cssi/SciSciGPT-SciSciNet huggingface dataset:
On the Relationship Between Probabilistic Circuits and Determinantal Point Processes.

Scaling probabilistic models to large realistic problems and datasets is a key challenge in machine learning. Central to this effort is the development of tractable probabilistic models (TPMs): models whose structure guarantees efficient probabilistic inference algorithms. The current landscape of TPMs is fragmented: there exist various kinds of TPMs with different strengths and weaknesses. Two of the most prominent classes of TPMs are determinantal point processes (DPPs) and probabilistic circuits (PCs). This paper provides the first systematic study of their relationship. We propose a unified analysis and shared language for discussing DPPs and PCs. Then we establish theoretical barriers for the unification of these two families, and prove that there are cases where DPPs have no compact representation as a class of PCs. We close with a perspective on the central problem of unifying these tractable models.
An Unusual Application of Cramér-Rao Inequality to Prove the Attainable Lower Bound for a Ratio of Complicated Gamma Functions

A specific function f(r) involving a ratio of complicated gamma functions depending upon a real variable r(> 0) is handled. Details are explained regarding how this function f(r) appeared naturally for our investigation with regard to its behavior when r belongs to R+. We determine explicitly where this function attains its unique minimum. In doing so, quite unexpectedly the customary Cramer-Rao inequality comes into play in order to nail down a valid proof of the required lower bound for f(r) and locating where is that lower bound exactly attained.
On multivariate fractional random fields: Tempering and operator-stable laws

Abstract In this paper, we define a new and broad family of vector-valued random fields called tempered operator fractional operator-stable random fields (TRF, for short). TRF is typically non-Gaussian and generalizes tempered fractional stable stochastic processes. TRF comprises moving average and harmonizable-type subclasses that are constructed by tempering (matrix-) homogeneous, matrix-valued kernels in time- and Fourier-domain stochastic integrals with respect to vector-valued, strictly operator-stable random measures. We establish the existence and fundamental properties of TRF. Assuming both Gaussianity and isotropy, we show the equivalence between certain moving average and harmonizable subclasses of TRF. In addition, we establish sample path properties in the scalar-valued case for several Gaussian instances.
Rapid purification and metabolomic profiling of synaptic vesicles from mammalian brain.

Neurons communicate by the activity-dependent release of small-molecule neurotransmitters packaged into synaptic vesicles (SVs). Although many molecules have been identified as neurotransmitters, technical limitations have precluded a full metabolomic analysis of synaptic vesicle content. Here, we present a workflow to rapidly isolate SVs and to interrogate their metabolic contents at high-resolution using mass spectrometry. We validated the enrichment of glutamate in SVs of primary cortical neurons using targeted polar metabolomics. Unbiased and extensive global profiling of SVs isolated from these neurons revealed that the only detectable polar metabolites they contain are the established neurotransmitters glutamate and GABA. In addition, we adapted the approach to enable quick capture of SVs directly from brain tissue and determined the neurotransmitter profiles of diverse brain regions in a cell-type specific manner. The speed, robustness, and precision of this method to interrogate SV contents will facilitate novel insights into the chemical basis of neurotransmission.
Size of bulk fermions in the SYK model

The study of quantum gravity in the form of the holographic duality has uncovered and motivated the detailed investigation of various diagnostics of quantum chaos. One such measure is the operator size distribution, which characterizes the size of the support region of an operator and its evolution under Heisenberg evolution. In this work, we examine the role of the operator size distribution in holographic duality for the Sachdev-Ye-Kitaev (SYK) model. Using an explicit construction of AdS2 bulk fermion operators in a putative dual of the low temperature SYK model, we study the operator size distribution of the boundary and bulk fermions. Our result provides a direct derivation of the relationship between (effective) operator size of both the boundary and bulk fermions and bulk SL(2; ℝ) generators.
Probabilistic forecasting using deep generative models

A fundamental problem in Numerical Weather Prediction (NWP) is the generation of ensembles to capture the probability of future states of the atmosphere. This research presents a new methodology to generate analogs using deep generative models, an emerging class of deep learning approaches. The goal is to train a deep generative model using a set of historical forecasts and associated observations, and to use it to entirely or partially replace the need to maintain a potentially very large dataset. In this research, this new methodology is compared with the Analog Ensemble (AnEn) approach, a computationally efficient solution to generate analogs. The proposed approach promises to reduce the amount of memory required to produce the probabilistic forecast by several orders of magnitude. Results show that the generative model solution is constant time without performing any search, saving a considerable amount of time even in the presence of huge historical datasets.
Reinterpreting π-stacking

The nature of π-π interactions has long been debated. The term "π-stacking" is considered by some to be a misnomer, in part because overlapping π-electron densities are thought to incur steric repulsion, and the physical origins of the widely-encountered "slip-stacked" motif have variously been attributed to either sterics or electrostatics, in competition with dispersion. Here, we use quantum-mechanical energy decomposition analysis to investigate π-π interactions in supramolecular complexes of polycyclic aromatic hydrocarbons, ranging in size up to realistic models of graphene, and for comparison we perform the same analysis on stacked complexes of polycyclic saturated hydrocarbons, which are cyclohexane-based analogues of graphane. Our results help to explain the short-range structure of liquid hydrocarbons that is inferred from neutron scattering, trends in melting-point data, the interlayer separation of graphene sheets, and finally band gaps and observation of molecular plasmons in graphene nanoribbons. Analysis of intermolecular forces demonstrates that aromatic π-π interactions constitute a unique and fundamentally quantum-mechanical form of non-bonded interaction. Not only do stacked π-π architectures enhance dispersion, but quadrupolar electrostatic interactions that may be repulsive at long range are rendered attractive at the intermolecular distances that characterize π-stacking, as a result of charge penetration effects. The planar geometries of aromatic sp2 carbon networks lead to attractive interactions that are "served up on a molecular pizza peel", and adoption of slip-stacked geometries minimizes steric (rather than electrostatic) repulsion. The slip-stacked motif therefore emerges not as a defect induced by electrostatic repulsion but rather as a natural outcome of a conformational landscape that is dominated by van der Waals interactions (dispersion plus Pauli repulsion), and is therefore fundamentally quantum-mechanical in its origins. This reinterpretation of the forces responsible for π-stacking has important implications for the manner in which non-bonded interactions are modeled using classical force fields, and for rationalizing the prevalence of the slip-stacked π-π motif in protein crystal structures.
On URANS Congruity with Time Averaging: Analytical Laws Suggest Improved Models

The standard 1-equation model of turbulence was first derived by Prandtl and has evolved to be a common method for practical flow simulations. Five fundamental laws that any URANS model should satisfy are $$ \begin{array} [c]{ccc} 1. &{} \text {Time window:} &{} \begin{array} [c]{c} \tau \downarrow 0\,\text {implies}\, v_{\text {URANS}}\rightarrow u_{\text {NSE}}\, \& \\ \tau \uparrow \text { implies }\nu _{T}\uparrow \end{array} \\ 2. &{} l(x)=0 \text { at walls:} &{} l(x)\rightarrow 0\text { as }x\rightarrow walls,\\ 3. &{} \text {Bounded energy:} &{} \sup _{t}\int \frac{1}{2}|v(x,t)|^{2}+k(x,t)dx<\infty \\ 4. &{} \begin{array} [c]{c} \text {Statistical }\\ \text {equilibrium:} \end{array} &{} \lim \sup _{T\rightarrow \infty }\frac{1}{T}\int _{0}^{T}\varepsilon _{\text {model}}(t)dt=\mathcal {O}\left( \frac{U^{3}}{L}\right) \\ 5. &{} \begin{array} [c]{c} \text {Backscatter}\\ \text {possible:} \end{array}&\text {(without negative viscosities)} \end{array} $$ This report proves that a kinematic specification of the model’s turbulence lengthscale by $$ l(x,t)=\sqrt{2}k^{1/2}(x,t)\tau , $$ where \(\tau \) is the time filter window, results in a 1-equation model satisfying Conditions 1, 2, 3, 4 without model tweaks, adjustments or wall damping multipliers.
Dimensional Dependence of the Hydrodynamics of Core-collapse Supernovae

A major goal over the last decade has been understanding which multidimensional effects are crucial in facilitating core-collapse supernova (CCSN) explosions. Unfortunately, much of this work has necessarily assumed axisymmetry. In this work, we present analyses of simplified two-dimensional (2D) and three-dimensional (3D) CCSN models with the goal of comparing the hydrodynamics in setups that differ only in dimension. Not surprisingly, we find many differences between 2D and 3D models. While some differences are subtle and perhaps not crucial, others are dramatic and make interpreting 2D models problematic. In particular, axisymmetric models produce excess power at the largest spatial scales, power that has been deemed critical in previous explosion models. Nevertheless, our 3D models, which have an order of magnitude less power than 2D models on large scales, explode earlier. Since explosions occur earlier in 3D than in 2D, the vigorous large-scale sloshing is either not critical in any dimension or the explosion mechanism operates differently in 2D and 3D. On the other hand, we find that the average parcel of matter in the gain region has been exposed to net heating for up to 30% longer in 3D than in 2D, an effect we attribute to the differing characters of turbulence in 2D and 3D. We suggest that this effect plays a prominent role in producing earlier explosions in 3D. Finally, we discuss a simple model for the runaway growth of buoyant bubbles that is able to quantitatively account for the growth of the shock radius and predicts a critical luminosity relation.
Forming Gliese 876 through Smooth Disk Migration

We run a suite of dissipative N-body simulations to determine which regions of phase space for smooth disk migration are consistent with the GJ876 system, an M-dwarf hosting three planets orbiting in a chaotic 4:2:1 Laplace resonance. We adopt adaptive mesh refinement (AMR) methods that are commonly used in hydrodynamical simulations to efficiently explore the parameter space defined by the semimajor axis and eccentricity damping timescales. We find that there is a large region of phase space that produces systems in the chaotic Laplace resonance and a smaller region consistent with the observed eccentricities and libration amplitudes for the resonant angles. Under the assumptions of Type I migration for the outer planet, we translate these damping timescales into constraints on the protoplanetary disk surface density and thickness. When we strongly (weakly) damp the eccentricities of the inner two Laplace planets, these timescales correspond to disk surface densities around ten thousand (a few hundred) grams per square centimeter and disk aspect ratios between 1% and 10%. Additionally, smooth migration produces systems with a range of chaotic timescales, from decades and centuries to upward of thousands of years. In agreement with previous studies, the less chaotic regions of phase space coincide with the system being in a low-energy double apsidal corotation resonance. Our detailed modeling of multiplanetary systems coupled with our AMR exploration method enhances our ability to map out the parameter space of planet formation models and is well suited to study other resonant chain systems such as Trappist-1, Kepler-60, and others.
Breaking bivariate records

We establish a fundamental property of bivariate Pareto records for independent observations uniformly distributed in the unit square. We prove that the asymptotic conditional distribution of the number of records broken by an observation given that the observation sets a record is Geometric with parameter 1/2.
Profile Likelihood Ratio Analysis Techniques for Rare Event Signals

The Cryogenic Dark Matter Search (CDMS) II uses crystals operated at milliKelvin temperature to search for dark matter. We present the details of the profile likelihood analysis of 140.2 kg-day exposure from the final data set of the CDMS II Si detectors that revealed three WIMP-candidate events. We found that this result favors a WIMP+background hypothesis over the known-background-only hypothesis at the 99.81 % confidence level. This paper is dedicated to the description of the profile likelihood analysis dedicated to the CDMSII-Si data and discusses such analysis techniques in the scope of rare event searches.
The BMO-Dirichlet problem for elliptic systems in the upper half-space and quantitative characterizations of VMO

The first author would like to express his gratitude to the University of Missouri-Columbia (USA), for its support and hospitality while he was visiting this institution. The first author acknowledges financial support from the Spanish Ministry of Economy and Competitiveness, through the \Severo Ochoa Programme for Centres of Excellence in R&D" (SEV-2015-0554). He also acknowledges that the research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP7/2007-2013)/ ERC agreement no. 615112 HAPDEGMT. The second author has been supported in part by the Simons Foundation grant #426669, the third author has been supported in part by the Simons Foundation grant #318658, while the fourth author has been supported in part by the Simons Foundation grant #281566, and by a University of Missouri Research Leave grant.
Models, methods and network topology: Experimental design for the study of interference

Abstract How should a network experiment be designed to achieve high statistical power? Experimental treatments on networks may spread. Randomizing assignment of treatment to nodes enhances learning about the counterfactual causal effects of a social network experiment and also requires new methodology (ex. Aronow and Samii, 2017a , Bowers et al., 2013 , Toulis and Kao, 2013 ). In this paper we show that the way in which a treatment propagates across a social network affects the statistical power of an experimental design. As such, prior information regarding treatment propagation should be incorporated into the experimental design. Our findings justify reconsideration of standard practice in circumstances where units are presumed to be independent even in simple experiments: information about treatment effects is not maximized when we assign half the units to treatment and half to control. We also present an example in which statistical power depends on the extent to which the network degree of nodes is correlated with treatment assignment probability. We recommend that researchers think carefully about the underlying treatment propagation model motivating their study in designing an experiment on a network.
Conjoining uncooperative societies facilitates evolution of cooperation

Social structure affects the emergence and maintenance of cooperation. Here, we study the evolutionary dynamics of cooperation in fragmented societies, and show that conjoining segregated cooperation-inhibiting groups, if done properly, rescues the fate of collective cooperation. We highlight the essential role of intergroup ties, which sew the patches of the social network together and facilitate cooperation. We point out several examples of this phenomenon in actual settings. We explore random and non-random graphs, as well as empirical networks. In many cases, we find a marked reduction of the critical benefit-to-cost ratio needed for sustaining cooperation. Our finding gives hope that the increasing worldwide connectivity, if managed properly, can promote global cooperation.
Development of a broadband reflective T-filter for voltage biasing high-Q superconducting microwave cavities

We present the design of a reflective stop-band filter based on quasi-lumped elements that can be utilized to introduce large dc and low-frequency voltage biases into a low-loss superconducting coplanar waveguide (CPW) cavity. Transmission measurements of the filter are seen to be in good agreement with simulations and demonstrate insertion losses greater than 20 dB in the range of 3–10 GHz. Moreover, transmission measurements of the CPW's fundamental mode demonstrate that loaded quality factors exceeding 105 can be achieved with this design for dc voltages as large as 20 V and for the cavity operated in the single-photon regime. This makes the design suitable for use in a number of applications including qubit-coupled mechanical systems and circuit QED.
Improving Cross-Corpus Speech Emotion Recognition with Adversarial Discriminative Domain Generalization (ADDoG)

Automatic speech emotion recognition provides computers with critical context to enable user understanding. While methods trained and tested within the same dataset have been shown successful, they often fail when applied to unseen datasets. To address this, recent work has focused on adversarial methods to find more generalized representations of emotional speech. However, many of these methods have issues converging, and only involve datasets collected in laboratory conditions. In this paper, we introduce Adversarial Discriminative Domain Generalization (ADDoG), which follows an easier to train “meet in the middle“ approach. The model iteratively moves representations learned for each dataset closer to one another, improving cross-dataset generalization. We also introduce Multiclass ADDoG, or MADDoG, which is able to extend the proposed method to more than two datasets, simultaneously. Our results show consistent convergence for the introduced methods, with significantly improved results when not using labels from the target dataset. We also show how, in most cases, ADDoG and MADDoG can be used to improve upon baseline state-of-the-art methods when target dataset labels are added and in-the-wild data are considered. Even though our experiments focus on cross-corpus speech emotion, these methods could be used to remove unwanted factors of variation in other settings.
Universal deformation rings and dihedral 2-groups

Let k be an algebraically closed field of characteristic 2, and let W be the ring of infinite Witt vectors over k. Suppose that D is a dihedral 2-group. We prove that the universal deformation ring R(D, V) of an endo-trivial kD-module V is always isomorphic to W [/2x/2]. As a consequence, we obtain a similar result for modules V with stable endomorphism ring k belonging to an arbitrary nilpotent block with defect group D. This confirms, for such V, conjectures on the ring structure of the universal deformation ring of V that had previously been shown for V belonging to cyclic blocks or to blocks with Klein four defect groups.
Models of the Mass-ejection Histories of Pre-planetary Nebulae. III. The Shaping of Lobes by Post-AGB Winds

We develop a physical framework for interpreting high-resolution images of pre planetary nebule ("prePNe") with pairs of candle shaped lobes. We use hydrodynamical models to infer the historical properties of the flows injected from the nucleus that shape the lobes into standard forms. First, we find a suitable set of parameters of a fast, collimated, tapered flow that is actively reshaped by an exterior slow AGB wind and that nicely fits the basic shape, kinematics, mass, and momenta of this class of prePNe. Next we vary the most influential parameters of this "baseline" model-such as density, speed, and geometry-to see how changes in the flow parameters affect the nebular observables after 900y. Several generic conlusions emerge, such as the injected flows that create the hollow candle-shaped lobes must be light, "tapered", and injected considerably faster than the lobe expansion speed. Multi-polar and starfish prePNe probably evolve from wide angle flows in which thin-shell instabilites corrugate their leading edges. We show how the common linear relationship of Doppler shift and position along the lobe is a robust outcome the interaction of tapered diverging streamlines with the lobes' curved walls. Finally we probe how magnetic fields affect the basline model by adding a toroidal field to the injected baseline flow. Examples of prePNe and PNe that may have been magnetically shaped are listed. We conclude that the light, field-free, tapered baseline flow model is an successful and universal pardigm for unravelling the histories of lobe formation in prePNe.
Toroidal dipole response in a multifold double-ring metamaterial

The toroidal response is numerically investigated in a multifold double-ring metamaterials at the antibonding magnetic-dipole mode (i.e., antiparallel magnetic dipoles in one double-ring fold). This intriguing toroidal resonance in metamaterials is considered as a result of the magnetoelectric effect due to the broken balance of the electric near-field environment. We demonstrate that the toroidal dipole response in metamaterials can improve the quality factor of the resonance spectrum. In viewing of the design flexibility on the double-ring geometry, such toroidal metamaterials will offer advantages in application potentials of toroidal dipolar moment.
Kontsevich’s noncommutative numerical motives

In this article we prove that Kontsevich’s category NC_(num)(k)_F of noncommutative numerical motives is equivalent to the one constructed by the authors in [Marcolli and Tabuada, Noncommutative motives, numerical equivalence, and semisimplicity, Amer. J. Math., to appear, available at arXiv:1105.2950]. As a consequence, we conclude that NC_(num)(k)_F is abelian semi-simple as conjectured by Kontsevich.
Charge state dynamics and optically detected electron spin resonance contrast of shallow nitrogen-vacancy centers in diamond

The authors demonstrate that diamond surface conditions can strongly affect charge state stability, and that changes in charge state dynamics can also decrease the optically detected electron spin resonance contrast.
Kähler-Ricci flow on stable Fano manifolds

We study the Kahler-Ricci flow on Fano manifolds. We show that if the curvature is bounded along the flow and if the manifold is K-polystable and asymptotically Chow semistable, then the flow converges exponentially fast to a Kahler-Einstein metric.
Dynamic Sensor Selection for Reliable Spectrum Sensing via E-Optimal Criterion

Reliable and efficient spectrum sensing through dynamic selection of a subset of spectrum sensors is studied. The problem of selecting K sensor measurements from a set of M potential sensors is considered where K
Sparse sums of squares on finite abelian groups and improved semidefinite lifts

Let G be a finite abelian group. This paper is concerned with nonnegative functions on G that are sparse with respect to the Fourier basis. We establish combinatorial conditions on subsets $${\mathcal {S}}$$S and $${\mathcal {T}}$$T of Fourier basis elements under which nonnegative functions with Fourier support $${\mathcal {S}}$$S are sums of squares of functions with Fourier support $${\mathcal {T}}$$T. Our combinatorial condition involves constructing a chordal cover of a graph related to G and $${\mathcal {S}}$$S (the Cayley graph $${{\mathrm{Cay}}}(\widehat{G},{\mathcal {S}})$$Cay(G^,S)) with maximal cliques related to $${\mathcal {T}}$$T. Our result relies on two main ingredients: the decomposition of sparse positive semidefinite matrices with a chordal sparsity pattern, as well as a simple but key observation exploiting the structure of the Fourier basis elements of G (the characters of G). We apply our general result to two examples. First, in the case where $$G = {\mathbb {Z}}_2^n$$G=Z2n, by constructing a particular chordal cover of the half-cube graph, we prove that any nonnegative quadratic form in n binary variables is a sum of squares of functions of degree at most $$\left\lceil n/2 \right\rceil $$n/2, establishing a conjecture of Laurent. Second, we consider nonnegative functions of degree d on $${\mathbb {Z}}_N$$ZN (when d divides N). By constructing a particular chordal cover of the dth power of the N-cycle, we prove that any such function is a sum of squares of functions with at most $$3d\log (N/d)$$3dlog(N/d) nonzero Fourier coefficients. Dually this shows that a certain cyclic polytope in $${\mathbb {R}}^{2d}$$R2d with N vertices can be expressed as a projection of a section of the cone of positive semidefinite matrices of size $$3d\log (N/d)$$3dlog(N/d). Putting $$N=d^2$$N=d2 gives a family of polytopes in $${\mathbb {R}}^{2d}$$R2d with linear programming extension complexity $$\varOmega (d^2)$$Ω(d2) and semidefinite programming extension complexity $$O(d\log (d))$$O(dlog(d)). To the best of our knowledge, this is the first explicit family of polytopes $$(P_d)$$(Pd) in increasing dimensions where $${{\mathrm{xc_{\text {PSD}}}}}(P_d) = o({{\mathrm{xc_{\text {LP}}}}}(P_d))$$xcPSD(Pd)=o(xcLP(Pd)), where $${{\mathrm{xc_{\text {PSD}}}}}$$xcPSD and $${{\mathrm{xc_{\text {LP}}}}}$$xcLP are respectively the SDP and LP extension complexity.
A review of the 0.1 reconnection rate problem

A long-standing problem in magnetic reconnection is to explain why it tends to proceed at or below a normalized rate of 0.1. This article gives a review of observational and numerical evidence for this rate and discusses recent theoretical work addressing this problem. Some remaining open questions are summarized.
Demons and Abelian projection QCD: action and crossover

Abstract SAPQCD, the Abelian projection QCD (APQCD) action, is evaluated using the demon method. For SU(2), SAPQCD at strong coupling is essentially the compact QED (CQED) action with β CQED = 1 2 β SU(2) : extended and higher representation plaquettes are absent. Since CQED deconfines when βCQED>∼ 1, this relation must break down as βSU(2) → 2. Indeed we find SAPQCD mutates: near βSU(2) ∼ 2 it gains additional operators, including an exogenous negative magnetic monopole mass shift. SAPQCD for SU(3) has similar behavior. The Appendix gives a brief explanation of the demon method.
Blazar jet physics in the age of Fermi

Abstract : The impact of the Fermi Gamma-ray Space Telescope on blazar research is reviewed. This includes a brief description of the Fermi Large Area Telescope, a summary of the various classes of extragalactic sources found in the First Large Area Telescope AGN Catalog, and more detailed discussion of the flat spectrum radio quasar 3C454.3 and the BL Lac object PKS 2155-304. Some theoretical studies related to ongoing blazar research with Fermi are mentioned, including implications of gamma-ray observations of radio galaxies on blazar unification scenarios, variability in colliding shells, and whether blazars are sources of ultra-high energy cosmic rays.
Automatic microscopic cell counting by use of unsupervised adversarial domain adaptation and supervised density regression

Accurate cell counting in microscopic images is important for medical diagnoses and biological studies. However, manual cell counting is very time-consuming, tedious, and prone to subjective errors. We propose a new density regression-based method for automatic cell counting that reduces the need to manually annotate experimental images. A supervised learning-based density regression model (DRM) is trained with annotated synthetic images (the source domain) and their corresponding ground truth density maps. A domain adaptation model (DAM) is built to map experimental images (the target domain) to the feature space of the source domain. By use of the unsupervised learning-based DAM and supervised learning-based DRM, a cell density map of a given target image can be estimated, from which the number of cells can be counted. Results from experimental immunofluorescent microscopic images of human embryonic stem cells demonstrate the promising performance of the proposed counting method.
Verification of Spent Nuclear Fuel in Sealed Dry Storage Casks via Measurements of Cosmic-Ray Muon Scattering

Most countries allow international inspectors to access their nuclear facilities, to verify that plutonium in spent nuclear fuel is not being diverted to a clandestine weapon program. Unfortunately, the heavily shielded storage casks that protect workers and the public from highly radioactive spent fuel also prevent typical radiographic probes, such as photons or neutrons, from verifying that fuel is actually present in the cask. This paper shows that measurements of the scattering of cosmic-ray muons by spent fuel in casks are sensitive to the removal of fuel, potentially solving a longstanding problem in international nuclear safeguards.
Microresonator-based high-resolution gas spectroscopy.

We report the first demonstration of a microresonator-based tunable mode-locked frequency comb source. We achieve a mode-hop-free tuning range of 16 GHz by simultaneously tuning both the pump laser and the cavity resonance while keeping the system in a multi-soliton mode-locked state. The optical spectrum spans 2520–4125 cm−1 (2.425–3.970 μm) pumping at 3508 cm−1 (2.850 μm) in a silicon microresonator with a comb line spacing of 4.23 cm−1 (127 GHz). Our scanning technique can be used to increase the effective resolution of the microresonator-based comb spectroscopy. As a proof-of-principle demonstration, we record the absorption spectrum of the rovibrational transitions of the υ3 and υ2+(υ4+υ5)+0 bands of acetylene. We measure absorption features as narrow as 0.21 cm−1 (6.4 GHz) full width at half-maximum at a frequency sampling step of 80 MHz.
Systematic quantum corrections to screening in thermonuclear fusion

We develop a series expansion of the plasma screening length away from the classical limit in powers of 2. It is shown that the leading-order quantum correction decreases the fusion rate by approximately 2%. We also calculate the next higher order quantum correction, which turns out to be approximately an order of magnitude smaller.
Does Social Support (Expressed in Post Titles) Elicit Comments in Online Substance Use Recovery Forums

Individuals recovering from substance use often seek social support (emotional and informational) on online recovery forums, where they can both write and comment on posts, expressing their struggles and successes. A common challenge in these forums is that certain posts (some of which may be support seeking) receive no comments. In this work, we use data from two Reddit substance recovery forums: /r/Leaves and /r/OpiatesRecovery, to determine the relationship between the social supports expressed in the titles of posts and the number of comments they receive. We show that the types of social support expressed in post titles that elicit comments vary from one substance use recovery forum to the other.
Almost all Steiner triple systems have perfect matchings

We show that for any n divisible by 3, almost all order-n Steiner triple systems have a perfect matching (also known as a parallel class or resolution class). In fact, we prove a general upper bound on the number of perfect matchings in a Steiner triple system and show that almost all Steiner triple systems essentially attain this maximum. We accomplish this via a general theorem comparing a uniformly random Steiner triple system to the outcome of the triangle removal process, which we hope will be useful for other problems. Our methods can also be adapted to other types of designs; for example, we sketch a proof of the theorem that almost all Latin squares have transversals.
Incentive Compatibility in Stochastic Dynamic Systems

The classic Vickrey–Clarke–Groves (VCG) mechanism ensures incentive compatibility, i.e., truth-telling is a dominant strategy for all agents, for a static one-shot game. However, it does not appear to be feasible to construct mechanisms that ensure dominance of dynamic truth-telling for agents comprised of general stochastic dynamic systems. The agents’ intertemporal net utilities depend on future controls and payments, and a direct extension of the VCG mechanism does not guarantee incentive compatibility. This article shows that such a stochastic dynamic extension does exist for the special case of linear-quadratic-Gaussian (LQG) agents. In fact, it achieves subgame perfect dominance of truth-telling. This is accomplished through a construction of a sequence of layered payments over time that decouples the intertemporal effect of current bids on future net utilities if system parameters are known and agents are rational. An important motivating example arises in power systems where an independent system operator has to ensure balance of generation and consumption at all times, while ensuring social efficiency, i.e., maximization of the sum of the utilities of all agents. It is also necessary to satisfy budget balance and individual rationality. However, in general, even for static one-shot games, there is no mechanism that simultaneous satisfies these requirements while being incentive compatible and socially efficient. For a power market of LQG agents, we show that there is a modified “Scaled” VCG (SVCG) mechanism that does satisfy incentive compatibility, social efficiency, budget balance, and individual rationality under a certain “market power balance” condition where no agent is too negligible or too dominant. We further show that the SVCG payments converge to the Lagrange payments, defined as the payments that correspond to the true price in the absence of strategic considerations, as the number of agents in the market increases. For LQ but non-Gaussian agents, optimal social welfare over the class of linear control laws is achieved.
Pinpointing the Massive Black Hole in the Galactic Center with Gravitationally Lensed Stars

A new statistical method for pinpointing the massive black hole (BH) in the Galactic center on the IR grid is presented and applied to astrometric IR observations of stars close to the BH. This is of interest for measuring the IR emission from the BH, in order to constrain accretion models; for solving the orbits of stars near the BH, in order to measure the BH mass and to search for general relativistic effects; and for detecting the fluctuations of the BH away from the dynamical center of the stellar cluster, in order to study the stellar potential. The BH lies on the line connecting the two images of any background source it gravitationally lenses, and so the intersection of these lines fixes its position. A joint search for a lensing signal and for the BH shows that the most likely point of intersection coincides with the center of acceleration of stars orbiting the BH. This statistical signal of lensing by the BH has a random probability of ~0.01. If true, it implies that there are a few distant supergiants behind the BH, while a simple mean Galactic model predicts none. This can be verified by deep IR stellar spectroscopy, which will determine whether the most likely lensed image pair candidates (listed here) have identical spectra.
Tools for CICYs in F-theory

We provide a set of tools for analyzing the geometry of elliptically fibered Calabi-Yau manifolds, starting with a description of the total space rather than with a Weierstrass model or a specified type of fiber/base. Such an approach to the subject of F-theory compactification makes certain geometric properties, which are usually hidden, manifest. Specifically, we review how to isolate genus-one fibrations in such geometries and then describe how to find their sections explicitly. This includes a full parameterization of the Mordell-Weil group where non-trivial. We then describe how to analyze the associated Weierstrass models, Jacobians and resolved geometries. We illustrate our discussion with concrete examples which are complete intersections in products of projective spaces (CICYs). The examples presented include cases exhibiting non-abelian symmetries and higher rank Mordell-Weil group. We also make some comments on non-flat fibrations in this context. In a companion paper [1] to this one, these results will be used to analyze the consequences for string dualities of the ubiquity of multiple fibrations in known constructions of Calabi-Yau manifolds.
SOFT X-RAY EXCESS OF CLUSTERS: A THERMAL FILAMENT MODEL AND THE STRONG LENSING OF BACKGROUND GALAXY GROUPS

The observational and theoretical status of the search for missing cosmological baryons is summarized, with a discussion of some indirect methods of detection. The thermal interpretation of the cluster soft X-ray and EUV excess phenomenon is examined in the context of emission filaments, which are the higher density part of the warm hot intergalactic medium (WHIM) residing at the outskirt of clusters. We derived an analytic radial profile of the soft excess surface brightness using a simple filament model, which provided us a means of observationally constraining the WHIM parameters, especially the total mass budget of warm gas associated with a cluster. We then pointed out a new scenario for soft excess emission, viz., a cluster that can strongly lens the soft X-rays from background WHIM knots. If, as seems quite likely, the missing baryons are mostly in the WHIM halos of galaxy groups, the lensing probability will be quite high (~10%). This way of accounting for at least part of a cluster's soft excess may also explain the absence of O VII absorption at the redshift of the cluster.
YANG–MILLS GRAVITY IN FLAT SPACE–TIME II: GRAVITATIONAL RADIATIONS AND LEE–YANG FORCE FOR ACCELERATED COSMIC EXPANSION

Within Yang–Mills gravity with translation group T(4) in flat space–time, the invariant action involving quadratic translation gauge-curvature leads to quadrupole radiations, which are shown to be consistent with experiments. The radiation power turns out to be the same as that in Einstein's gravity to the second-order approximation. We also discuss an interesting physical reason for the accelerated cosmic expansion based on the long-range Lee–Yang force of Ub(1) gauge field associated with the established conservation law of baryon number. We show that the Lee–Yang force can be related to a linear potential ∝ r, provided the gauge field satisfies a fourth-order differential equation in flat space–time. Furthermore, we consider an experimental test of the Lee–Yang force related to the accelerated cosmic expansion. The necessity of generalizing Lorentz transformations for accelerated frames of reference and accelerated Wu–Doppler effects are briefly discussed.
Improved Decay for Solutions to the Linear Wave Equation on a Schwarzschild Black Hole

We prove that sufficiently regular solutions to the wave equation \({\square_g\phi=0}\) on the exterior of the Schwarzschild black hole obey the estimates \({|\phi|\leq C_\delta v_+^{-\frac{3}{2}+\delta}}\) and \({|\partial_t\phi|\leq C_{\delta} v_+^{-2+\delta}}\) on a compact region of r, including inside the black hole region. This is proved with the help of a new vector field commutator that is analogous to the scaling vector field on Minkowski spacetime. This result improves the known decay rates in the region of finite r and along the event horizon.
Hadron Spectroscopy and Dynamics from Light-Front Holography and Superconformal Algebra

QCD is not supersymmetrical in the traditional sense—the QCD Lagrangian is based on quark and gluonic fields, not squarks nor gluinos. However, its hadronic eigensolutions conform to a representation of superconformal algebra, reflecting the underlying conformal symmetry of chiral QCD and its Pauli matrix representation. The eigensolutions of superconformal algebra provide a unified Regge spectroscopy of meson, baryon, and tetraquarks of the same parity and twist as equal-mass members of the same 4-plet representation with a universal Regge slope. The pion $$q \bar{q}$$ eigenstate has zero mass for $$m_q=0.$$ The superconformal relations also can be extended to heavy-light quark mesons and baryons. The combined approach of light-front holography and superconformal algebra also provides insight into the origin of the QCD mass scale and color confinement. A key observation is the remarkable dAFF principle which shows how a mass scale can appear in the Hamiltonian and the equations of motion while retaining the conformal symmetry of the action. When one applies the dAFF procedure to chiral QCD, a mass scale $$\kappa $$ appears which determines universal Regge slopes, hadron masses in the absence of the Higgs coupling, and the mass parameter underlying the Gaussian functional form of the nonperturbative QCD running coupling: $$\alpha _s(Q^2) \propto \exp {-{Q^2/4 \kappa ^2}}$$ , in agreement with the effective charge determined from measurements of the Bjorken sum rule. The mass scale $$\kappa $$ underlying hadron masses can be connected to the parameter $$\Lambda _{\overline{MS}}$$ in the QCD running coupling by matching its predicted nonperturbative form to the perturbative QCD regime. The result is an effective coupling $$\alpha _s(Q^2)$$ defined at all momenta. One also obtains empirically viable predictions for spacelike and timelike hadronic form factors, structure functions, distribution amplitudes, and transverse momentum distributions.
What if the Fast Radio Bursts 110220 and 140514 Are from the Same Source

The fast radio bursts (FRBs) 110220 and 140514 were detected at telescope pointing locations within 9 arcmin of each other over three years apart, both within the same 14.4 arcmin beam of the Parkes radio telescope. Nevertheless, they generally have not been considered to be from the same source because of a vastly different dispersion measure (DM) for the two bursts by over $380\,{\rm pc\,cm^{-3}}$. Here we consider the hypothesis that these two FRBs are from the same neutron star embedded within a supernova remnant (SNR) that provides an evolving DM as the ejecta expands and becomes more diffuse. Using such a model and the observed DM change, it can be argued that the corresponding SN must have occurred within $\approx10.2$ years of FRB 110220. Furthermore, constraints can be placed on the SN ejecta mass and explosion energy, which appear to require a stripped envelope (Type Ib/c) SN and/or a very energetic explosion. A third FRB from this location would be even more constraining, allowing the component of the DM due to the SNR to be separated from the unchanging DM components due to the host galaxy and intergalactic medium. In the future, if more FRBs are found to repeat, the sort of arguments presented here can be used to test the young neutron star progenitor hypothesis for FRBs.
Avoiding Help Avoidance: Using Interface Design Changes to Promote Unsolicited Hint Usage in an Intelligent Tutor

Within intelligent tutoring systems, considerable research has investigated hints, including how to generate data-driven hints, what hint content to present, and when to provide hints for optimal learning outcomes. However, less attention has been paid to how hints are presented. In this paper, we propose a new hint delivery mechanism called “Assertions” for providing unsolicited hints in a data-driven intelligent tutor. Assertions are partially-worked example steps designed to appear within a student workspace, and in the same format as student-derived steps, to show students a possible subgoal leading to the solution. We hypothesized that Assertions can help address the well-known hint avoidance problem. In systems that only provide hints upon request, hint avoidance results in students not receiving hints when they are needed. Our unsolicited Assertions do not seek to improve student help-seeking, but rather seek to ensure students receive the help they need. We contrast Assertions with Messages, text-based, unsolicited hints that appear after student inactivity. Our results show that Assertions significantly increase unsolicited hint usage compared to Messages. Further, they show a significant aptitude-treatment interaction between Assertions and prior proficiency, with Assertions leading students with low prior proficiency to generate shorter (more efficient) posttest solutions faster. We also present a clustering analysis that shows patterns of productive persistence among students with low prior knowledge when the tutor provides unsolicited help in the form of Assertions. Overall, this work provides encouraging evidence that hint presentation can significantly impact how students use them and using Assertions can be an effective way to address help avoidance.
Benchmarks of nonclassicality for qubit arrays

We present a set of practical benchmarks for N-qubit arrays that economically test the fidelity of achieving multi-qubit nonclassicality. The benchmarks are measurable correlators similar to two-qubit Bell correlators, and are derived from a particular set of geometric structures from the N-qubit Pauli group. These structures prove the Greenberger–Horne–Zeilinger (GHZ) theorem, while the derived correlators witness genuine N-partite entanglement and establish a tight lower bound on the fidelity of particular stabilizer state preparations. The correlators need only M ≤ N + 1 distinct measurement settings, as opposed to the 22N − 1 settings that would normally be required to tomographically verify their associated stabilizer states. We optimize the measurements of these correlators for a physical array of qubits that can be nearest-neighbor-coupled using a circuit of controlled-Z gates with constant gate depth to form N-qubit linear cluster states. We numerically simulate the provided circuits for a realistic scenario with N = 3, …, 9 qubits, using ranges of T1 energy relaxation times, T2 dephasing times, and controlled-Z gate-fidelities consistent with Google’s 9-qubit superconducting chip. The simulations verify the tightness of the fidelity bounds and witness nonclassicality for all nine qubits, while also showing ample room for improvement in chip performance.
KLT-type relations for QCD and bicolor amplitudes from color-factor symmetry

Color-factor symmetry is used to derive a KLT-type relation for tree-level QCD amplitudes containing gluons and an arbitrary number of massive or massless quark-antiquark pairs, generalizing the expression for Yang-Mills amplitudes originally postulated by Bern, De Freitas, and Wong. An explicit expression is given for all amplitudes with two or fewer quark-antiquark pairs in terms of the (modified) momentum kernel. We also introduce the bicolor scalar theory, the “zeroth copy” of QCD, containing massless biadjoint scalars and massive bifundamental scalars, generalizing the biadjoint scalar theory of Cachazo, He, and Yuan. We derive KLT-type relations for tree-level amplitudes of biadjoint and bicolor theories using the color-factor symmetry possessed by these theories.