luminous, possibly because of a
population of gyrosynchrotron-emitting coronal electrons that is continuously
replenished by low-energy reconnection events.


title:
Trends in Ultracool Dwarf Magnetism. II. The Inverse Correlation Between
  X-ray Activity and Rotation as Evidence for a Bimodal Dynamo

abstract:
  Observations of magnetic activity indicators in solar-type stars exhibit a
relationship with rotation with an increase until a "saturation" level and a
moderate decrease in activity in the very fastest rotators ("supersaturation").
While X-ray data have suggested that this relationship is strongly violated in
ultracool dwarfs (UCDs; spectral type >M7), the limited number of X-ray
detections has prevented firm conclusions. In this paper, we analyze the X-ray
activity-rotation relation in 38 ultracool dwarfs. Our sample represents the
largest catalog of X-ray active ultracool dwarfs to date, including seven new
and four previously-unpublished Chandra observations presented in a companion
paper. We identify a substantial number of rapidly-rotating UCDs with X-ray
activity extending two orders of magnitude below the expected saturation level
and measure a "supersaturation"-type anticorrelation between rotation and X-ray
activity. The scatter in UCD X-ray activity at a fixed rotation is ~3 times
larger than that in earlier-type stars. We discuss several mechanisms that have
been proposed to explain the data, including centrifugal stripping of the
corona, and find them to be inconsistent with the observed trends. Instead, we
suggest that an additional parameter correlated with both X-ray activity and
rotation is responsible for the observed effects. Building on the results of
Zeeman-Doppler imaging of UCD magnetic fields and our companion study of
radio/X-ray flux ratios, we argue that this parameter is the magnetic field
topology, and that the large scatter in UCD X-ray fluxes reflects the presence
of two dynamo modes that produce distinct topologies.


title:
Next-to-Leading QCD Factorization for Semi-Inclusive Deep Inelastic
  Scattering at Twist-4

abstract:
  Within the framework of a high-twist approach, we calculate the
next-to-leading order (NLO) perturbative QCD corrections to the transverse
momentum broadening in semi-inclusive hadron production in deeply inelastic
$e+A$ collisions, as well as lepton pair production in $p+A$ collisions. With
explicit calculations of both real and virtual contributions, we verify, for
the first time, the factorization theorem at twist 4 in NLO for the
nuclear-enhanced transverse momentum weighted differential cross section and
demonstrate the universality of the associated twist-4 quark-gluon correlation
function. We also identify the QCD evolution equation for the twist-4
quark-gluon correlation function in a large nucleus, which can be solved to
determine the scale dependence of the jet transport parameter in the study of
jet quenching.


title: Doubly-Special Relativity from Quantum Cellular Automata

abstract:
  It is shown how a Doubly-Special Relativity model can emerge from a quantum
cellular automaton description of the evolution of countably many interacting
quantum systems. We consider a one-dimensional automaton that spawns the Dirac
evolution in the relativistic limit of small wave-vectors and masses (in Planck
units). The assumption of invariance of dispersion relations for boosted
observers leads to a non-linear representation of the Lorentz group on the
$(\omega,k)$ space, with an additional invariant given by the wave-vector
$k=\pi /2$. The space-time reconstructed from the $(\omega,k)$ space is
intrinsically quantum, and exhibits the phenomenon of relative locality.


title: The Closest M-Dwarf Quadruple System to the Sun

abstract:
  We report new infrared radial velocity measurements obtained with CSHELL at
NASA's Infrared Telescope Facility that reveal the M3.5 dwarf GJ 867B to be a
single-lined spectroscopic binary with a period of 1.795 $\pm$ 0.017 days. Its
velocity semi-amplitude of 21.4 $\pm$ 0.5 km s$^{-1}$ corresponds to a minimum
mass of 61 $\pm$ 7 M$_{JUP}$; the new companion, which we call GJ 867D, could
be a brown dwarf. Stable astrometric measurements of GJ 867BD obtained with
CTIO's 0.9-m telescope over the last decade exclude the presence of any massive
planetary companions (7-18 M$_{JUP}$) with longer orbital periods (2-10 years)
for the majority of orientations. These complementary observations are also
used to determine the trigonometric distance and proper motion of GJ 867BD; the
measurements are consistent with the HIPPARCOS measured values of the M2 dwarf
GJ 867AC, which is itself a 4.1 day double-lined spectroscopic binary at a
projected separation of 24.5" (216 AU) from GJ 867BD. These new measurements
strengthen the case that GJ 867AC and GJ 867BD are physically associated,
making the GJ 867 system one of only four quadruple systems within 10 pc of the
Sun (d$=$ 8.82 $\pm$0.08 pc) and the only among these with all M-dwarf (or
cooler) components.


title: Dual-fermion approach to interacting disordered fermion systems

abstract:
  We generalize the recently introduced dual fermion (DF) formalism for
disordered fermion systems by including the effect of interactions. For an
interacting disordered system the contributions to the full vertex function
have to be separated into elastic and inelastic scattering processes, and
addressed differently when constructing the DF diagrams. By applying our
approach to the Anderson-Falicov-Kimball model and systematically restoring the
nonlocal correlations in the DF lattice calculation, we show a significant
improvement over the Dynamical Mean-Field Theory and the Coherent Potential
Approximation for both one-particle and two-particle quantities.


title: Transport Equation for Nambu-Goto Strings

abstract:
  We consider a covariant approach to coarse-graining a network of interacting
Nambu-Goto strings. A transport equation is constructed for a spatially flat
Friedmann universe. In Minkowski space and with no spatial dependence this
model agrees with a previous model. Thus it likewise converges to an
equilibrium with a factorizability property. We present an argument that this
property does not depend on a `string chaos' assumption on the correlations
between strings. And in contrast to the earlier model, this transport equation
agrees with conservation equations for a fluid of strings derived from a
different perspective.


title:
EXONEST: Bayesian Model Selection Applied to the Detection and
  Characterization of Exoplanets Via Photometric Variations

abstract:
  EXONEST is an algorithm dedicated to detecting and characterizing the
photometric signatures of exoplanets, which include reflection and thermal
emission, Doppler boosting, and ellipsoidal variations. Using Bayesian
Inference, we can test between competing models that describe the data as well
as estimate model parameters. We demonstrate this approach by testing circular
versus eccentric planetary orbital models, as well as testing for the presence
or absence of four photometric effects. In addition to using Bayesian Model
Selection, a unique aspect of EXONEST is the capability to distinguish between
reflective and thermal contributions to the light curve. A case-study is
presented using Kepler data recorded from the transiting planet KOI-13b. By
considering only the non-transiting portions of the light curve, we demonstrate
that it is possible to estimate the photometrically-relevant model parameters
of KOI-13b. Furthermore, Bayesian model testing confirms that the orbit of
KOI-13b has a detectable eccentricity.


title: Interplay of topology and geometry in frustrated 2d Heisenberg magnets

abstract:
  We investigate two-dimensional frustrated Heisenberg magnets using
non-perturbative renormalization group techniques. These magnets allow for
point-like topological defects which are believed to unbind and drive either a
crossover or a phase transition which separates a low temperature, spin-wave
dominated regime from a high temperature regime where defects are abundant. Our
approach can account for the crossover qualitatively and both the temperature
dependence of the correlation length as well as a broad but well defined peak
in the specific heat are reproduced. We find no signatures of a finite
temperature transition and an accompanying diverging length scale. Our analysis
is consistent with a rapid crossover driven by topological defects.


title: Extremal numbers for odd cycles

abstract:
  We describe the C_{2k+1}-free graphs on n vertices with maximum number of
edges. The extremal graphs are unique except for n = 3k-1, 3k, 4k-2, or 4k-1.
The value of ex(n,C_{2k+1}) can be read out from the works of Bondy, Woodall,
and Bollobas, but here we give a new streamlined proof. The complete
determination of the extremal graphs is also new.
  We obtain that the bound for n_0(C_{2k+1}) is 4k in the classical theorem of
Simonovits, from which the unique extremal graph is the bipartite Turan graph.


title: Curiosity Based Exploration for Learning Terrain Models

abstract:
  We present a robotic exploration technique in which the goal is to learn to a
visual model and be able to distinguish between different terrains and other
visual components in an unknown environment. We use ROST, a realtime online
spatiotemporal topic modeling framework to model these terrains using the
observations made by the robot, and then use an information theoretic path
planning technique to define the exploration path. We conduct experiments with
aerial view and underwater datasets with millions of observations and varying
path lengths, and find that paths that are biased towards locations with high
topic perplexity produce better terrain models with high discriminative power,
especially with paths of length close to the diameter of the world.


title: Galaxy Infall Kinematics as a Test of Modified Gravity

abstract:
  Infrared modifications of General Relativity (GR) can be revealed by
comparing the mass of galaxy clusters estimated from weak lensing to that from
infall kinematics. We measure the 2D galaxy velocity distribution in the
cluster infall region by applying the galaxy infall kinematics (GIK) model
developed by Zu and Weinberg (2013) to two suites of f(R) and Galileon modified
gravity simulations. Despite having distinct screening mechanisms, namely, the
Chameleon and the Vainshtein effects, the f(R) and Galileon clusters exhibit
very similar deviations in their GIK profiles from GR, with ~ 100-200 k/s
enhancement in the characteristic infall velocity at r=5 Mpc/h and 50-100 km/s
broadening in the radial and tangential velocity dispersions across the entire
infall region, for clusters with mass ~ 10^{14} Msol/h at z=0.25. These
deviations are detectable via the GIK reconstruction of the redshift--space
cluster-galaxy cross-correlation function, xi_cg^s(r_p,r_\pi), which shows ~
1-2 Mpc/h increase in the characteristic line-of-sight distance r_\pi^c at
r_p<6 Mpc/h from GR predictions. With overlapping deep imaging and large
redshift surveys in the future, we expect that the GIK modelling of xi_cg^s, in
combination with the stacked weak lensing measurements, will provide powerful
diagnostics of modified gravity theories and the origin of cosmic acceleration.


title: Approximation Errors in Truncated Dimensional Decompositions

abstract:
  The main theme of this paper is error analysis for approximations derived
from two variants of dimensional decomposition of a multivariate function: the
referential dimensional decomposition (RDD) and analysis-of-variance
dimensional decomposition (ADD). New formulae are presented for the lower and
upper bounds of the expected errors committed by bivariately and arbitrarily
truncated RDD approximations when the reference point is selected randomly,
thereby facilitating a means for weighing RDD against ADD approximations. The
formulae reveal that the expected error from the S-variate RDD approximation of
a function of N variables, where $0 \le S < N < \infty$, is at least $2^{S+1}$
times greater than the error from the S-variate ADD approximation.
Consequently, ADD approximations are exceedingly more precise than RDD
approximations. The analysis also finds the RDD approximation to be sub-optimal
for an arbitrarily selected reference point, whereas the ADD approximation
always results in minimum error. Therefore, the RDD approximation should be
used with caution.


title:
Uncertainty Quantification by Alternative Decompositions of Multivariate
  Functions

abstract:
  This article advocates factorized and hybrid dimensional decompositions
(FDD/HDD), as alternatives to analysis-of-variance dimensional decomposition
(ADD), for second-moment statistical analysis of multivariate functions. New
formulae revealing the relationships between component functions of FDD and ADD
are proposed. While ADD or FDD is relevant when a function is strongly additive
or strongly multiplicative, HDD, whether formed linearly or nonlinearly,
requires no specific dimensional hierarchies. Furthermore, FDD and HDD lead to
alternative definitions of effective dimension, reported in the current
literature only for ADD. New closed-form or analytical expressions are derived
for univariate truncations of all three decompositions, followed by
mean-squared error analysis of univariate ADD, FDD, and HDD approximations. The
analysis finds appropriate conditions when one approximation is better than the
other. Numerical results affirm the theoretical finding that HDD is ideally
suited to a general function approximation that may otherwise require
higher-variate ADD or FDD truncations for rendering acceptable accuracy in
stochastic solutions.


title: Instabilities and "phonons" of optical lattices in hollow optical fibers

abstract:
  Instabilities are predicted for a sufficiently long hollow photonic optical
fiber, or "cavity", containing a one dimensional Bose-gas in the presence of a
classical, far red-detuned, confined weak electromagnetic mode. We examine both
a single beam with Bose gas (a type of Brillouin instability) and the case of a
standing wave, or optical lattice. The instabilities of these driven systems
have pronounced spatial structure, of combined modulational instabilities in
the electromagnetic and Bose density fields. Near the critical wave vectors for
the instability the coupled modes of the BEC and light can be interpreted as
"phonons" of the optical lattice. We conjecture these spatially-structured
instabilities for the optical lattice, which we predict at weak fields, develop
into the source of spatially homogeneous heating predicted for strong fields.


title:
Sockpuppet Detection in Wikipedia: A Corpus of Real-World Deceptive
  Writing for Linking Identities

abstract:
  This paper describes the corpus of sockpuppet cases we gathered from
Wikipedia. A sockpuppet is an online user account created with a fake identity
for the purpose of covering abusive behavior and/or subverting the editing
regulation process. We used a semi-automated method for crawling and curating a
dataset of real sockpuppet investigation cases. To the best of our knowledge,
this is the first corpus available on real-world deceptive writing. We describe
the process for crawling the data and some preliminary results that can be used
as baseline for benchmarking research. The dataset will be released under a
Creative Commons license from our project website: http://docsig.cis.uab.edu.


title: Higher algebraic K-theory and tangent spaces to Chow groups

abstract:
  This is a reproduction of my thesis. By using higher K-theory(Chern
character, cyclic homology, effacement theorem and etc), we provide an answer
to a question by Green- Griffiths which says the tangent sequence to
Bloch-Gersten-Quillen sequence is Cousin resolution.


title:
Application of Stochastic Modeling to Analysis of Photometric
  Reverberation Mapping Data

abstract:
  We use both simulated and real quasar light curves to explore modeling
photometric reverberation-mapping (RM) data as a stochastic process. We do this
using modifications to our previously developed RM method based on modeling
quasar variability as a damped random walk. We consider the feasibility of one
and two-band photometric RM and compare the results with those fr om
spectroscopic RM. We find that our method for two-band photometric RM can be
competitive with spectroscopic RM only for strong (large equivalent width)
lines like Halpha and Hbeta, and that the one-band method is also feasible, but
requires very high-precision photometry. We fail to robustly detect Halpha lags
in single-band quasar light curves from OGLE-III and IV despite the outstanding
cadence and time span of the data, on account of photometric uncertainties in
the range 0.02-0.04 mag. Simulations suggest that success could be achieved if
the photometric uncertainties were of order 0.01 mag. Single-band RM for all
lines and two-band RM for lower equivalent width lines are likely only feasible
for statistical estimate s of mean lags for large samples of AGN of similar
properties (e.g., luminosity) rather than for individual quasars. Our approach
is directly applicable to the time-domain programs within ongoing and future
wide-field imaging surveys, and could provide robust lag measurements for an
unprecedented number of systems.


title: Durkheim Project Data Analysis Report

abstract:
  This report describes the suicidality prediction models created under the
DARPA DCAPS program in association with the Durkheim Project
[http://durkheimproject.org/]. The models were built primarily from
unstructured text (free-format clinician notes) for several hundred patient
records obtained from the Veterans Health Administration (VHA). The models were
constructed using a genetic programming algorithm applied to bag-of-words and
bag-of-phrases datasets. The influence of additional structured data was
explored but was found to be minor. Given the small dataset size,
classification between cohorts was high fidelity (98%). Cross-validation
suggests these models are reasonably predictive, with an accuracy of 50% to 69%
on five rotating folds, with ensemble averages of 58% to 67%. One particularly
noteworthy result is that word-pairs can dramatically improve classification
accuracy; but this is the case only when one of the words in the pair is
already known to have a high predictive value. By contrast, the set of all
possible word-pairs does not improve on a simple bag-of-words model.


title: Decomposing the cube into paths

abstract:
  We consider the question of when the $n$-dimensional hypercube can be
decomposed into paths of length $k$. Mollard and Ramras \cite{MR2013} noted
that for odd $n$ it is necessary that $k$ divides $n2^{n-1}$ and that $k\leq
n$. Later, Anick and Ramras \cite{AR2013} showed that these two conditions are
also sufficient for odd $n \leq 2^{32}$ and conjectured that this was true for
all odd $n$. In this note we prove the conjecture.


title:
Solutions of first-order quasilinear systems expressed in Riemann
  invariants

abstract:
  We present a new technique for constructing solutions of quasilinear systems
of first-order partial differential equations, in particular inhomogeneous
ones. A generalization of the Riemann invariants method to the case of
inhomogeneous hyperbolic and elliptic systems is formulated. The algebraization
of these systems enables us to construct certain classes of solutions for which
the matrix of derivatives of the unknown functions is expressible in terms of
special orthogonal matrices. These solutions can be interpreted as nonlinear
superpositions of $k$ waves (or $k$ modes) in the case of hyperbolic (or
elliptic) systems, respectively. Theoretical considerations are illustrated by
several examples of inhomogeneous hydrodynamic-type equations which allow us to
construct solitonlike solutions (bump and kinks) and multiwave (mode)
solutions.


title:
Bayesian estimation of possible causal direction in the presence of
  latent confounders using a linear non-Gaussian acyclic structural equation
  model with individual-specific effects

abstract:
  We consider learning the possible causal direction of two observed variables
in the presence of latent confounding variables. Several existing methods have
been shown to consistently estimate causal direction assuming linear or some
type of nonlinear relationship and no latent confounders. However, the
estimation results could be distorted if either assumption is actually
violated. In this paper, we first propose a new linear non-Gaussian acyclic
structural equation model with individual-specific effects that allows latent
confounders to be considered. We then propose an empirical Bayesian approach
for estimating possible causal direction using the new model. We demonstrate
the effectiveness of our method using artificial and real-world data.


title: Nonlocal Optics of Plasmonic Nanowire Metamaterials

abstract:
  We present an analytical description of the nonlocal optical response of
plasmonic nanowire metamaterials that enable negative refraction, subwavelength
light manipulation, and emission lifetime engineering. We show that dispersion
of optical waves propagating in nanowire media results from coupling of
transverse and longitudinal electromagnetic modes supported by the composite
and derive the nonlocal effective medium approximation for this dispersion. We
derive the profiles of electric field across the unit cell, and use these
expressions to solve the long-standing problem of additional boundary
conditions in calculations of transmission and reflection of waves by nonlocal
nanowire media. We verify our analytical results with numerical solutions of
Maxwell's equations and discuss generalization of the developed formalism to
other uniaxial metamaterials.


title: Mining Maximal Cliques from an Uncertain Graph

abstract:
  We consider mining dense substructures (maximal cliques) from an uncertain
graph, which is a probability distribution on a set of deterministic graphs.
For parameter 0 < {\alpha} < 1, we present a precise definition of an
{\alpha}-maximal clique in an uncertain graph. We present matching upper and
lower bounds on the number of {\alpha}-maximal cliques possible within an
uncertain graph. We present an algorithm to enumerate {\alpha}-maximal cliques
in an uncertain graph whose worst-case runtime is near-optimal, and an
experimental evaluation showing the practical utility of the algorithm.


title:
Quantitative equidistribution for certain quadruples in quasi-random
  groups

abstract:
  In a recent paper (arXiv:1211.6372), Bergelson and Tao proved that if $G$ is
a $D$-quasi-random group, and $x$,$g$ are drawn uniformly and independently
from $G$, then the quadruple $(g,x,gx,xg)$ is roughly equidistributed in the
subset of $G^4$ defined by the constraint that the last two coordinates lie in
the same conjugacy class. Their proof gives only a qualitative version of this
result. The present notes gives a rather more elementary proof which improves
this to an explicit polynomial bound in $D^{-1}$.


title:
Tracking the Evolution of A Coherent Magnetic Flux Rope Continuously
  from the Inner to the Outer Corona

abstract:
  The magnetic flux rope (MFR) is believed to be the underlying magnetic
structure of coronal mass ejections (CMEs). However, it remains unclear how an
MFR evolves into and forms the multi-component structure of a CME. In this
paper, we perform a comprehensive study of an extreme-ultraviolet (EUV) MFR
eruption on 2013 May 22 by tracking its morphological evolution, studying its
kinematics, and quantifying its thermal property. As EUV brightenings begin,
the MFR starts to rise slowly and shows helical threads winding around an axis.
Meanwhile, cool filamentary materials descend spirally down to the
chromosphere. These features provide direct observational evidence of
intrinsically helical structure of the MFR. Through detailed kinematical
analysis, we find that the MFR evolution experiences two distinct phases: a
slow rise phase and an impulsive acceleration phase. We attribute the first
phase to the magnetic reconnection within the quasi-separatrix-layers
surrounding the MFR, and the much more energetic second phase to the fast
magnetic reconnection underneath the MFR. We suggest that the transition
between these two phases be caused by the torus instability. Moreover, we
identify that the MFR evolves smoothly into the outer corona and appears as a
coherent structure within the white light CME volume. The MFR in the outer
corona was enveloped by bright fronts that originated from plasma pile-up in
front of the expanding MFR. The fronts are also associated with the preceding
sheath region followed the outmost MFR-driven shock.


title: Threshold resonance effects in reactive processes

abstract:
  We investigate the effect of near threshold resonances in reactive scattering
at low energy. We find a general type of anomalous behavior of the cross
sections, and illustrate it with a real system (H$_2$ + Cl). For inelastic
processes, the anomalous energy dependence of the total cross sections is given
by $\sigma\sim\varepsilon^{-3/2}$. The standard threshold behavior given by
Wigner's law ($\sigma\sim\varepsilon^{-1/2}$) is eventually recovered at
vanishing energies, but its validity is now limited to a much narrower range of
energies. The universal anomalous behavior leads to reaction rate coefficients
behaving as $K\sim 1/T$ at low temperatures, instead of the expected constant
rate of the Wigner regime. We also provide analytical expressions for s-wave
cross sections, and discuss the implication in ultracold physics and chemistry.


title: CFHTLenS: Co-evolution of galaxies and their dark matter haloes

abstract:
  Galaxy-galaxy weak lensing is a direct probe of the mean matter distribution
around galaxies. The depth and sky coverage of the CFHT Legacy Survey yield
statistically significant galaxy halo mass measurements over a much wider range
of stellar masses ($10^{8.75}$ to $10^{11.3} M_{\odot}$) and redshifts ($0.2 <
z < 0.8$) than previous weak lensing studies. At redshift $z \sim 0.5$, the
stellar-to-halo mass ratio (SHMR) reaches a maximum of $4.0\pm0.2$ percent as a
function of halo mass at $\sim 10^{12.25} M_{\odot}$. We find, for the first
time from weak lensing alone, evidence for significant evolution in the SHMR:
the peak ratio falls as a function of cosmic time from $4.5 \pm 0.3$ percent at
$z \sim 0.7$ to $3.4 \pm 0.2$ percent at $z \sim 0.3$, and shifts to lower
stellar mass haloes. These evolutionary trends are dominated by red galaxies,
and are consistent with a model in which the stellar mass above which star
formation is quenched "downsizes" with cosmic time. In contrast, the SHMR of
blue, star-forming galaxies is well-fit by a power law that does not evolve
with time. This suggests that blue galaxies form stars at a rate that is
balanced with their dark matter accretion in such a way that they evolve along
the SHMR locus. The redshift dependence of the SHMR can be used to constrain
the evolution of the galaxy population over cosmic time.


title: Dynamics in spinor condensates controlled by a microwave dressing field

abstract:
  We experimentally study spin dynamics in a sodium antiferromagnetic spinor
condensate with off-resonant microwave pulses. In contrast to a magnetic field,
a microwave dressing field enables us to explore rich spin dynamics under the
influence of a negative net quadratic Zeeman shift $q_{\rm net}$. We find an
experimental signature to determine the sign of $q_{\rm net}$, and observe
harmonic spin population oscillations at every $q_{\rm net}$ except near each
separatrix in phase space where spin oscillation period diverges. In the
negative and positive $q_{\rm net}$ regions, we also observe a remarkably
different relationship between each separatrix and the magnetization. Our data
confirms an important prediction derived from the mean-field theory:
spin-mixing dynamics in spin-1 condensates substantially depends on the sign of
the ratio of $q_{\rm net}$ and the spin-dependent interaction energy. This work
may thus be the first to use only one atomic species to reveal mean-field spin
dynamics, especially the separatrix, which are predicted to appear differently
in spin-1 antiferromagnetic and ferromagnetic spinor condensates.


title:
The Radio Relics and Halo of El Gordo, a Massive $z=0.870$ Cluster
  Merger

abstract:
  We present 610 MHz and 2.1 GHz imaging of the massive SZE-selected z=0.870
cluster merger ACT-CL J0102-4915 (El Gordo), obtained with the GMRT and the
ATCA, respectively. We detect two complexes of radio relics separated by 3.4'
(1.6 Mpc) along the system's NW-to-SE collision axis that have high integrated
polarizations (33%) and steep spectral indices, consistent with creation via
Fermi acceleration by shocks in the ICM. From the spectral index of the relics,
we compute a Mach number of 2.5^{+0.7}_{-0.3} and shock speed of
2500^{+400}_{-300} km/s. With our ATCA data, we compute the Faraday depth
across the NW relic and find a mean value of 11 rad/m^2 and standard deviation
of 6 rad/m^2. With the integrated line-of-sight gas density derived from new
Chandra observations, our Faraday depth measurement implies B_parallel~0.01 \mu
G in the cluster outskirts. The extremely narrow shock widths in the relics
(<23 kpc) prevent us from placing a meaningful constraint on |B| using cooling
time arguments. In addition to the relics, we detect a large (1.1 Mpc radius),
powerful (log L_1.4[W/Hz]= 25.66+-0.12) radio halo with a Bullet-like
morphology. The spectral-index map of the halo shows the synchrotron spectrum
is flattest near the relics, along the collision axis, and in regions of high
T_gas, all locations associated with recent energy injection. The spatial and
spectral correlation between the halo emission and cluster X-ray properties
supports primary-electron processes like turbulent reacceleration as the halo
production mechanism. The halo's integrated 610 MHz to 2.1 GHz spectral index
is 1.2+-0.1, consistent with the cluster's high T_gas in view of previously
established global scaling relations. El Gordo is the highest-redshift cluster
known to host a radio halo and/or radio relics, and provides new constraints on
the non-thermal physics in clusters at z>0.6. [abridged]


title: Brane Inflation and Moduli Stabilization on Twisted Tori

abstract:
  We consider supergravity compactifications on 6-dimensional twisted tori,
which are 5-torus fibrations of the circle. The motion of branes on such
manifolds can lead to power-law potentials at low energy, that may be useful
for inflation. We classify the possible low energy potentials one can obtain by
wrapping branes on different cycles of the fibre. Turning to the problem of
moduli stabilization in such models, we prove a no-go result for solutions with
parametrically small cosmological constant, under certain assumptions for the
orientifolds and D-branes. We also consider the role of discrete Wilson lines
in moduli stabilization on general closed manifolds, and show that gauge
invariance restricts their contributions to the effective potential. We derive
the allowed discrete Wilson lines in massive Type IIA supergravity on twisted
tori. We conclude with a detailed example, computing the effective potentials
in a class of models involving a twisted torus and an orientifold 6-plane.


title: Gauge Theories, D-Branes and Holography

abstract:
  Based on a generalization of the string theoretic concept of D-brane probe,
we propose a new approach to large N gauge theories which makes the holographic
properties manifest. For any gauge theory, we define from first principles an
effective action for a fixed number of "probe" D-branes in the presence of N
"background" D-branes on which the gauge theory lives. This effective action is
shown to encode all the information about the large N gauge theory. The
analysis of the planar diagram expansion which computes the effective action
yields a simple and generic mechanism explaining the emergence of holographic
space dimensions: the probe D-branes move in a higher dimensional dual
holographic space-time. The construction yields a new perspective on the notion
of bulk space-time locality and draws unexpected links with some aspects of the
't Hooft Abelian projection ideas. It also provides a new non-perturbative
approximation scheme, able to capture both the weak and strong coupling
regimes. We sketchily illustrate the basic ideas on a few examples, including
the pure four dimensional Yang-Mills theory.


title:
X-ray Measurement of the Spin-Down of Calvera: a Radio- and
  Gamma-ray-Quiet Pulsar

abstract:
  We measure spin-down of the 59 ms X-ray pulsar Calvera by comparing the
XMM-Newton discovery data from 2009 with new Chandra timing observations taken
in 2013. Its period derivative is P-dot = (3.19+/-0.08)e-15, which corresponds
to spin-down luminosity E-dot = 6.1e35 erg/s, characteristic age tau_c =
P/2P-dot = 2.9e5 yr, and surface dipole magnetic field strength B_s = 4.4e11 G.
These values rule out a mildly recycled pulsar, but Calvera could be an
orphaned central compact object (anti-magnetar), with a magnetic field that was
initially buried by supernova debris and is now reemerging and approaching
normal strength. We also performed unsuccessful searches for high-energy
gamma-rays from Calvera in both imaging and timing of >100 MeV Fermi photons.
Even though the distance to Calvera is uncertain by an order of magnitude, an
upper limit of d < 2 kpc inferred from X-ray spectra implies a gamma-ray
luminosity limit of < 3.3e32 erg/s, which is less than that of any pulsar of
comparable E-dot. Calvera shares some properties with PSR J1740+1000, a young
radio pulsar that we show by virtue of its lack of proper motion was born
outside of the Galactic disk. As an energetic, high-Galactic-latitude pulsar,
Calvera is unique in being undetected in both radio and gamma-rays to faint
limits, which should place interesting constraints on models for particle
acceleration and beam patterns in pulsar magnetospheres.