ShantanuT01/DACTYL-Pretraining huggingface dataset:
The spin 1/2 XXZ chain in a random magnetic field pointing in the Z direction is numerically studied using the Density Matrix Renormalization Group (DMRG) method. The phase diagram as a function of the anisotropy of the XXZ Hamiltonian and the strength of the random field is analyzed by computing the spin correlations and the superfluid density. To obtain the superfluid density we consider a superblock configuration representing a closed system with an arbitrary twist at the boundary. This allows us to estimate the size of the critical region where the quasi-long-range order persists, that is, where the spin correlation length is infinite and the superfluid density is non-zero.
Prudent walks are self-avoiding walks on the square lattice which never step into the direction of an already occupied vertex. We study the closed version of these walks, called prudent polygons, where the last vertex is adjacent to the first one. More precisely, we give the half-perimeter generating functions of two subclasses of prudent polygons, which turn out to be algebraic and non-D-finite, respectively.
We prove the uniqueness of bounded solutions for the spatially homogeneous Fokker-Planck-Landau equation with a Coulomb potential. Since the local (in time) existence of such solutions has been proved by Arsen'ev-Peskov (1977), we deduce a local well-posedness result. The stability with respect to the initial condition is also checked.
Based on the first-principles plane wave calculations, we showed that Ca adsorbed on graphene can serve as a high-capacity hydrogen storage medium, which can be recycled by operations at room temperature. Ca is chemisorbed by donating part of its 4s-charge to the empty $\pi^*$-band of graphene. At the end adsorbed Ca atom becomes positively charged and the semi-metallic graphene change into a metallic state. While each of adsorbed Ca atoms forming the (4x4) pattern on the graphene can absorb up to five H_2 molecules, hydrogen storage capacity can be increased to 8.4 wt % by adsorbing Ca to both sides of graphene and by increasing the coverage to form the (2x2) pattern. Clustering of Ca atoms is hindered by the repulsive Coulomb interaction between charged Ca atoms.
Over the last 25 years Monte Carlo programs were being developped in Cracow in the group guided by Prof. Stanislaw Jadach. Many of those programs became standard in their application domains. In the following let us review some aspects of such projects which were probably at the foundation of their success. We will concentrate on mathematical aspects of their design and history of their construction. It is rather difficult to cover 25 years of the research in a single talk. That is why, I have organized my presentation around Monte Carlo PHOTOS but stressing its relation to other activities and projects often realized together with Prof. Jadach. Many of omitted aspects will find their way into other perentations collected in this volume.   I will concentrate on issues related to phasespace parametrization and spin amplitudes as used in our Monte Carlo programs such as MUSTRAAL, TAUOLA or KKMC and their similarities and differences with respect to solution used in PHOTOS.
Deep H$\alpha$ images of a sample of nearby late-type spiral galaxies have been analyzed to characterize the morphology and energetic significance of the ``Diffuse Ionized Medium'' (DIM). We find that the DIM properties can be reasonably unified as a function of relative surface brightness, by using a new method to quantify the DIM importance in galaxies. This new approach is more consistent with the fundamentally morphological definition of the DIM as being `Diffuse', compared to the traditional way adopted in previous studies that could only isolate the DIM based on an absolute surface brightness criterion. Our results suggest that the variation of the DIM's significance among the galaxies is small enough so that the fractional contribution of the DIM to the global H$\alpha$ luminosity in the galaxies is fairly constant, as has been observed. We found a smooth structural transition from HII regions to the DIM, suggesting that the ionizing energy for the DIM mainly comes from HII regions.
The experimental STM images for the CDW phase of the blue bronze RbMoO3 have been successfully explained on the basis of first-principles DFT calculations. Although the density of states near the Fermi level strongly concentrates in two of the three types of Mo atoms Mo-II and Mo-III, the STM measurement mostly probes the contribution of the uppermost O atoms of the surface, associated with the Mo-IO6 octahedra. In addition, it is found that the surface concentration of Rb atoms plays a key role in determining the surface nesting vector and hence the periodicity of the CDW modulation. Significant experimental inhomogeneities of the b* surface component of the wavevector of the modulation, probed by STM, are reported. The calculated changes in the surface nesting vector are consistent with the observed experimental inhomogeneities.
In the investigation of the evolution of cosmological perturbations in inflationary universe models the behavior of perturbations during the reheating stage is the most unclear point. In particular in the early reheating phase in which a rapidly oscillating scalar field dominates the energy density, the behavior of perturbations are not known well because their evolution equation expressed in terms of the curvature perturbation becomes singular. In this paper it is shown that in spite of this singular behavior of the evolution equation the Bardeen parameter stays constant in a good accuracy during this stage for superhorizon-scale perturbations except for a sequence of negligibly short intervals around the zero points of the time derivative of the scalar field. This justifies the conventional formula relating the amplitudes of quantum fluctuations during inflation and those of adiabatic perturbations at horizon crossing in the Friedmann stage, except for possible corrections produced by the energy transfer from the scalar field to radiation in the late stage of reheating. It is further shown that outside the above sequence of time intervals the behavior of the perturbations coincides in a good accuracy with that for a perfect fluid system obtained from the original scalar field system by the WKB approximation and a spacetime averaging over a Hubble horizon scale.
The ferromagnetic to nonferromagnetic (α-β) phase transition in epitaxial MnAs layers on GaAs(100) is studied by x-ray magnetic circular dichroism and x-ray magnetic linear dichroism photoemission electron microscopy in order to elucidate the nature of the controversial nonferromagnetic state of β-MnAs. In the coexistence region of the two phases the β phase shows a clear XMLD signal characteristic of antiferromagnetism. The nature and the possible causes of the elusiveness of this magnetic state are discussed.
The collision of Deep Impact with comet 9P/Tempel 1 generated a bright cloud of dust which dissipated during several days after the impact. The brightness variations of this cloud and the changes of its position and shape are governed by the physical properties of the dust grains. We use a Monte Carlo model to describe the evolution of the post-impact dust plume. The results of our dynamical simulations are compared to the data obtained with FORS2, the FOcal Reducer and low dispersion Spectrograph for the VLT of the European Southern Observatory (ESO), to derive the particle size distribution and the total amount of material contained in the dust ejecta cloud.
In this thesis, following F. Brown's point of view, we look at the Hopf algebra structure of motivic cyclotomic multiple zeta values, which are motivic periods of the fundamental groupoid of $\mathbb{P}^{1} \diagdown \lbrace 0, \mu_{N}, \infty \rbrace $. By application of a surjective \textit{period} map (which, under Grothendieck's period conjecture, is an isomorphism), we deduce results (such as generating families, identities, etc.) on cyclotomic multiple zeta values, which are complex numbers. The coaction of this Hopf algebra (explicitly given by a combinatorial formula from A. Goncharov and F. Brown's works) is the dual of the action of a so-called \textit{motivic} Galois group on these specific motivic periods. This entire study was actually motivated by the hope of a Galois theory for periods, which should extend the usual Galois theory for algebraic numbers.
Our magnetotransport measurements of quantum Hall stripes in a high-quality GaAs quantum well in a slightly tilted magnetic field reveal that the orientation of stripes can be changed by temperature. Field-cooling and field-warming measurements, as well as observation of hysteresis at intermediate temperatures allow us to conclude that the observed temperature-induced reorientation of stripes is owing to the existence of two distinct minima in the symmetry-breaking potential. We also find that the native symmetry-breaking mechanism does not depend on temperature and that low-temperature magnetotransport data should be treated with caution as they do not necessarily reveal the true ground state, even in the absence of hysteresis.
Let $\chi$ be a primitive Dirichlet character of conductor $q$ and $L(z,\chi)$ the associated L-series. In this paper we provide an explicit upper bound for $|L(1, \chi)|$ when 3 divides $q$.
We study the quantitative pointwise behavior of the solutions of the linearized Boltzmann equation for hard potentials, Maxwellian molecules and soft potentials, with Grad's angular cutoff assumption. More precisely, for solutions inside the finite Mach number region, we obtain the pointwise fluid structure for hard potentials and Maxwellian molecules, and optimal time decay in the fluid part and sub-exponential time decay in the non-fluid part for soft potentials. For solutions outside the finite Mach number region, we obtain sub-exponential decay in the space variable. The singular wave estimate, regularization estimate and refined weighted energy estimate play important roles in this paper. Our results largely extend the classical results of Liu-Yu \cite{[LiuYu], [LiuYu2], [LiuYu1]} and Lee-Liu-Yu \cite% {[LeeLiuYu]} to hard and soft potentials by imposing suitable exponential velocity weight on the initial condition.
We used the data from the Fermi Gamma-ray Space Telescope to characterise the {\gamma}-ray flux variability of blazars on month-like time scales. Our sample consists of 1120 blazars of which 481 are flat spectrum radio quasars (FSRQs) and 639 are BL Lac objects (BL Lacs). We generated monthly binned light curves of our sample for a period of approximately nine years from 2008 August to 2017 December and quantified variability by using excess variance (F_var). On month-like time scales, 371/481 FSRQs are variable ( 80%), while only about 50% (304/639) of BL Lacs are variable. This suggests that FSRQs are more variable than BL Lac objects. We find a mean F_var of 0.55 +/- 0.33 and 0.47 +/- 0.29 for FSRQs and BL Lacs respectively. Large F_var in FSRQs is also confirmed from the analysis of the ensemble structure function. By Dividing our sample of blazars based on the position of the synchrotron peak in their broad-band spectral energy distribution, we find that the low synchrotron peaked (LSP) sources have the largest mean F_var value of 0.54 +/- 0.32 while the intermediate synchrotron peaked (ISP) and high synchrotron peaked (HSP) sources have mean F_var values of 0.45 +/- 0.25 and 0.47 +/- 0.33 respectively. On month-like time scales, we find FSRQs to show a high duty cycle (DC) of variability of 66% relative to BL Lacs that show a DC of 36%. We find that both the F_var and time scale of variability ({\tau}) do not correlate with the black hole mass. We note that F_var is found to be weakly correlated with Doppler factor ({\delta}) and {\tau} is also weakly correlated with {\delta}. Most of the sources in our sample have {\tau} of the order of days, which might be related to processes in the jet. We find marginal difference in the distribution of {\tau} between FSRQs and BL Lacs.
In this paper we use formal group rings to construct an algebraic model of the $T$-equivariant oriented cohomology of smooth toric varieties. Then we compare our model with known results of equivariant cohomology of toric varieties to justify our construction.
Ron Aharoni and Vladimir Korman conjectured that any hypergraph with only finite edges has a strongly minimal cover. We present a counterexample.
We summerize the status of factorization hypothesis in the color-suppressed B meson decays : $B \to J/\psi K^{(*)}$. We present the general formalism for decay rates and polarization fractions with considering all possible non-factorizable contributions which also include the color-octet contributions, and a new factorization scheme comes appear when the universality is exist : $\chi_{F1} = \chi_{A1} = \chi_{A2} = \chi_{V} = \chi$. We consider various phenomenological models to compare their theoretical predictions with the recent CLEO II experimental measurements.
Recently, ``CDM crisis'' is under discussion. The main point of this crisis is that number of substructures presented by cosmological N-body simulations based on CDM scenario for structure formation is much larger than observed substructures. Therefore, it is crucial for this crisis to discriminate whether expected number of CDM substructures really exist but non-luminous or do not exist.   In this paper, we present a new idea to detect such invisible substructures by utilizing a gravitational lensing. Here, we consider quasars that are gravitationally lensed by a foreground galaxy. A substructure around the lensing galaxy may superposed on one of the lensed images of such quasars. In this situation, additional image splitting should occur in the image behind the substructure, and further multiple images are created. This is ``quasar mesolensing''.   We estimate separation and time delay between further multiple images due to quasar mesolensing. The expected value is $1 \sim 30$ milli-arcsecond for the separation and future fine resolution imaging enable us to find invisible substructures, and is $1 \sim 10^3$ second for the time delay and high-speed monitoring of such quasar will be able to find ``echo''-like variation due to quasar mesolensing in intrinsic variability of the quasar. Furthermore, we evaluate that the optical depth for the quasar mesolensing is $\sim 0.1$. Consequently, if we monitor a few multiple quasars, we can find ``echo''-like variation in one of the images after intrinsic flux variations of quasars.
We reconsider the emission properties of the BL Lac objects emitting in the high-energy gamma-ray band exploiting the new information in the MeV-GeV band obtained by the Large Area Telescope (LAT) onboard the Fermi Gamma-Ray Space Telescope in its first three months of operation. To this aim we construct the spectral energy distribution of all the BL Lacs revealed by LAT and of the known TeV BL Lacs not detected by LAT, also including data from the Swift satellite, and model them with a simple one-zone leptonic model. The analysis shows that the BL Lacs detected by LAT (being or not already detected in the TeV band) share similar physical parameters. While some of the TeV BL Lacs not revealed by LAT have spectral energy distributions and physical parameters very similar to the LAT BL Lacs, a group of objects displays peculiar properties (larger electron energies and smaller magnetic fields) suggesting different physical conditions in the emission region. Finally, we discuss possible criteria to effectively select good new candidates for the Cherenkov telescopes among the LAT sources, presenting a list of predicted fluxes in the very high-energy band calculated including the effect of the absorption by the extragalactic background light.
The Berry phase origin is elaborated for the recent-discovered planar spin Hall effect which features current-induced spin polarization within the plane of the Hall deflection. We unravel a spin-repulsion vector governing the planar spin Hall effect, providing a transparent criteria for identifying intrinsic planar spin Hall materials. Finite spin-repulsion vector is found permitted in 13 crystalline point groups, revealing a big number of unexplored planar spin Hall systems. Our result can be used for the quantitative calculation of the planar spin Hall effect, facilitating further material hunting and experimental investigation.
In narrow-band systems, correlated contribution to effective hopping becomes important, and one needs to carefully consider three types of hopping processes: between doubly and singly occupied sites, between singly occupied and empty sites, and between doubly occupied and empty or two singly occupied sites. All three hopping parameters cannot vanish simultaneously, and one should specify for which of these processes the band becomes flat. By means of exact diagonalization of finite systems we demonstrate that three hoppings play qualitatively different roles in many-body effects, in particular, in the formation of half-metallic ferromagnetic (Nagaoka) states.
The production of pairs of hadrons in hadronic collisions is studied using a next-to-leading-order Monte Carlo program based on the phase space slicing technique. Up-to-date fragmentation functions based on fits to LEP data are employed, together with several versions of current parton distribution functions. Good agreement is found with data for the dihadron mass distribution. A comparison is also made with data for the dihadron angular distribution. The scale dependence of the predictions and the dependence on the choices made for the fragmentation and parton distribution functions are also presented. The good agreement between theory and experiment is contrasted to the case for single $\pi^0$ production where significant deviations between theory and experiment have been observed.
Statistical mechanics for states with complex eigenvalues, which are described by Gel'fand triplet and represent unstable states like resonances, are discussed on the basis of principle of equal ${\it a priori}$ probability. A new entropy corresponding to the freedom for the imaginary eigenvalues appears in the theory. In equilibriums it induces a new physical observable which can be identified as a common time scale. It is remarkable that in spaces with more than 2 dimensions we find out existence of stable and quasi-stable systems, even though all constituents are unstable. In such systems all constituents are connected by stationary flows which are generally observable and then we can say that they are semiclassical systems. Examples for such semiclassical systems are constructed in parabolic potential barriers. The flexible structure of the systems is also pointed out.
Mergers of double neutron stars (DNSs) could lead to the formation of a long-lived massive remnant NS, which has been previously suggested to explain the AT 2017gfo kilonova emission in the famous GW170817 event. For an NS-affected kilonova, it is expected that a non-thermal emission component can be contributed by a pulsar wind nebula (PWN), which results from the interaction of the wind from the remnant NS with the preceding merger ejecta. Then, the discovery of such a non-thermal PWN emission can provide an evidence for the existence of the remnant NS. Similar to GRB 170817A, GRB 160821B is also one of the nearest short gamma-ray bursts (SGRBs). A candidate kilonova is widely believed to appear in the ultraviolet-optical-infrared afterglows of GRB 160821B. Here, by modeling the afterglow light curves and spectra of GRB 160821B, we find that the invoking of a non-thermal PWN emission can indeed be well consistent with the observational data. This may indicate that the formation of a stable massive NS could be not rare in the DNS merger events and, thus, the equation of state of the post-merger NSs should be stiff enough.
We show that perfect quantum teleportation can be achieved with mixed photon polarization states when nonlocal memory effects influence the dynamics of the quantum system. The protocol is carried out with a pair of photons, whose initial maximally entangled state is destroyed by local decoherence prior to teleportation. It is demonstrated that the presence of strong nonlocal memory effects, which arise from initial correlations between the environments of the photons, allow to restore perfect teleportation. We further analyze how the amount of initial correlations within the environment affects the fidelity of the protocol, and find that for a moderate amount of correlations the fidelity exceeds the one of the previously known optimal teleportation protocol without memory effects. Our results show that memory effects can be exploited in harnessing noisy quantum systems for quantum communication and that non-Markovianity is a resource for quantum information tasks.
Clinical observations indicate that during critical care at the hospitals, patients sleep positioning and motion affect recovery. Unfortunately, there is no formal medical protocol to record, quantify, and analyze patient motion. There is a small number of clinical studies, which use manual analysis of sleep poses and motion recordings to support medical benefits of patient positioning and motion monitoring. Manual processes are not scalable, are prone to human errors, and strain an already taxed healthcare workforce. This study introduces DECU (Deep Eye-CU): an autonomous mulitmodal multiview system, which addresses these issues by autonomously monitoring healthcare environments and enabling the recording and analysis of patient sleep poses and motion. DECU uses three RGB-D cameras to monitor patient motion in a medical Intensive Care Unit (ICU). The algorithms in DECU estimate pose direction at different temporal resolutions and use keyframes to efficiently represent pose transition dynamics. DECU combines deep features computed from the data with a modified version of Hidden Markov Model to more flexibly model sleep pose duration, analyze pose patterns, and summarize patient motion. Extensive experimental results are presented. The performance of DECU is evaluated in ideal (BC: Bright and Clear/occlusion-free) and natural (DO: Dark and Occluded) scenarios at two motion resolutions in a mock-up and a real ICU. The results indicate that deep features allow DECU to match the classification performance of engineered features in BC scenes and increase the accuracy by up to 8% in DO scenes. In addition, the overall pose history summarization tracing accuracy shows an average detection rate of 85% in BC and of 76% in DO scenes. The proposed keyframe estimation algorithm allows DECU to reach an average 78% transition classification accuracy.