ShantanuT01/DACTYL-Pretraining huggingface dataset:
Starting from N=2 supersymmetric theories in 2 dimensions, we formulate a novel time-dependent supersymmetric quantum theory where the R-charge is twisted along the time. The invariance of the supersymmetric index under variations of the action for these theories leads to two predictions: In the IR limit it predicts how the degeneracy of BPS states change as we cross the walls of marginal stability. On the other hand, its equivalence with the UV limit relates this to the spectrum of the U(1) R-charges of the Ramond ground states at the conformal point. This leads to a conceptually simple derivation of results previously derived using tt* geometry, now based on time-dependent supersymmetric quantum mechanics.
We consider a mixture of passive (i.e., Brownian) and active (e.g., bacterial or colloidal swimmers) particles, and analyze the stability conditions of either uniformly mixed or phase segregated steady states consisting of phases enriched with different types of particles. We show that in sufficiently dilute mixtures the system behaves as if it were exposed to two separate heat baths of uneven temperatures. It can be described within a second virial approximation neglecting three body and higher order collisions. In this approximation, we define non-equilibrium "chemical potentials" whose gradients govern diffusion fluxes and a non-equilibrium "osmotic pressure", which governs the mechanical stability of the interface.
We consider a sequence of Leray-Hopf weak solutions of the 2D Navier-Stokes equations on a bounded domain, in the vanishing viscosity limit. We provide sufficient conditions on the associated vorticity measures, away from the boundary, which ensure that as the viscosity vanishes the sequence converges to a weak solution of the Euler equations. These assumptions are consistent with vortex sheet solutions of the Euler equations.
We present a new algorithm to identify fragments in computer simulations of relativistic heavy ion collisions. It is based on the simulated annealing technique and can be applied to n-body transport models like the Quantum Molecular Dynamics. This new approach is able to predict isotope yields as well as hyper-nucleus production. In order to illustrate its predicting power, we confront this new method to experimental data, and show the sensitivity on the parameters which govern the cluster formation.
We present a new special relativistic hydrodynamics (SRHD) code capable of handling coexisting ultra-relativistically hot and non-relativistically cold gases. We achieve this by designing a new algorithm for conversion between primitive and conserved variables in the SRHD solver, which incorporates a realistic ideal-gas equation of state covering both the relativistic and non-relativistic regimes. The code can handle problems involving a Lorentz factor as high as $10^6$ and optimally avoid the catastrophic cancellation. In addition, we have integrated this new SRHD solver into the code GAMER (https://github.com/gamer-project/gamer) to support adaptive mesh refinement and hybrid OpenMP/MPI/GPU parallelization. It achieves a peak performance of $7\times 10^{7}$ cell updates per second on a single Tesla P100 GPU and scales well to 2048 GPUs. We apply this code to two interesting astrophysical applications: (a) an asymmetric explosion source on the relativistic blast wave and (b) the flow acceleration and limb-brightening of relativistic jets.
The increase of a thermoelectric material's figure of merit (ZT value) is limited by the interplay of the transport coefficients. Here we report the greatly enhanced thermoelectric performance of a ZrS2 monolayer by the biaxial tensile strain, due to the simultaneous increase of the Seebeck coefficient and decrease of the thermal conductivity. Based on the first-principles calculations combined with the Boltzmann transport theory, we predict the band gap of the ZrS2 monolayer can be effectively engineered by the strain and the Seebeck coefficient is significantly increased. The thermal conductivity is reduced by the applied tensile strain due to the phonon softening. At the strain of 6%, the maximal ZT value of 2.4 is obtained for the p-type doped ZrS2 monolayer at 300 K, which is 4.3 times larger than that of the unstrained system.
In this thesis, we study a variety of phenomena in strongly coupled quantum field theories by performing calculations in their gravitational duals. We compute entanglement entropy in a variety of holographic systems, paying particular attention to its long-distance behaviour, characterised by a term proportional to surface area. This term is known to decrease along Lorentz-invariant renormalisation group flows, suggesting that it may count massless degrees of freedom. We find that more general deformations may increase this area term, possibly indicating an enhanced number of long-distance degrees of freedom. We observe a correlation between this enhancement and the emergence of new scaling symmetry at long distances. Next, we study the spectrum of collective excitations in a holographic model of a non-Fermi liquid. At high temperatures, the spectrum of collective excitations includes hydrodynamic sound waves. As in similar models, we observe that sound-like modes also exist at low temperatures. Such modes are known as holographic zero sound. We study the changing properties of holographic zero sound and the emergence of hydrodynamic behaviour at high temperatures as we vary the parameters of the model. We find that for certain values of the parameters, the temperature-dependence of holographic zero sound qualitatively resembles that of a normal Fermi liquid. Finally, we study the entanglement entropy contribution of surface defects in a six-dimensional quantum field theory of relevance to M-theory, which is a candidate theory of quantum gravity. We find that the entanglement entropy does not montonically decrease along renormalisation group flows on these defects, ruling it out as a potential measure of degrees of freedom. On the other hand, we find that two of the contributions of the defect to the Weyl anomaly of the quantum field theory decrease along all of the flows that we study.
Isoscalar and isovector particle densities are derived analytically by using the approximation of a sharp edged nucleus within the local energy density approach with the proton-neutron asymmetry and spin-orbit effects. Equations for the effective nuclear-surface shapes as collective variables are derived up to the higher order corrections in the form of the macroscopic boundary conditions. The analytical expressions for the isoscalar and isovector tension coefficients of the nuclear surface binding energy and the finite-size corrections to the $\beta $ stability line are obtained.
Asteroseismology involves probing the interiors of stars and quantifying their global properties, such as radius and age, through observationsof normal modes of oscillation. The technical requirements for conducting asteroseismology include ultra-high precision measured in photometry in parts per million, as well as nearly continuous time series over weeks to years, and cadences rapid enough to sample oscillations with periods as shortas a few minutes. We report on results from the first 43 days of observations in which the unique capabilities of Kepler in providing a revolutionary advance in asteroseismology are already well in evidence. The Kepler asteroseismology program holds intrinsic importance in supporting the core planetary search program through greatly enhanced knowledge of host star properties, and extends well beyond this to rich applications in stellar astrophysics.
We consider the region $\mathscr{T}$ in spacetime containing future-trapped closed surfaces and its boundary $\B$, and derive some of their general properties. We then concentrate on the case of spherical symmetry, but the methods we use are general and applicable to other situations. We argue that closed trapped surfaces have a non-local property, "clairvoyance", which is inherited by $\B$. We prove that $\B$ is not a marginally trapped tube in general, and that it can have portions in regions whose whole past is flat. For asymptotically flat black holes, we identify a general past barrier, well inside the event horizon, to the location of $\B$ under physically reasonable conditions. We also define the core $\mathscr{Z}$ of the trapped region as that part of $\mathscr{T}$ which is indispensable to sustain closed trapped surfaces. We prove that the unique spherically symmetric dynamical horizon is the boundary of such a core, and we argue that this may serve to single it out. To illustrate the results, some explicit examples are discussed, namely Robertson-Walker geometries and the imploding Vaidya spacetime.
In this paper, a new video super-resolution reconstruction (SRR) method with improved robustness to outliers is proposed. Although the R-LMS is one of the SRR algorithms with the best reconstruction quality for its computational cost, and is naturally robust to registration inaccuracies, its performance is known to degrade severely in the presence of innovation outliers. By studying the proximal point cost function representation of the R-LMS iterative equation, a better understanding of its performance under different situations is attained. Using statistical properties of typical innovation outliers, a new cost function is then proposed and two new algorithms are derived, which present improved robustness to outliers while maintaining computational costs comparable to that of R-LMS. Monte Carlo simulation results illustrate that the proposed method outperforms the traditional and regularized versions of LMS, and is competitive with state-of-the-art SRR methods at a much smaller computational cost.
We present direct evidence of above room temperature magneto-electricity in single-phase Li0.05Ti0.02Ni0.93O with above-ambient antiferromagnetic ordering. Temperature-hysteresis in warming/cooling heat-flow thermograms establishes a discontinuous/first-order nature of the cubic-to-rhombohedral structural change concurring the AFM transition. At TN = 488K, magnetization features a sharp slope-&-curvature discontinuity and dielectric constant shows a peak-anomaly. Room temperature P-E loop measures a large polarization traceable to the N\`eel domain walls. We find positive room-temperature magneto-capacitance up to 9T, linear at low-fields (MC ~ Hlow); the prefactor slope (dln{\epsilon}'/dHlow) featuring a positive frequency-coefficient rises from O(10-3/T) at 0.1MHz to O(10-1/T) at 4MHz, with maximum d{\epsilon}'/dH ~ 120/T.
The $^{66}$Ge and $^{68}$Ge nuclei are studied by means of the shell model with the extended $P+QQ$ Hamiltonian, which succeeds in reproducing experimentally observed energy levels, moments of inertia and other properties. The investigation using the reliable wave-functions predicts T=0, J=9 one-proton-one-neutron ($1p1n$) alignment in the $g_{9/2}$ orbit, at high spins ($14_1^+$, $16_1^+$ and $18_1^+$) in these $N \approx Z$ even-even nuclei. It is shown that a series of the even-$J$ positive-parity yrast states (observed up to $26_1^+$ for $^{68}$Ge) consists of the ground-state band and successive three bands with different types of particle alignments (two-neutron, $1p1n$, two-proton-two-neutron) in the $g_{9/2}$ orbit.
Theoretically core-multishell nanowires under a cross-section of hexagonal geometry should exhibit peculiar confinement effects. Using a hard X-ray nanobeam, here we show experimental evidence for carrier localization phenomena at the hexagon corners by combining synchrotron excited optical luminescence with simultaneous X-ray fluorescence spectroscopy. Applied to single coaxial n-GaN/InGaN multiquantum-well/p-GaN nanowires, our experiment narrows the gap between optical microscopy and high-resolution X-ray imaging, and calls for further studies on the underlying mechanisms of optoelectronic nanodevices.
We introduce a modular (integral) complementary polynomial $\kappa(G;x,y)$ ($\kappa_{\mathbbm z}(G;x,y)$) of two variables of a graph $G$ by counting the number of modular (integral) complementary tension-flows (CTF) of $G$ with an orientation $\epsilon$. We study these polynomials by further introducing a cut-Eulerian equivalence relation on orientations and geometric structures such as the complementary open lattice polyhedron $\Delta_\textsc{ctf}(G,\epsilon)$, the complementary open 0-1 polytope $\Delta^+_\textsc{ctf}(G,\epsilon)$, and the complementary open lattice polytopes $\Delta^\rho_\textsc{ctf}(G,\epsilon)$ with respect to orientations $\rho$. The polynomial $\kappa(G;x,y)$ ($\kappa_{\mathbbm z}(G;x,y)$) is a common generalization of the modular (integral) tension polynomial $\tau(G,x)$ ($\tau_\mathbbm{z}(G,x)$) and the modular (integral) flow polynomial $\phi(G,y)$ ($\phi_\mathbbm{z}(G,y)$), and can be decomposed into a sum of product Ehrhart polynomials of complementary open 0-1 polytopes $\Delta^+_\textsc{ctf}(G,\rho)$. There are dual complementary polynomials $\bar\kappa(G;x,y)$ and $\bar\kappa_{\mathbbm z}(G;x,y)$, dual to $\kappa$ and $\kappa_{\mathbbm z}$ respectively, in the sense that the lattice-point counting to the Ehrhart polynomials is taken inside a topological sum of the dilated closed polytopes $\bar\Delta^+_\textsc{ctf}(G,\rho)$. It turns out that the polynomial $\bar\kappa(G;x,y)$ is Whitney's rank generating polynomial $R_G(x,y)$, which gives rise to a combinatorial interpretation on the values of the Tutte polynomial $T_G(x,y)$ at positive integers. In particular, some special values of $\kappa_\mathbbm{z}$ and $\bar\kappa_\mathbbm{z}$ ($\kappa$ and $\bar\kappa$) count the number of certain special kinds (of equivalence classes) of orientations.
The Mott transition in a two-band Hubbard model involving subbands of different widths is studied as a function of temperature using dynamical mean field theory combined with exact diagonalization. The phase diagram is shown to exhibit two successive first-order transitions if the full Hund's rule coupling is included. In the absence of spin-flip and pair-exchange terms the lower transition remains first-order while the upper becomes continuous.
NGC 7129 FIRS 2 is a young intermediate-mass (IM) protostar, which is associated with two energetic bipolar outflows and displays clear signs of the presence of a hot core. It has been extensively observed with ground based telescopes and within the WISH Guaranteed Time Herschel Key Program. We present new observations of the C18O 3-2 and the HDO 3_{12}-2_{21} lines towards NGC 7129 FIRS 2. Combining these observations with Herschel data and modeling their emissions, we constrain the C18O and HDO abundance profiles across the protostellar envelope. In particular, we derive the abundance of C18O and HDO in the hot core. The intensities of the C18O lines are well reproduced assuming that the C18O abundance decreases through the protostellar envelope from the outer edge towards the centre until the point where the gas and dust reach the CO evaporation temperature (~20-25 K) where the C18O is released back to the gas phase. Once the C18O is released to the gas phase, the modelled C18O abundance is found to be ~1.6x10^{-8}, which is a factor of 10 lower than the reference abundance. This result is supported by the non-detection of C18O 9-8, which proves that even in the hot core (T_k>100 K) the CO abundance must be 10 times lower than the reference value. Several scenarios are discussed to explain this C18O deficiency. One possible explanation is that during the pre-stellar and protostellar phase, the CO is removed from the grain mantles by reactions to form more complex molecules. Our HDO modeling shows that the emission of HDO 3_{12}-2_{21} line is maser and comes from the hot core (T_k>100 K). Assuming the physical structure derived by Crimier et al. (2010), we determine a HDO abundance of ~0.4 - 1x10^{-7} in the hot core of this IM protostar, similar to that found in the hot corinos NGC 1333 IRAS 2A and IRAS 16293-2422.
Information-theory based variational principles have proven effective at providing scalable uncertainty quantification (i.e. robustness) bounds for quantities of interest in the presence of nonparametric model-form uncertainty. In this work, we combine such variational formulas with functional inequalities (Poincar{\'e}, $\log$-Sobolev, Liapunov functions) to derive explicit uncertainty quantification bounds for time-averaged observables, comparing a Markov process to a second (not necessarily Markov) process. These bounds are well-behaved in the infinite-time limit and apply to steady-states of both discrete and continuous-time Markov processes.
Dilepton production in In+In collisions at 158 AGeV is studied within the microscopic Parton-Hadron-Strings Dynamics (PHSD) transport approach, which is based on a dynamical quasiparticle model (DQPM) matched to reproduce lattice QCD results in thermodynamic equilibrium. A comparison to the data of the NA60 Collaboration shows that the low mass dilepton spectra are well described by including a collisional broadening of vector mesons, while the spectra in the intermediate mass range are dominated by off-shell quark-antiquark annihilation in the nonperturbative QGP. In particular, the observed softening of the mT spectra at intermediate masses is reproduced.
We generalize methods to compute various kinds of rank to the case of a toric variety $X$ embedded into projective space using a very ample line bundle $\mathcal{L}$. We find an upper bound on the cactus rank. We use this to compute rank, border rank, and cactus rank of monomials in $H^0(X,\mathcal{L})^*$ when $X$ is $\mathbb{P}^1 \times \mathbb{P}^1$, the Hirzebruch surface $\mathbb{F}_1$, the weighted projective plane $\mathbb{P}(1,1,4)$, or a fake weighted projective plane.
We extend the study of the effect of static primordial black holes on vacuum decay. In particular, we compare the tunneling rates between vacua of different values of the cosmological constant and black hole mass by pointing out the dominant processes based on a numerical examination of the thin wall instanton. Three distinct cases are considered, namely the nucleation of a true vacuum bubble into the false vacuum, the nucleation of a false vacuum bubble into the true vacuum as well as the Farhi-Guth-Guven mechanism. As a proof of concept, it is shown that in order to increase the transition rate into an inflating region, we find that not only is the inclusion of a black hole necessary, but the inclusion of a cosmological constant in the initial phase is also required. Among the cases studied, we show that the most likely scenario is the elimination of inhomogeneities in the final phase.
The spurious states found in numerical implementations of envelope function models for semiconductor heterostructures and nanostructures are artifacts of the use of the centered-difference formula. They are readily removed by employing a first-order difference scheme. The technique produces none of the loss of accuracy that is commonly feared from lower-order formulations; the fidelity to the continuum band structure is actually improved. Moreover the stability is absolute, thus no adjustments to the model parameters are required. These properties are demonstrated in an explicit calculation of a 3-band model of a semiconductor superlattice.
We present calculations of spin-dependent electron transport through single organic molecules bridging pairs of iron nanocontacts. We predict the magnetoresistance of these systems to switch from positive to negative with increasing applied bias for both conducting and insulating molecules. This novel inverse magnetoresistance phenomenon is robust, does not depend on the presence of impurities, and is unique to molecular and atomic nanoscale magnetic junctions. Its physical origin is identified and its relevance to experiment and to potential technological applications is discussed.
The paper deals with an extremal problem concerning colorings of hypergraphs with bounded edge degrees. Consider the family of $b$-simple hypergraphs, in which any two edges do not share more than $b$ common vertices. We prove that for $n\geqslant n_0(b)$, any $n$-uniform $b$-simple hypergraph with the maximum edge degree at most $c\cdot nr^{n-b}$ is $r$-colorable, where $c>0$ is an absolute constant. We also establish some applications of the main result.
We report magnetization and differential thermal analysis measurements as a function of pressure accross the martensitic transition in magnetically superelastic Ni-Mn-In alloys. It is found that the properties of the martensitic transformation are significantly affected by the application of pressure. All transition temperatures shift to higher values with increasing pressure. The largest rate of temperature shift with pressure has been found for Ni$_{50}$Mn$_{34}$In$_{16}$ as a consequence of its small entropy change at the transition. Such a strong pressure dependence of the transition temperature opens up the possibility of inducing the martensitic transition by applying relatively low hydrostatic pressures.
Substitution of nickel by copper in the heavy fermion system CeNi$_{9-x}$Cu$_x$Ge$_4$ alters the local crystal field environment of the Ce$^{3+}$-ions. This leads to a quantum phase transition near $x\approx0.4$, which is not only driven by the competition between Kondo effect and RKKY interaction, but also by a reduction of an effectively fourfold to a twofold degenerate crystal field ground state. To study the consequences of a changing crystal field in CeNi$_8$CuGe$_4$ on its Kondo properties, inelastic neutron scattering (INS) experiments were performed. Two well-defined crystal field transitions were observed in the energy-loss spectra at 4 K. The crystal field level scheme determined by neutron spectroscopy is compared with results from specific heat measurements.
We examine electronic transport in a spin-blockaded double quantum dot. We show that by tuning the strength of the spin-orbit interaction the current flowing through the double dot exhibits a dip at zero magnetic field or a peak at a magnetic field for which the two-electron energy levels anticross. This behaviour is due to the dependence of the singlet-triplet mixing on the field and spin-orbit amplitude. We derive approximate expressions for the current as a function of the amplitudes of the states involved in the transport. We also consider an alternative model that takes into account a finite number of nuclear spins and study the resulting coupled dynamics between electron and nuclear spins. We show that if the spin ensemble is in a thermal state there are regular oscillations in the transient current followed by quasi-chaotic revivals akin to those seen in a thermal Jaynes-Cummings model.