ShantanuT01/DACTYL-Pretraining huggingface dataset:
We describe, in the context of M-theory on elliptically fibered Calabi-yau fourfolds, the change of variables that allow us to pass from the U(1) invariant elliptic fibration to the one describing the uncompactified four dimensional limit, where the U(1) symmetry is broken. These changes of variables are the analog to the ones used to derive from the Atiyah-Hitchin space the complex structure of the Seiberg-Witten solution for N=2 supersymmetric Yang-Mills. The connection between these changes of variables and the recently introduced rotation of branes is discussed.
The long-time behavior of the velocity autocorrelation function (VACF) is investigated by the molecular dynamics simulation of a two-dimensional system which has both a many-body interaction and a random potential. With strengthening the random potential by increasing the density of impurities, a crossover behavior of the VACF is observed from a positive tail, which is proportional to t^{-1}, to a negative tail, proportional to -t^{-2}. The latter tail exists even when the density of particles is the same order as the density of impurities. The behavior of the VACF in a nonequilibrium steady state is also studied. In the linear response regime the behavior is similar to that in the equilibrium state, whereas it changes drastically in the nonlinear response regime.
Starting from the gauge-invariant quark-antiquark Green function the expression for the nonrelativistic meson scattering amplitude is obtained and the nonperturbative form of this amplitude is discussed.
Full-shell nanowires (semiconducting nanowires fully coated with a superconducting shell) have been recently presented as a novel means to create Majorana zero modes. In contrast to partially coated nanowires, it has been argued that full-shell nanowires do not require high magnetic fields and low densities to reach a putative topological regime. Here we present a theoretical study of these devices taking into account all the basic ingredients, including a charge distribution spread across the section of the nanowire, required to qualitatively explain the first experimental results (Vaitiekenas et al., arXiv:1809.05513). We derive a criterion, dependent on the even-odd occupation of the radial subbands with zero angular momentum, for the appearance of Majorana zero modes. In the absence of angular subband mixing, these give rise to strong zero-bias anomalies in tunneling transport in roughly half of the system's parameter space under an odd number of flux quanta. Due to their coexistence with gapless subbands, the zero modes do not enjoy generic topological protection. Depending on the details of subband mixing in realistic devices, they can develop a topological minigap, acquire a finite lifetime or even be destroyed.
We try to single out some qualitative new effects of the coupling to the $\delta$-isovector-scalar meson introduced in a minimal way in a phenomenological hadronic field theory. Results for the equation of state ($EOS$) and the phase diagram of asymmetric nuclear matter ($ANM$) are discussed. We stress the consistency of the $\delta$-coupling introduction in a relativistic approach. New contributions to the slope and curvature of the symmetry energy and the neutron-proton effective mass splitting appear particularly interesting. A more repulsive $EOS$ for neutron matter at high baryon densities is expected. Effects on new critical properties of warm $ANM$, mixing of mechanical and chemical instabilities and isospin distillation, are also presented. The $\delta$ influence is mostly on the {\it isovectorlike} collective response.   The results are largely analytical and this makes the physical meaning quite transparent. Implications for nuclear structure properties of drip-line nuclei and for reaction dynamics with Radioactive Beams are finally pointed out.
In this paper, we study the Gevrey class regularity for solutions of the spatially homogeneous Landau equations in the hard potential case and the Maxwellian molecules case.
We extend to the strange quarks and antiquarks, the statistical approach of parton distributions and we calculate the strange quark asymmetry $s-\bar s$. We find that the asymmetry is small, positive in the low $x$ region and negative in the high $x$ region. In this framework, the polarized strange quarks and antiquarks distributions, which are obtained simultaneously, are found to be both negative for all $x$ values.
Dislocations play a key role in the understanding of many phenomena in solid state physics, materials science, crystallography and engineering. Dislocations are line defects producing distortions and self-stresses in an otherwise perfect crystal lattice. In particular, dislocations are the primary carrier of crystal plasticity and in dislocation based fracture mechanics.
n a number of papers it was shown that there are one-dimensional systems such that they contain solutions with, so called, overcompressive singular shock waves besides the usual elementary waves (shock and rarefaction ones as well as contact discontinuities). One can see their definition for a general 2 $\times$ 2 system with fluxes linear in one of dependent variables in \cite{Ned1}. This paper is devoted to examining their interactions with themselves and elementary waves. After a discussion of systems given in a general form, a complete analysis will be given for the ion-acoustic system.
In this note we study graphs $G_r$ with the property that every colouring of $E(G_r)$ with $r+1$ colours admits a copy of some graph $H$ using at most $r$ colours. For $1\le r\le e(H)$ such graphs occur naturally at intermediate steps in the synthesis of a $2$-colour Ramsey graph $G_1\longrightarrow H$. (The corresponding notion of Ramsey-type numbers was introduced by Erd\"os, Hajnal and Rado in 1965 and subsequently studied by Erd\"os and Szemer\'edi in 1972). For $H=K_n$ we prove a result on building a $G_{r}$ from a $G_{r+1}$ and establish Ramsey-infiniteness. From the structural point of view, we characterise the class of the minimal $G_r$ in the case when $H$ is relaxed to be the graph property of containing a cycle; we then use it to progress towards a constructive description of that class by proving both a reduction and an extension theorem.
The transport and thermodynamic properties of $\beta$-ReO$_{2}$ crystallizing in a nonsymmorphic structure were studied using high-quality single crystals. An extremely large magnetoresistance (XMR) reaching 22,000 $\%$ in a transverse magnetic field of 10 T at 2 K was observed. However, distinguished from other topological semimetals with low carrier densities that show XMR, $\beta$-ReO$_{2}$ has a high electron carrier density of 1 $\times$ $10^{22}$ cm$^{-3}$ as determined by Hall measurements and large Fermi surfaces in the electronic structure. In addition, a small Fermi surface with a small effective mass was evidenced by de Haas-van Alphen oscillation measurements. The previous band structure calculations [S. S. Wang, et al., Nat. Commun. 8, 1844 (2017)] showed that two kinds of loops made of Dirac points of hourglass-shaped dispersions exist and are connected to each other by a point to form a string of alternating loops, called the Dirac loop chain (DLC), which are protected by the multiple glide symmetries. Our first-principles calculations revealed the complex Fermi surfaces with the smallest one corresponding to the observed small Fermi surface, which is just located near the DLC. The XMR of $\beta$-ReO$_{2}$ is attributed to the small Fermi surface and thus is likely caused by the DLC.
The effect of Ge substitution on the magnetization, heat capacity, magnetocaloric effect and magnetoresistance of GdMn2Si2-xGex (x=0, 1, and 2) compounds has been studied. The magnetic transition associated with the Gd ordering is found to change from second order to first order on Ge substitution. Magnetic contributions to the total heat capacity and the entropy have been estimated. Magnetocaloric effect has been calculated in terms of adiabatic temperature change (deltaTad) as well as isothermal magnetic entropy change (deltaSM) using the heat capacity data. The temperature dependence of the magnetocaloric effect in all the three compounds have shown broad peaks. The maximum values of deltaSM and deltaTad for GdMn2Ge2 are found to be 5.9 J/kgK and 1.2 K, respectively. The magnetoresistance is found to be very large and positive with a maximum value of about 22% in the case of GdMn2Ge2. In the other two compounds also, the magnetoresistance is predominantly positive, except in the vicinity of the Gd ordering temperature. The anomalous nature of the magnetocaloric effect and the magnetoresistance has been attributed to the canted magnetic structure of these compounds.
In the present work, we investigate the formation of Stokes profiles and spectro-polarimetric diagnostics in an active region plage near the limb. We use 3-D radiation-MHD simulations with unipolar fields of an average strength of 400 G, which is largely concentrated in flux tubes in which the field reaches typical kilo-Gauss values. We generate synthetic Stokes spectra by radiative transfer calculations, then we degrade the simulated Stokes signal to account for observational conditions. The synthetic data treated in this manner are compared with and found to roughly reproduce spectro-polarimetric high-resolution observations at Mu=0.39 obtained by the SOUP instrument with the Swedish 1-m Solar Telescope at the beginning of 2006.
We study geometric aspects of extensions of the supersymmetric standard model that exhibit a periodic duality cascade. Via the holographic correspondence, the growth of the gauge group rank towards the UV is interpreted as a gradual decompactification transition. We show that this class of models typically develop a duality wall in the UV, and present an efficient method for estimating the hierarchy between the on-set of the cascade and the formation of the wall. As an illustrative example, we study the model introduced by Cascales, Saad and Uranga in [14], which has an known geometric realization in terms of D-branes on an SPP/Z_3 singularity.
Because of its key role in feedback in star formation and galaxy formation, we examine the nature of the interaction of a flow with discrete sources of mass injection. We show the results of two-dimensional numerical simulations in which we explore a range of configurations for the mass sources and study the effects of their proximity on the downstream flow. The mass sources act effectively as a single source of mass injection if they are so close together that the ratio of their combined mass injection rate is comparable to or exceeds the mass flux of the incident flow into the volume that they occupy. The simulations are relevant to many diffuse sources, such as planetary nebulae and starburst superwinds, in which a global flow interacts with material evaporating or being ablated from the surface of globules of cool, dense gas.
Weak heating events are frequent and ubiquitous in solar corona. They derive their energy from the local magnetic field and form a major source of local heating, signatures of which are seen in EUV and X-ray bands. Their radio emission arise from various plasma instabilities that lead to coherent radiation, making even a weak flare appear very bright. The radio observations hence probe non-equilibrium dynamics providing complementary information on plasma evolution. However, a robust study of radio emission from a weak event among many simultaneous events, requires high dynamic range imaging at sub-second andsub-MHz resolutions owing to their high spectro-temporal variability. Such observations were not possible until recently.This is among the first spatially resolved studies of an active region loop hosting a transient brightening (ARTB) and dynamically linked to a metrewave type-I noise storm. It uses imaging observations at metrewave, EUV and X-ray bands, along with magnetogram data. We believe this is the first spectroscopic radio imaging study of a type-I source, the data for which was obtained using the Murchison Widefield Array. We report the discovery of 30 s quasi-periodic oscillations (QPOs) in the radio light curve, riding on a coherent baseline flux. The strength of the QPOs and the baseline flux enhanced during a mircoflare associated with the ARTB. Our observations suggest a scenario where magnetic stress builds up over an Alfv\'{e}n timescale (30s) across the typical magnetic field braiding scale and then dissipates via a cascade of weak reconnection events.
We study the boundary regularity of solutions of the Dirichlet problem for the nonlocal operator with a kernel of variable orders. Since the order of differentiability of the kernel is not represented by a single number, we consider the generalized H\"older space. We prove that there exists a unique viscosity solution of $Lu = f$ in $D$, $u=0$ in $\mathbb{R}^n \setminus D$, where $D$ is a bounded $C^{1,1}$ open set, and that the solution $u$ satisfies $u \in C^V(D)$ and $u/V(d_D) \in C^\alpha (D)$ with the uniform estimates, where $V$ is the renewal function and $d_D(x) = \mbox{dist}(x, \partial D)$.
The anisotropy of magnetic properties commonly is introduced in textbooks using the case of an antiferromagnetic system with Ising type anisotropy. This model presents huge anisotropic magnetization and a pronounced metamagnetic transition and is well-known and well-documented both, in experiments and theory. In contrast, the case of an antiferromagnetic $X$-$Y$ system with weak in-plane anisotropy is only poorly documented. We studied the anisotropic magnetization of the compound GdRh$_2$Si$_2$ and found that it is a perfect model system for such a weak-anisotropy setting because the Gd$^{3+}$ ions in GdRh$_2$Si$_2$ have a pure spin moment of S=7/2 which orders in a simple AFM structure with ${\bf Q} = (001)$. We observed experimentally in $M(B)$ a continuous spin-flop transition and domain effects for field applied along the $[100]$- and the $[110]$-direction, respectively. We applied a mean field model for the free energy to describe our data and combine it with an Ising chain model to account for domain effects. Our calculations reproduce the experimental data very well. In addition, we performed magnetic X-ray scattering and X-ray magnetic circular dichroism measurements, which confirm the AFM propagation vector to be ${\bf Q} = (001)$ and indicate the absence of polarization on the rhodium atoms.
The LEP experiments give a lower bound on the neutralino mass of about 46 GeV which, however, relies on a supersymmetric grand unification relation. Dropping this assumption, the experimental lower bound on the neutralino mass vanishes completely. Recent analyses suggest, however, that in the minimal supersymmetric standard model (MSSM), a light neutralino dark matter candidate has a lower bound on its mass of about 7 GeV. In light of this, we investigate the mass sensitivity at the ILC for very light neutralinos. We study slepton pair production, followed by the decay of the sleptons to a lepton and the lightest neutralino. We find that the mass measurement accuracy for a few-GeV neutralino is around 2 GeV, or even less if the relevant slepton is sufficiently light. We thus conclude that the ILC can help verify or falsify the MSSM neutralino cold dark matter model even for very light neutralinos.
Comments on NC Abelian Higgs model withdrawn. An improved treatment of NC U(2) adjoint models to appear elsewhere.
We study the signal in the Cosmic Microwave Background (CMB) polarization anisotropy resulting from patchy reionization. It is well known that the primordial polarization of the CMB is very sensitive to the details of reionization. Combining a semi-analytic model of galaxy formation, in which the optical depth to the reionization epoch is in the range 0.014 to 0.048, with a high resolution N-body simulation we find that reionization generates a peak with amplitude 0.05~0.15 \mu K at large angular scales. The position of this peak reveals the size of the horizon at reionization, whilst its amplitude is a measure of the optical depth to reionization. On small scales, ionized patches prior to full reionization create a second order polarization signal due to the coupling of the free electron density fluctuation with the quadrupole moment of the temperature anisotropy. Careful study reveals that the coupling generates the same power spectra for electric and magnetic modes, whose amplitudes of polarization anisotropies from this process are predicted to be ~10nK. The amplitude depends strongly on the total baryon density $\Omega_b$ and on the spatial correlations of the free electron density in the ionized regions, and weakly on the fraction of ionizing photons able to escape their source galaxy, $f_{esc}$. The first- and second-order signals are therefore sensitive to the details of how the reionization occurred. Detection of these signals will place important constraints on the reionization history of the Universe.
We use the non-equilibrium bosonization technique to investigate effects of the Coulomb interaction on quantum Hall edge states at filing factor nu=2, partitioned by a quantum point contact (QPC). We find, that due to the integrability of charge dynamics, edge states evolve to a non-equilibrium stationary state with a number of specific features. In particular, the noise temperature of a weak backscattering current between edge channels is linear in voltage bias applied at the QPC, independently of the interaction strength. In addition, it is a non-analytical function of the QPC transparency T and scales as Tln(1/T) at T<< 1. Our predictions are confirmed by exact numerical calculations.
We study the effect of the cosmological constant on the statistical properties of gravitational lenses in flat cosmologies (Omega_{0}+lambda_{0} = 1). It is shown that some of the lens observables are strongly affected by the cosmological constant, especially in a low--density universe, and its existence might be inferred by a statistical study of the lenses. In particular, the optical depth of the lens distribution may be used best for this purpose without depending much on the lens model. We calculate the optical depth (probabilty of a beam encountering with a lens event) for a source in a new picture of galaxy evolution based on number evolution in addition to pure luminosity evolution. It seems that present day galaxies result from the merging of a large number of building blocks. We have tried to put limit on the cosmological constant in this new picture of galaxy evolution. This evolutionary model of galaxies permits larger value of cosmological constant.
We have reanalyzed reaction cross sections of 16N on 12C target. The nucleon density distribution of 16N, especially surface density distribution, was extracted using the modified Glauber model. On the basis of dilute surface densities, the discussion of 15N(n, {\gamma})16N reaction was performed within the framework of the direct capture reaction mechanism. The calculations agreed quite well with the experimental data.
Circulant graphs have been used to effectively establish lower bounds on many classical Ramsey numbers. Here, we construct circulant graphs of prime order that sharpen the best published lower bounds on two Ramsey numbers. Generalizing previous work in which quadratic and cubic residues were used to construct circulant graphs for the same purpose, we report on the use of quartic and higher-order residues.
We present the first polarization measurements of the radio emission from RRAT J1819$-$1458. Our observations, conducted in parallel to regular timing sessions, have yielded a small number of bright and polarized pulses. The polarization characteristics and integrated profile resemble those of normal pulsars with average spin-down energy (Edot): moderate to low linear polarization in the integrated profile despite relatively high polarization in the individual pulses. On average, a small degree of circular polarization is also observed. The polarization position angle executes a remarkably smooth, steep S-shaped curve, interrupted by two orthogonal jumps. Based on the shape of the PA swing, we place some constraints on the emission geometry. We compare these polarization properties to those of other radio emitting neutron star populations, including young pulsars, pulsars with a high surface magnetic field and radio emitting magnetars. From the polarization measurements, the Faraday rotation measure of this RRAT is derived.
Determination of the expansion and acceleration history of the universe is one of the fundamental goals of cosmology. Detailed measurements of these rates as a function of redshift can provide new physical insights into the nature and evolution of the dark energy, which apparently dominates the global dynamics of the universe at the present epoch. We present here dimensionless coordinate distances y(z) to twenty radio galaxies reaching out to z of about 1.8, the redshift range currently not covered by Supernova standard candle observations. We develop a simple numerical method for a direct determination of the expansion and acceleration rates, E(z) and q(z), from the data, which makes no assumptions about the underlying cosmological model or the equation of state parameter w. This differential method is in contrast to the traditional cosmological tests, where particular model equations are integrated and then compared with the observations. The new model-independent method is applied to currently available Supernova data and the data on radio galaxies presented here. We derive the expansion rate of the universe as a function of redshift, E(z), and for the first time obtain a direct estimate of the acceleration rate of the universe as a function of redshift, q(z), in a way that is independent of assumptions regarding the dark energy and its redshift evolution. The current observations indicate that the universe transitions from acceleration to deceleration at a redshift greater than 0.3, with a best fit estimate of about 0.45; this transition redshift and our determinations of E(z) are broadly in agreement with the currently popular Friedmann-Lemaitre cosmology with Omega = 0.3, and Lambda = 0.7, even though no model assumptions are made in deriving the fits for E(z) and q(z).
The magnetic moments of ${}^2{H}$, ${}^3{He}$ and ${}^3{H}$ as well as the thermal neutron capture rate on the proton are calculated using heavy baryon chiral perturbation theory {\it \`{a} la} Weinberg. The M1 operators have been derived up to {N$^3$LO}. The nuclear matrix elements are evaluated with the use of wave functions obtained by carrying out variational Monte Carlo calculations for a realistic nuclear Hamiltonian involving high-precision phenomenological potentials like Argonne Av18 and Urbana IX tri-nucleon interactions. We discuss the potential- and cutoff-dependence of the results.
The motivations for low-energy supersymmetry and the main features of the minimal supersymmetric extension of the Standard Model are reviewed. Possible non-minimal models and the issue of gauge coupling unification are also discussed. Theoretical results relevant for supersymmetric particle searches at present and future accelerators are presented, with emphasis on the role of a proposed $\epem$ collider with $\sqrt{s}   = 500 \gev$. In particular, recent results on radiative corrections to supersymmetric Higgs boson masses and couplings are summarized, and their implications for experimental searches are discussed in some detail. (Plenary talk at the Workshop on Physics and Experiments with Linear Colliders, Saariselk\"a, Lapland, Finland, 9--14 September 1991)