cssi/SciSciGPT-SciSciNet huggingface dataset:
Transport spectroscopy of low disorder silicon tunnel barriers with and without Sb implants

We present transport measurements of silicon MOS split gate structures with and without Sb implants. We observe classical point contact (PC) behavior that is free of any pronounced unintentional resonances at liquid He temperatures. The implanted device has resonances superposed on the PC transport indicative of transport through the Sb donors. We fit the differential conductance to a rectangular tunnel barrier model with a linear barrier height dependence on source-drain voltage and non-linear dependence on gate bias. Effects such as Fowler-Nordheim (FN) tunneling and image charge barrier lowering (ICBL) are considered. Barrier heights and widths are estimated for the entire range of relevant biases. The barrier heights at the locations of some of the resonances for the implanted tunnel barrier are between 15-20 meV, which are consistent with transport through shallow partially hybridized Sb donors. The dependence of width and barrier height on gate voltage is found to be linear over a wide range of gate bias in the split gate geometry but deviates considerably when the barrier becomes large and is not described completely by standard 1D models such as FN or ICBL effects.
Exploring N = 1 SYM (2+1): the stress-tensor correlator

Abstract The evaluation of field theoretic correlators at strong couplings is especially interesting in the light of recently discovered string/field theory correspondences. We present a calculation of the stress-tensor correlator in N = 1 SYM theory in 2+1 dimensions. We calculate this object numerically with the method of supersymmetric discrete light-cone quantization (SDLCQ) at large Nc. For small distances we reproduce the conformal field theory result with the correlator behaving like 1/r6. In the large r limit the correlator is determined by the (massless) BPS states of the theory. We find a critical value of the coupling where the correlator goes to zero in this limit. This critical coupling is shown to grow linearly with the square root of the transverse momentum resolution.
On the Stability of Strange Dwarf Hybrid Stars

We investigate the stability of "strange dwarfs": white-dwarf-sized stars with a density discontinuity between a small dense core of quark matter and a thick low-density mantle of degenerate electrons. Previous work on strange dwarfs suggested that such a discontinuity could stabilize stars that would have been classified as unstable by the conventional criteria based on extrema in the mass–radius relation. We investigate the stability of such stars by numerically solving the Sturm–Liouville equations for the lowest-energy modes of the star. We find that the conventional criteria are correct, and strange dwarfs are not stable.
Concentration Dependence of Diffusion-Limited Reaction Rates and Its Consequences

Simulations show that molecular diffusion on 2D biological surfaces can lead to reaction rates that depend nontrivially on concentrations, an insight with profound impacts on the stability of certain biomolecular systems.
Ricci flow of conformally compact metrics

Abstract In this paper we prove that given a smoothly conformally compact asymptotically hyperbolic metric there is a short-time solution to the Ricci flow that remains smoothly conformally compact and asymptotically hyperbolic. We adapt recent results of Schnurer, Schulze and Simon to prove a stability result for conformally compact Einstein metrics sufficiently close to the hyperbolic metric.
Inviscid Damping Near the Couette Flow in a Channel

We prove asymptotic stability of the Couette flow for the 2D Euler equations in the domain $$\mathbb {T}\times [0,1]$$. More precisely we prove that if we start with a small and smooth perturbation (in a suitable Gevrey space) of the Couette flow, then the velocity field converges strongly to a nearby shear flow. Our solutions are defined on the compact set $$\mathbb {T}\times [0,1]$$ (“the channel”) and therefore have finite energy. The vorticity perturbation, which is initially assumed to be supported in the interior of the channel, will remain supported in the interior of the channel at all times, will be driven to higher frequencies by the linear flow, and will converge weakly to another shear flow as $$t\rightarrow \infty $$.
Functional Subsystems and Quantum Redundancy in Photosynthetic Light Harvesting

The Fenna–Matthews–Olson (FMO) antennae complex, responsible for light harvesting in green sulfur bacteria, consists of three monomers, each with seven chromophores. Here we show that multiple subsystems of the seven chromophores can transfer energy from either chromophore 1 or 6 to the reaction center with an efficiency matching or in many cases exceeding that of the full seven chromophore system. In the FMO complex, these functional subsystems support multiple quantum pathways for efficient energy transfer that provide a built-in quantum redundancy. There are many instances of redundancy in nature, providing reliability and protection, and in photosynthetic light harvesting this quantum redundancy provides protection against the temporary or permanent loss of one or more chromophores. The complete characterization of functional subsystems within the FMO complex offers a detailed map of the energy flow within the FMO complex, which has potential applications to the design of more efficient photovoltaic d...
Connectivity-aware traffic phase scheduling for heterogeneously connected vehicles

We consider a transportation system of heterogeneously connected vehicles, where not all vehicles are able to communicate. Heterogeneous connectivity in transportation systems is coupled to practical constraints such that (i) not all vehicles may be equipped with devices having communication interfaces, (ii) some vehicles may not prefer to communicate due to privacy and security reasons, and (iii) communication links are not perfect and packet losses and delay occur in practice. In this context, it is crucial to develop control algorithms by taking into account the heterogeneity. In this paper, we particularly focus on making traffic phase scheduling decisions. We develop a connectivity-aware traffic phase scheduling algorithm for heterogeneously connected vehicles that increases the intersection efficiency (in terms of the average number of vehicles that are allowed to pass the intersection) by taking into account the heterogeneity. The simulation results show that our algorithm significantly improves the efficiency of intersections as compared to the baselines.
Loss in long-storage-time optical cavities.

Long-storage-time Fabry-Perot cavities are a core component of many precision measurement experiments. Optical loss in such cavities is a critical parameter in determining their performance; however, it is very difficult to determine a priori from independent characterisation of the individual cavity mirrors. Here, we summarise three techniques for directly measuring this loss in situ and apply them to a high-finesse, near-concentric, 2 m system. Through small modifications of the cavity’s length, we explore optical loss as a function of beam spot size over the 1–3 mm range. In this regime we find that optical loss is relatively constant at around 5 ppm per mirror and shows greater dependence on the positions of the beam spots on the cavity optics than on their size. These results have immediate consequences for the application of squeezed light to advanced gravitational-wave interferometers.
Graph Meta Learning via Local Subgraphs

Prevailing methods for graphs require abundant label and edge information for learning. When data for a new task are scarce, meta-learning can learn from prior experiences and form much-needed inductive biases for fast adaption to new tasks. Here, we introduce G-Meta, a novel meta-learning algorithm for graphs. G-Meta uses local subgraphs to transfer subgraph-specific information and learn transferable knowledge faster via meta gradients. G-Meta learns how to quickly adapt to a new task using only a handful of nodes or edges in the new task and does so by learning from data points in other graphs or related, albeit disjoint label sets. G-Meta is theoretically justified as we show that the evidence for a prediction can be found in the local subgraph surrounding the target node or edge. Experiments on seven datasets and nine baseline methods show that G-Meta outperforms existing methods by up to 16.3%. Unlike previous methods, G-Meta successfully learns in challenging, few-shot learning settings that require generalization to completely new graphs and never-before-seen labels. Finally, G-Meta scales to large graphs, which we demonstrate on a new Tree-of-Life dataset comprising of 1,840 graphs, a two-orders of magnitude increase in the number of graphs used in prior work.
CFT description of small objects in AdS

By the AdS/CFT correspondence, the expectation value of certain local operators in the CFT is given by the asymptotic value of supergravity fields. We show that these local expectation values contain a remarkable amount of information about small sources deep inside AdSp × Sq. In particular, they contain essentially all the multipole moments. More importantly, one can use them to determine the size of a spherical source. This is not a small effect: The size appears in an exponentially large contribution to the expectation values. This provides an easy way for the CFT to distinguish stars from black holes with the same mass, or to distinguish different ``giant graviton" configurations.
Spectral Methods for Time-dependent Studies of Accretion Flows. II. Two-dimensional Hydrodynamic Disks with Self-Gravity

Spectral methods are well suited for solving hydrodynamic problems in which the self-gravity of the flow needs to be considered. Because Poisson's equation is linear, the numerical solution for the gravitational potential for each individual mode of the density can be precomputed, thus reducing substantially the computational cost of the method. In this second paper, we describe two different approaches to computing the gravitational field of a two-dimensional flow with pseudospectral methods. For situations in which the density profile is independent of the third coordinate (i.e., an infinite cylinder), we use a standard Poisson solver in spectral space. On the other hand, for situations in which the density profile is a δ-function along the third coordinate (i.e., an infinitesimally thin disk), or any other function known a priori, we perform a direct integration of Poisson's equation using a Green's functions approach. We devise a number of test problems to verify the implementations of these two methods. Finally, we use our method to study the stability of polytropic, self-gravitating disks. We find that when the polytropic index Γ is ≤4/3, Toomre's criterion correctly describes the stability of the disk. However, when Γ > 4/3 and for large values of the polytropic constant K, the numerical solutions are always stable, even when the linear criterion predicts the contrary. We show that in the latter case, the minimum wavelength of the unstable modes is larger than the extent of the unstable region, and hence the local linear analysis is inapplicable.
Longitude Floer homology and the Whitehead double

We define the longitude Floer homology of a knot K ⊂ S 3 and show that it is a topological invariant of K. Some basic properties of these homology groups are derived. In particular, we show that they distinguish the genus of K. We also make explicit computations for the (2,2n+1) torus knots. Finally a correspondence between the longitude Floer homology of K and the Ozsvath-Szabo Floer homology of its Whitehead double KL is obtained. AMS Classification 57R58; 57M25, 57M27
ByRDiE: Byzantine-Resilient Distributed Coordinate Descent for Decentralized Learning

Distributed machine learning algorithms enable learning of models from datasets that are distributed over a network without gathering the data at a centralized location. While efficient distributed algorithms have been developed under the assumption of faultless networks, failures that can render these algorithms nonfunctional occur frequently in the real world. This paper focuses on the problem of Byzantine failures, which are the hardest to safeguard against in distributed algorithms. While Byzantine fault tolerance has a rich history, existing work does not translate into efficient and practical algorithms for high-dimensional learning in fully distributed (also known as decentralized) settings. In this paper, an algorithm termed Byzantine-resilient distributed coordinate descent is developed and analyzed that enables distributed learning in the presence of Byzantine failures. Theoretical analysis (convex settings) and numerical experiments (convex and nonconvex settings) highlight its usefulness for high-dimensional distributed learning in the presence of Byzantine failures.
On gapped phases with a continuous symmetry and boundary operators

We discuss the role of compact symmetry groups, G, in the classification of gapped ground state phases of quantum spin systems. We consider two representations of G on infinite subsystems. First, in arbitrary dimensions, we show that the ground state spaces of models within the same G-symmetric phase carry equivalent representations of the group for each finite or infinite sublattice on which they can be defined and on which they remain gapped. This includes infinite systems with boundaries or with non-trivial topologies. Second, for two classes of one-dimensional models, by two different methods, for G=SU(2) in one, and G\subset SU(d), in the other we construct explicitly an `excess spin' operator that implements rotations of half of the infinite chain on the GNS Hilbert space of the ground state of the full chain. Since this operator is constructed as the limit of a sequence of observables, the representation itself is, in principle, experimentally observable. We claim that the corresponding unitary representation of G is closely related to the representation found at the boundary of half-infinite chains. We conclude with determining the precise relation between the two representations for the class of frustration-free models with matrix product ground states.
Reconstruction of Weakly Simple Polygons from Their Edges

We address the problem of reconstructing a polygon from the multiset of its edges. Given n line segments in the plane, find a polygon with n vertices whose edges are these segments, or report that none exists. It is easy to solve the problem in O(nlog n) time if we seek an arbitrary polygon or a simple polygon. We show that the problem is NP-complete for weakly simple polygons, that is, a polygon whose vertices can be perturbed by at most &#x1d700;, for any &#x1d700; > 0, to obtain a simple polygon. We give O(n)-time algorithms for reconstructing weakly simple polygons: when all segments are collinear or the segment endpoints are in general position. These results extend to the variant in which the segments are directed. We study related problems for the case that the union of the n input segments is connected. (i) If each segment can be subdivided into several segments, find the minimum number of subdivision points to form a weakly simple polygon. (ii) If new line segments can be added, find the minimum total length of ...
Incongruences for modular forms and applications to partition functions

Abstract The study of arithmetic properties of coefficients of modular forms f ( τ ) = ∑ a ( n ) q n has a rich history, including deep results regarding congruences in arithmetic progressions. Recently, work of C.-S. Radu, S. Ahlgren, B. Kim, N. Andersen, and S. Lobrich have employed the q-expansion theory of P. Deligne and M. Rapoport in order to determine more about where these congruences can occur. Here, we apply the method to a large class of modular forms, and in particular to several noteworthy examples, including generalized Frobenius partitions and the two mock theta functions f ( q ) and ω ( q ) .
Light dynamics in nonlinear trimers and twisted multicore fibers

Novel photonic structures such as multicore fibers and graphene based arrays present unique opportunities to manipulate and control the propagation of light. Here, we discuss nonlinear dynamics for structures with a few (2–6) elements for which linear and nonlinear properties can be tuned. Specifically, we show how nonlinearity, coupling, and parity–time (&#x1d4ab;&#x1d4af;) symmetric gain/loss relate to existence, stability and in general, dynamical properties of nonlinear optical modes. The main emphasis of our presentation will be on systems with few degrees of freedom, most notably couplers, trimers and generalizations thereof to systems with six nodes.
The Morphology of IRC+10420's Circumstellar Ejecta

Images of the circumstellar ejecta associated with the post-red supergiant IRC+10420 show a complex ejecta with visual evidence for episodic mass loss. In this paper, we describe the transverse motions of numerous knots, arcs, and condensations in the inner ejecta measured from second epoch Hubble Space Telescope/WFPC2 images. When combined with the radial motions for several of the features, the total space motion and direction of the outflows show that they were ejected at different times, in different directions, and presumably from separate regions on the surface of the star. These discrete structures in the ejecta are kinematically distinct from the general expansion of the nebula and their motions are dominated by their transverse velocities. They are apparently all moving within a few degrees of the plane of the sky. We are thus viewing IRC+10420 nearly pole-on and looking nearly directly down onto its equatorial plane. We also discuss the role of surface activity and magnetic fields on IRC+10420's recent mass-loss history.
ALMA Observations of the Interaction of a Radio Jet with Molecular Gas in Minkowski's Object

We use ALMA to detect and image CO (1-0) emission from Minkowski's Object, a dwarf galaxy that is interacting with a radio jet from a nearby elliptical galaxy. These observations are the first to detect molecular gas in Minkowski's Object. We estimate the range in the mass of molecular gas in Minkowski's Object assuming two different values of the ratio of the molecular gas mass to the CO luminosity, $\alpha_{\rm CO}$. For the Milky Way value of $\alpha_{\rm CO}=4.6~M_{\odot}{\rm (K~km~s^{-1}~pc^2)^{-1}}$ we obtain a molecular gas mass of $M_{\rm H_2} =3.0 \times 10^7~M_{\odot}$, 6% of the HI gas mass. We also use the prescription of Narayanan et al. (2012) to estimate an $\alpha_{\rm CO}=27~M_{\odot}{\rm (K~km~s^{-1}~pc^2)^{-1}}$, in which case we obtain $M_{\rm H_2} =1.8 \times 10^8~M_{\odot}$, 36% of the HI mass. The observations are consistent with previous claims of star formation being induced in Minkowski's Object via the passage of the radio jet, and it therefore being a rare local example of positive feedback from an AGN. In particular, we find highly efficient star formation, with gas depletion timescales $\sim 5\times 10^7 - 3\times 10^8$yr (for assumed values of $\alpha_{\rm CO}=4.6$ and $27~M_{\odot}{\rm (K~km~s^{-1}~pc^2)^{-1}}$, respectively) in the upstream regions of Minkowski's Object that were struck first by the jet, and less efficient star formation downstream. We discuss the implications of this observation for models of jet induced star formation and radio mode feedback in massive galaxies.
Self-avoiding modes of motion in a deterministic Lorentz lattice gas

We study the motion of a particle on the two-dimensional honeycomb lattice, whose sites are occupied by either flipping rotators or flipping mirrors, which scatter the particle according to a deterministic rule. For both types of scatterers we find a new type of motion that has not been observed in a Lorentz Lattice gas, where the particleʼs trajectory is a self-avoiding walk between returns to its initial position. We show that this behavior is a consequence of the deterministic scattering rule and the particular class of initial scatterer configurations we consider. Since self-avoiding walks are one of the main tools used to model the growth of crystals and polymers, the particleʼs motion in this class of systems is potentially important for the study of these processes.
Compositeness, triviality and bounds on critical exponents for fermions and magnets

Abstract We present simple arguments that explain how theories that share the same global symmetries can fall into different universality classes depending on whether their Goldstone bosons are realized as fundamental or composite. In particular, for the theories with fundamental fermions that undergo chiral symmetry breaking and those with fundamental scalars that exhibit a magnetic phase transition, different bounds on the critical exponents δ and η follow. We observe that in four dimensions the logarithmic scaling violations enter into the Equation of State of scalar theories, such as λφ 4 , and fermionic models, such as Nambu-Jona-Lasinio, in qualitatively different ways. These observations lead to useful approaches for analyzing lattice simulations of a wide class of model field theories. Our results imply that λφ 4 cannot be a good guide to understanding the possible triviality of spinor QED.
Epitaxial bulk acoustic wave resonators as highly coherent multi-phonon sources for quantum acoustodynamics.

Solid-state quantum acoustodynamic (QAD) systems provide a compact platform for quantum information storage and processing by coupling acoustic phonon sources with superconducting or spin qubits. The multi-mode composite high-overtone bulk acoustic wave resonator (HBAR) is a popular phonon source well suited for QAD. However, scattering from defects, grain boundaries, and interfacial/surface roughness in the composite transducer severely limits the phonon relaxation time in sputter-deposited devices. Here, we grow an epitaxial-HBAR, consisting of a metallic NbN bottom electrode and a piezoelectric GaN film on a SiC substrate. The acoustic impedance-matched epi-HBAR has a power injection efficiency >99% from transducer to phonon cavity. The smooth interfaces and low defect density reduce phonon losses, yielding (f × Q) and phonon lifetimes up to 1.36 × 1017 Hz and 500 µs respectively. The GaN/NbN/SiC epi-HBAR is an electrically actuated, multi-mode phonon source that can be directly interfaced with NbN-based superconducting qubits or SiC-based spin qubits. Acoustic resonators may find application for qubit coupling in compact quantum information and processing systems. Here the authors show a multi-phonon source with high quality factors and long phonon lifetimes via epitaxial high-overtone bulk acoustic resonators.
The entropy of bulk quantum fields and the entanglement wedge of an evaporating black hole

Bulk quantum fields are often said to contribute to the generalized entropy $$ \frac{A}{4{G}_N}+{S}_{\mathrm{bulk}} $$ only at O(1). Nonetheless, in the context of evaporating black holes, O(1/GN ) gradients in Sbulk can arise due to large boosts, introducing a quantum extremal surface far from any classical extremal surface. We examine the effect of such bulk quantum effects on quantum extremal surfaces (QESs) and the resulting entanglement wedge in a simple two-boundary 2d bulk system defined by Jackiw-Teitelboim gravity coupled to a 1+1 CFT. Turning on a coupling between one boundary and a further external auxiliary system which functions as a heat sink allows a two-sided otherwise-eternal black hole to evaporate on one side. We find the generalized entropy of the QES to behave as expected from general considerations of unitarity, and in particular that ingoing information disappears from the entanglement wedge after a scambling time $$ \frac{\beta }{2\pi}\log \varDelta S+O(1) $$ in accord with expectations for holographic implementations of the Hayden-Preskill protocol. We also find an interesting QES phase transition at what one might call the Page time for our process.
On the Convergence Properties of a K-step Averaging Stochastic Gradient Descent Algorithm for Nonconvex Optimization

Despite their popularity, the practical performance of asynchronous stochastic gradient descent methods (ASGD) for solving large scale machine learning problems are not as good as theoretical results indicate. We adopt and analyze a synchronous K-step averaging stochastic gradient descent algorithm which we call K-AVG. We establish the convergence results of K-AVG for nonconvex objectives and explain why the K-step delay is necessary and leads to better performance than traditional parallel stochastic gradient descent which is a special case of K-AVG with $K=1$. We also show that K-AVG scales better than ASGD. Another advantage of K-AVG over ASGD is that it allows larger stepsizes. On a cluster of $128$ GPUs, K-AVG is faster than ASGD implementations and achieves better accuracies and faster convergence for \cifar dataset.
Consistent Approximations for the Optimal Control of Constrained Switched Systems---Part 1: A Conceptual Algorithm

Switched systems, or systems whose control parameters include a continuous-valued input and a discrete-valued input which corresponds to the mode of the system that is active at a particular instance in time, have shown to be highly effective in modeling a variety of physical phenomena. Unfortunately, the construction of an optimal control algorithm for such systems has proved difficult since it demands some form of optimal mode scheduling. In a pair of papers, we construct a first order optimization algorithm to address this problem. Our approach, which we prove in this paper converges to local minimizers of the constrained optimal control problem, first relaxes the discrete-valued input, performs traditional optimal control, and then projects the constructed relaxed discrete-valued input back to a pure discrete-valued input by employing an extension to the classical chattering lemma that we formalize. In the second part of this pair of papers, we describe how this conceptual algorithm can be recast in o...
Levi-flat hypersurfaces with real analytic boundary

Let X be a Stein manifold of dimension at least 3. Given a compact codimension 2 real analytic submanifold M of X, that is the boundary of a compact Levi-flat hypersurface H, we study the regularity of H. Suppose that the CR singularities of M are an O(X)-convex set. For example, suppose M has only finitely many CR singularities, which is a generic condition. Then H must in fact be a real analytic submanifold. If M is real algebraic, it follows that H is real algebraic and in fact extends past M, even near CR singularities. To prove these results we provide two variations on a theorem of Malgrange, that a smooth submanifold contained in a real analytic subvariety of the same dimension is itself real analytic. We prove a similar theorem for submanifolds with boundary, and another one for subanalytic sets.
Herschel Observations of Dusty Debris Disks

We present results from two Herschel observing programs using the Photodetector Array Camera and Spectrometer. During three separate campaigns, we obtained Herschel data for 24 stars at 70, 100, and 160 microns. We chose stars that were already known or suspected to have circumstellar dust based on excess infrared emission previously measured with IRAS or Spitzer, and used Herschel to examine long-wavelength properties of the dust. Fifteen stars were found to be uncontaminated by background sources, and possess infrared emission most likely due to a circumstellar debris disk. We analyzed the properties of these debris disks to better understand the physical mechanisms responsible for dust production and removal. Seven targets were spatially resolved in the Herschel images. Based on fits to their spectral energy distributions, nine disks appear to have two temperature components. Of these nine, in three cases, the warmer dust component is likely the result of a transient process rather than a steady state collisional cascade. The dust belts at four stars are likely stirred by an unseen planet, and merit further investigation.
Statistical Mechanics of Transcription-Factor Binding Site Discovery Using Hidden Markov Models.

Hidden Markov Models (HMMs) are a commonly used tool for inference of transcription factor (TF) binding sites from DNA sequence data. We exploit the mathematical equivalence between HMMs for TF binding and the “inverse” statistical mechanics of hard rods in a one-dimensional disordered potential to investigate learning in HMMs. We derive analytic expressions for the Fisher information, a commonly employed measure of confidence in learned parameters, in the biologically relevant limit where the density of binding sites is low. We then use techniques from statistical mechanics to derive a scaling principle relating the specificity (binding energy) of a TF to the minimum amount of training data necessary to learn it.
A Flexible Bayesian Framework for Assessing Habitability with Joint Observational and Model Constraints

The catalog of stellar evolution tracks discussed in our previous work is meant to help characterize exoplanet host-stars of interest for follow-up observations with future missions like JWST. However, the utility of the catalog has been predicated on the assumption that we would precisely know the age of the particular host-star in question; in reality, it is unlikely that we will be able to accurately estimate the age of a given system. Stellar age is relatively straightforward to calculate for stellar clusters, but it is difficult to accurately measure the age of an individual star to high precision. Unfortunately, this is the kind of information we should consider as we attempt to constrain the long-term habitability potential of a given planetary system of interest. This is ultimately why we must rely on predictions of accurate stellar evolution models, as well a consideration of what we can observably measure (stellar mass, composition, orbital radius of an exoplanet) in order to create a statistical framework wherein we can identify the best candidate systems for follow-up characterization. In this paper we discuss a statistical approach to constrain long-term planetary habitability by evaluating the likelihood that at a given time of observation, a star would have a planet in the 2 Gy continuously habitable zone (CHZ2). Additionally, we will discuss how we can use existing observational data (i.e. data assembled in the Hypatia catalog and the Kepler exoplanet host star database) for a robust comparison to the catalog of theoretical stellar models.
Warped radion dark matter

Warped scenarios offer an appealing solution to the hierarchy problem. We consider a non-trivial deformation of the basic Randall-Sundrum framework that has a KK-parity symmetry. This leads to a stable particle beyond the Standard Model, that is generically expected to be the first KK-parity odd excitation of the radion field. We consider the viability of the KK-radion as a DM candidate in the context of thermal and non-thermal production in the early universe. In the thermal case, the KK-radion can account for the observed DM density when the radion decay constant is in the natural multi-TeV range. We also explore the effects of coannihilations with the first KK excitation of the RH top, as well as the effects of radion-Higgs mixing, which imply mixing between the KK-radion and a KK-Higgs (both being KK-parity odd). The non-thermal scenario, with a high radion decay constant, can also lead to a viable scenario provided the reheat temperature and the radion decay constant take appropriate values, although the reheat temperature should not be much higher than the TeV scale. Direct detection is found to be feasible if the DM has a small (KK-parity odd) Higgs admixture. Indirect detection via a photon signal from the galactic center is an interesting possibility, while the positron and neutrino fluxes from KK-radion annihilations are expected to be rather small. Colliders can probe characteristic aspects of the DM sector of warped scenarios with KK-parity, such as the degeneracy between the radion and the KK-radion (DM) modes.
Experimental robustness of Fourier ptychography phase retrieval algorithms

Fourier ptychography is a new computational microscopy technique that provides gigapixel-scale intensity and phase images with both wide field-of-view and high resolution. By capturing a stack of low-resolution images under different illumination angles, an inverse algorithm can be used to computationally reconstruct the high-resolution complex field. Here, we compare and classify multiple proposed inverse algorithms in terms of experimental robustness. We find that the main sources of error are noise, aberrations and mis-calibration (i.e. model mis-match). Using simulations and experiments, we demonstrate that the choice of cost function plays a critical role, with amplitude-based cost functions performing better than intensity-based ones. The reason for this is that Fourier ptychography datasets consist of images from both brightfield and darkfield illumination, representing a large range of measured intensities. Both noise (e.g. Poisson noise) and model mis-match errors are shown to scale with intensity. Hence, algorithms that use an appropriate cost function will be more tolerant to both noise and model mis-match. Given these insights, we propose a global Newton’s method algorithm which is robust and accurate. Finally, we discuss the impact of procedures for algorithmic correction of aberrations and mis-calibration.
On type-preserving representations of the four-punctured sphere group

We give counterexamples to a question of Bowditch that asks whether a nonelementary type-preserving representation W 1.†g;n/ ! PSL.2IR/ of a punctured surface group that sends every nonperipheral simple closed curve to a hyperbolic element must be Fuchsian. The counterexamples come from relative Euler class 1 representations of the four-punctured sphere group. We also show that the mapping class group action on each nonextremal component of the character space of typepreserving representations of the four-punctured sphere group is ergodic, which confirms a conjecture of Goldman for this case. The main tool we use are Kashaev and Penner’s lengths coordinates of the decorated character spaces.
Orientation-sensed Optomechanical Accelerometers based on Exceptional Points

We propose an on-chip parity-time symmetric optomechanical platform that detects ultra-small directional accelerations with high signal to noise ratio. The platform consists of two balanced gain/loss cavities embedded in a multilayer photonic crystal with an adjustable layer coupled to mechanical springs. Its deflections due to an acceleration are sensed as a spectral detuning of a transmittance peak near an exceptional point degeneracy.
Radiative muon capture by a proton in chiral perturbation theory

Abstract The first measurement of the radiative muon capture (RMC) rate on a proton was recently carried out at TRIUMF. The TRIUMF group analyzed the RMC rate, ΓRMCexp, in terms of the theoretical formula of Beder and Fearing, and found the surprising result that gP≡fP(q2=−0.88mμ2) is 1.5 times the value expected from PCAC. To assess the reliability of the theoretical framework used by the TRIUMF group to relate ΓRMC to the pseudoscalar form factor fP, we calculate ΓRMC in chiral perturbation theory, which provides a systematic framework to describe all the vertices involved in RMC, fulfilling gauge-invariance and chiral-symmetry requirements in a transparent manner. As a first step we present a chiral perturbation calculation at tree level which includes sub-leading order terms.
On the Density Distribution in Star-forming Interstellar Clouds

We use deep adaptive mesh refinement simulations of isothermal self-gravitating supersonic turbulence to study the imprints of gravity on the mass density distribution in molecular clouds. The simulations show that the density distribution in self-gravitating clouds develops an extended power-law tail at high densities on top of the usual lognormal. We associate the origin of the tail with self-similar collapse solutions and predict the power index values in the range from ?7/4 to ?3/2 that agree with both simulations and observations of star-forming molecular clouds.
An Attempt to Describe Frequency Correlations among kHz QPOs and HBOs by Two-Armed Nearly Vertical Oscillations

We examine whether the two-armed ($m=2$) vertical p-mode oscillations trapped in the innermost region of magnetized accretion disks with finite disk thickness can describe kHz QPOs and HBOs in LMXBs. First, we derive the frequency-frequency correlation of the two basic oscillations (both are fundamental modes in the vertical direction, but one is the fundamental and the other the first overtone in the radial direction), and compare it with the observed frequency correlation of twin kHz QPOs. Results show that the calculated frequency correlation can well describe observed correlation with reasonable values of parameters. Second, we examine whether the observed frequency correlation between kHz QPOs and HBO can be described by regarding HBO as the first overtone oscillation in the vertical direction (and the fundamental in the radial direction). The results suggest that i) innermost parts of disks on the horizontal branch are strongly diminished in their vertical thickness (presumably by hot coronae) and ii) the branch is roughly a sequence of variations of magnetic fields or disk temperature.
Flavor symmetry for quarks and leptons

Present data on neutrino masses and mixing favor the highly symmetric tribimaximal neutrino mixing matrix which suggests an underlying flavor symmetry. A systematic study of non-abelian finite groups of order g ≤ 31 reveals that tribimaximal mixing can be derived not only from the well known tetrahedral flavor symmetry T ≡ A4, but also by using the binary tetrahedral symmetry T' ≡ SL2(F3) which does not contain the tetrahedral group as a subgroup. T' has the further advantage that it can also neatly accommodate the quark masses including a heavy top quark.
Evaluating Quasilocal Energy and Solving Optimal Embedding Equation at Null Infinity

We study the limit of quasilocal energy defined in Wang and Yau (Phys Rev Lett 102(2):021101, 2009; Commun Math Phys 288(3):919–942, 2009) for a family of spacelike 2-surfaces approaching null infinity of an asymptotically flat spacetime. It is shown that Lorentzian symmetry is recovered and an energy-momentum 4-vector is obtained. In particular, the result is consistent with the Bondi–Sachs energy-momentum at a retarded time. The quasilocal mass in Wang and Yau (Phys Rev Lett 102(2):021101, 2009; Commun Math Phys 288(3):919–942, 2009) is defined by minimizing quasilocal energy among admissible isometric embeddings and observers. The solvability of the Euler-Lagrange equation for this variational problem is also discussed in both the asymptotically flat and asymptotically null cases. Assuming analyticity, the equation can be solved and the solution is locally minimizing in all orders. In particular, this produces an optimal reference hypersurface in the Minkowski space for the spatial or null exterior region of an asymptotically flat spacetime.
Braided Tensor Categories and Extensions of Vertex Operator Algebras

Let V be a vertex operator algebra satisfying suitable conditions such that in particular its module category has a natural vertex tensor category structure, and consequently, a natural braided tensor category structure. We prove that the notions of extension (i.e., enlargement) of V and of commutative associative algebra, with uniqueness of unit and with trivial twist, in the braided tensor category of V-modules are equivalent.
Localization and non-renormalization in Chern-Simons theory

We revisit and clarify some aspects of perturbative renormalization in pure Chern-Simons theory by means of a localization principle associated with an underlying supersymmetry. This perspective allows the otherwise perturbative one-loop shifts to be interpreted as nonperturbative consequences of a non-renormalization theorem, while providing a unified understanding of their origin (particularly in the case of Wilson lines). We illustrate this approach explicitly for SU(2) Chern-Simons theory in flat space, on Seifert manifolds, and on a solid torus.
The Anatomy of the Column Density Probability Distribution Function (N-PDF)

The column density probability distribution function (N-PDF) of GMCs has been used as a diagnostic of star formation. Simulations and analytic predictions have suggested the N-PDF is composed of a low density lognormal component and a high density power-law component, tracing turbulence and gravitational collapse, respectively. In this paper, we study how various properties of the true 2D column density distribution create the shape, or "anatomy" of the PDF. We test our ideas and analytic approaches using both a real, observed, PDF based on Herschel observations of dust emission as well as a simulation that uses the ENZO code. Using a dendrogram analysis, we examine the three main components of the N-PDF: the lognormal component, the power-law component, and the transition point between these two components. We find that the power-law component of an N-PDF is the summation of N-PDFs of power-law substructures identified by the dendrogram algorithm. We also find that the analytic solution to the transition point between lognormal and power-law components proposed by Burkhart, Stalpes & Collins (2017) is applicable when tested on observations and simulations, within the uncertainties. We reconfirm and extend the results of Lombardi, Alves & Lada (2015), which stated that the lognormal component of the N-PDF is difficult to constrain due to the artificial choice of the map area. Based on the resulting anatomy of the N-PDF, we suggest avoiding analyzing the column density structures of a star forming region based solely on fits to the lognormal component of an N-PDF. We also suggest applying the N-PDF analysis in combination with the dendrogram algorithm, to obtain a more complete picture of the global and local environments and their effects on the density structures.
On asymptotic dimension of groups

We prove a version of the countable union theorem for asymp- totic dimension and we apply it to groups acting on asymptotically nite dimensional metric spaces. As a consequence we obtain the following nite dimensionality theorems. A) An amalgamated product of asymptotically nite dimensional groups has nite asymptotic dimension: asdimAC B< 1 . B) Suppose that G 0 is an HNN extension of a group G with asdimG < 1. Then asdimG 0 <1. C) Suppose that is Davis' group constructed from a group with asdim <1. Then asdim <1. AMS Classication 20H15; 20E34, 20F69
The head and tail conjecture for alternating knots

The normalized colored Jones polynomial JN;L.q/ for a link L is a sequence of Laurent polynomials in the variable q , ie JN;L 2 ZŒq; q . This sequence is defined for N 2 so that J2;L.q/ is the ordinary Jones polynomial, and JN;U D 1 where U is the unknot. For links L with an odd number of components (including all knots), JL;N is actually in ZŒq; q . For links with an even number of components, qJL;N 2 ZŒq; q .
Causal network learning with non-invertible functional relationships

Abstract Discovery of causal relationships from observational data is an important problem in many areas. Several recent results have established the identifiability of causal directed acyclic graphs (DAGs) with non-Gaussian and/or nonlinear structural equation models (SEMs). Focusing on nonlinear SEMs defined by non-invertible functions, which exist in many data domains, a novel test is proposed for non-invertible bivariate causal models. Algorithms are further developed to incorporate this test in structure learning of DAGs that contain both linear and nonlinear causal relations. Extensive numerical comparisons show that the proposed algorithms outperform existing DAG learning methods in identifying causal graphical structures. The practical application of the methods is illustrated by learning causal networks for combinatorial binding of transcription factors from ChIP-Seq data.
Prime Running Functions

We study arithmetic functions Φ(x;d,a), called prime running functions, whose value at x sums the gaps between primes pk≡a(mod d) below x and the next following prime pk+1, up to x. (The following ...
Electron paramagnetic resonance g-tensors from state interaction spin-orbit coupling density matrix renormalization group

We present a state interaction spin-orbit coupling method to calculate electron paramagnetic resonance g-tensors from density matrix renormalization group wavefunctions. We apply the technique to compute g-tensors for the TiF3 and CuCl42- complexes, a [2Fe-2S] model of the active center of ferredoxins, and a Mn4CaO5 model of the S2 state of the oxygen evolving complex. These calculations raise the prospects of determining g-tensors in multireference calculations with a large number of open shells.
The Synoptic Swift Synergy—Catching Gamma-Ray Bursts Before They Fly

The advent of large panoramic photometric surveys of the sky offers the possibly of exploring the association of gamma-ray bursts (GRBs) with supernovae. To date, a few GRBs have been connected possibly with supernovae: GRB 980425-SN 1998bw, GRB 011121-SN 2001ke, GRB 970228, and GRB 980326. A combination of a large detection rate of GRBs and rapid coverage of a large portion of the sky to faint magnitude limits offers the possibility of detecting a supernova preceding an associated GRB or at least placing limits on the rate of association between these two phenomena and the time delay between them. This would provide important constraints on theoretical models for GRBs.
Pre-Training Transformers as Energy-Based Cloze Models

We introduce Electric, an energy-based cloze model for representation learning over text. Like BERT, it is a conditional generative model of tokens given their contexts. However, Electric does not use masking or output a full distribution over tokens that could occur in a context. Instead, it assigns a scalar energy score to each input token indicating how likely it is given its context. We train Electric using an algorithm based on noise-contrastive estimation and elucidate how this learning objective is closely related to the recently proposed ELECTRA pre-training method. Electric performs well when transferred to downstream tasks and is particularly effective at producing likelihood scores for text: it re-ranks speech recognition n-best lists better than language models and much faster than masked language models. Furthermore, it offers a clearer and more principled view of what ELECTRA learns during pre-training.
Thermal Kinetic Inductance Detectors for Ground-Based Millimeter-Wave Cosmology

We show measurements of thermal kinetic inductance detectors (TKIDs) intended for millimeter-wave cosmology in the 200–300 GHz atmospheric window. The TKID is a type of bolometer which uses the kinetic inductance of a superconducting resonator to measure the temperature of the thermally isolated bolometer island. We measure bolometer thermal conductance, time constant, and noise equivalent power. We also measure the quality factor of our resonators as the bath temperature varies to show they are limited by effects consistent with coupling to two-level systems.