ShantanuT01/DACTYL-Pretraining huggingface dataset:
Charm and bottom transport coefficients in a medium constituted of light mesons, such as is formed in the hadronic phase of Heavy Ion Collisions, are obtained within an effective field theory approach implementing heavy quark symmetry and chiral symmetry breaking. Heavy flavor propagates in the medium as $D/B$ and $D^*/B^*$ degrees of freedom, and unitarization of the lowest order heavy-light meson amplitudes is used in order to reach high temperatures. The latter accounts for dynamically generated resonances in isospin 1/2 channels, a feature that leads to a more efficient heavy flavor diffussion. We discuss the temperature and momentum dependence of the friction and diffusion coefficients in a transport approach up to temperatures of about $T\simeq 150$ MeV, and provide estimates of the charm/bottom relaxation lengths and momentum loss. Implications for heavy meson spectrum observables in Heavy Ion Collisions are discussed.
Improvements in the thermoelectric properties of Half-Heusler materials have been achieved by means of a micrometer-scale phase separation that increases the phonon scattering and reduces the lattice thermal conductivity. A detailed study of the p-type Half-Heusler compounds Ti(1-x)Hf(x)CoSb0.85Sn0.15 using high-resolution synchrotron powder X-ray diffraction and element mapping electron microscopy evidences the outstanding thermoelectric properties of this system. A combination of intrinsic phase separation and adjustment of the carrier concentration via Sn substitution is used to realize a record thermoelectric figure of merit for p-type Half-Heusler compounds of ZT around 1.15 at 710C in Ti0.25Hf0.75CoSb0.85Sn0.15. The phase separation approach can form a significant alternative to nanostructuring processing time, energy consumption and increasing the thermoelectric efficiency.
SrRuO3 is an itinerant ferromagnet with orthorhombic structure and uniaxial magnetocrystalline anisotropy - features expected to yield resistivity anisotropy. Here we explore changes in the resistivity anisotropy of epitaxial SrRuO3 films due to induced magnetization in the paramagnetic state by using the planar Hall effect. We find that the effect of the induced magnetization on the in-plane anisotropy is strongly angular dependent, and we provide a full description of this behavior at 160 K for induced magnetization in the (001) plane.
For the focusing mass-critical NLS $iu_t+\Delta u=-|u|^{\frac 4d}u$, it is conjectured that the only global non-scattering solution with ground state mass must be a solitary wave up to symmetries of the equation. In this paper, we settle the conjecture for $H^1_x$ initial data in dimensions $d=2,3$ with spherical symmetry and $d\ge 4$ with certain splitting-spherically symmetric initial data.
We consider a quantum cosmology with a massless background scalar field $\pb$ and adopt a wave packet as the wave function. This wave packet is a superposition of the WKB form wave functions, each of which has a definite momentum of the scalar field $\pb$. In this model it is shown that to trace the formalism of the WKB time is seriously difficult without introducing a complex value for a time. We define a semiclassical real time variable $\tp$ from the phase of the wave packet and calculate it explicitly. We find that, when a quantum matter field $\pq$ is coupled to the system, an approximate Schr\"odinger equation for $\pq$ holds with respect to $\tp$ in a region where the size $a$ of the universe is large and $|\pb|$ is small.
Motivated by a model of an area-wide integrated pest management, we develop an interacting particle system evolving in a random environment. It is a generalised contact process in which the birth rate takes two possible values, determined either by a dynamic or a static random environment. Our goal is to understand the phase diagram of both models by identifying the mechanisms that permit coexistence or extinction of the process.
We study level-set percolation of the Gaussian free field on the infinite $d$-regular tree for fixed $d\geq 3$. Denoting by $h_\star$ the critical value, we obtain the following results: for $h>h_\star$ we derive estimates on conditional exponential moments of the size of a fixed connected component of the level set above level $h$; for $h<h_\star$ we prove that the number of vertices connected over distance $k$ above level $h$ to a fixed vertex grows exponentially in $k$ with positive probability. Furthermore, we show that the percolation probability is a continuous function of the level $h$, at least away from the critical value $h_\star$. Along the way we also obtain matching upper and lower bounds on the eigenfunctions involved in the spectral characterisation of the critical value $h_\star$ and link the probability of a non-vanishing limit of the martingale used therein to the percolation probability. A number of the results derived here are applied in the accompanying paper [AC2].
In this paper we deal with the compressible Navier-Stokes equations with a friction term in one dimension on an interval. We study the exact controllability properties of this equation with general initial condition when the boundary control is acting at both endpoints of the interval. Inspired by the work of Guerrero and Imanuvilov in \cite{GI} on the viscous Burger equation, we prove by choosing irrotational data and using the notion of effective velocity developed in \cite{cpde,cras} that the exact global controllability result does not hold for any time $T$.
Normal parity bands are studied in 157Gd, 163Dy and 169Tm using the pseudo SU(3) shell model. Energies and B(E2) transition strengths of states belonging to six low-lying rotational bands with the same parity in each nuclei are presented. The pseudo SU(3) basis includes states with pseudo-spin 0 and 1, and 1/2 and 3/2, for even and odd number of nucleons, respectively. States with pseudo-spin 1 and 3/2 must be included for a proper description of some excited bands.
We present a comparison of the statistical properties of dark matter halo merger trees extracted from the Millennium Simulation with Extended Press-Schechter (EPS) formalism and the related GALFORM Monte-Carlo method for generating ensembles of merger trees. The volume, mass resolution and output frequency make the Millennium Simulation a unique resource for the study of the hierarchical growth of structure. We construct the merger trees of present day friends-of-friends groups and calculate a variety of statistics that quantify the masses of their progenitors as a function of redshift; accretion rates; and the redshift distribution of their most recent major merger. We also look in the forward direction and quantify the present day mass distribution of halos into which high redshift progenitors of a specific mass become incorporated. We find that EPS formalism and its Monte-Carlo extension capture the qualitative behaviour of all these statistics but, as redshift increases they systematically underestimate the masses of the most massive progenitors. This shortcoming is worst for the Monte-Carlo algorithm. We present a fitting function to a scaled version of the progenitor mass distribution and show how it can be used to make more accurate predictions of both progenitor and final halo mass distributions.
We are concerned with the dynamics of one fold symmetric patches for the two-dimensional aggregation equation associated to the Newtonian potential. We reformulate a suitable graph model and prove a local well-posedness result in sub-critical and critical spaces. The global existence is obtained only for small initial data using a weak damping property hidden in the velocity terms. This allows to analyze the concentration phenomenon of the aggregation patches near the blow up time. In particular, we prove that the patch collapses to a collection of disjoint segments and we provide a description of the singular measure through a careful study of the asymptotic behavior of the graph.
We have made a detailed temperature-dependent photoemission study of VO_2/TiO_2(001) thin films, which show a metal-insulator transition at \sim 300 K. Clean surfaces were obtained by annealing the films in an oxygen atmosphere. Spectral weight transfer between the coherent and incoherent parts accompanying the metal-insulator transition was clearly observed. We also observed a hysteretic behavior of the spectra for heating-cooling cycles. We have derived the ``bulk'' spectrum of the metallic phase and found that it has a strong incoherent part. The width of the coherent part is comparable to that given by band-structure calculation in spite of its reduced spectral weight, indicating that the momentum dependence of the self-energy is significant. This is attributed to by ferromagnetic fluctuation arising from Hund's rule coupling between different d orbitals as originally proposed by Zylbersztejn and Mott. In the insulating phase, the width of the V 3d band shows strong temperature dependence. We attribute this to electron-phonon interaction and have reproduced it using the independent boson model with a very large coupling constant.
By using the stellar evolution code MESA we show that most of the hydrogen recombination energy that is released as the envelope expands during a regular common envelope evolution (CEE), namely, the initial dynamical phase or plunge-in phase, is radiated, and hence increases substantially the stellar luminosity. Only about ten per cent of the hydrogen recombination energy might be used to remove the envelope. We show that the key property of energy transport is that when convection becomes inefficient in the outer parts of the envelope, where the ionization degree of hydrogen falls below about 30 per cent, photon diffusion becomes very efficient and removes the recombination energy. The expanding envelope absorbs most of the gravitational energy that is released by the spiraling-in process of the secondary star inside the common envelope, and so it is the hydrogen recombination energy that is behind most of the luminosity increase of the system. The recombination energy of hydrogen adds only a small fraction of the energy required to remove the common envelope, and hence does not play a significant role in the ejection of the envelope.
We provide quantitative gradient bounds for solutions to certain parabolic equations with unbalanced polynomial growth and non-smooth coefficients.
The realization of long range and insulating ferromagnetic states in topological insulator (TI) has been a pressing issue since its discovery. Only recently, such state was achieved in Cr-doped Bi2-xSbxTe3, leading to the discovery of quantum anomalous Hall effect (QAHE). However, the effect is only observed at extremely low temperatures mainly due to the limited magnetism. To fully understand the mechanism of the ferromagnetic ordering whereby improving the ferromagnetism, we investigated 4f transition metal-doped Bi2Se3, using density-functional-theory approaches. We found that Eu and Sm prefer the Bi substitutional sites with large magnetic moments to ensure stable long-range ferromagnetic states. Additionally, codoping can be a novel strategy to preserve the insulating property of the host material as well as improving the incorporation of magnetic dopants. Our findings thus offer the critical step in facilitating the realization of QAHE in TI systems.
We propose deterministic realizations of nonlinear phase gates by repeating non-commuting Rabi interactions feasible between a harmonic oscillator and {\em only} a single two-level ancillary qubit. We show explicitly that the key nonclassical features of the states after the ideal cubic phase gate and the quartic phase gate are reproduced faithfully by the engineered operators. This theoretical proposal completes the universal set of operators in continuous variable quantum computation.
We report low temperature high magnetic field scanning tunneling microscopy and spectroscopy of graphene flakes on graphite that exhibit the structural and electronic properties of graphene decoupled from the substrate. Pronounced peaks in the tunneling spectra develop with field revealing a Landau level sequence that provides a direct way to identify graphene and to determine the degree of its coupling to the substrate. The Fermi velocity and quasiparticle lifetime, obtained from the positions and width of the peaks, provide access to the electron-phonon and electron-electron interactions.
The incompressible Euler equations on a compact Riemannian manifold $(M,g)$ take the form \begin{align*} \partial_t u + \nabla_u u &= - \mathrm{grad}_g p \\ \mathrm{div}_g u &= 0, \end{align*} where $u: [0,T] \to \Gamma(T M)$ is the velocity field and $p: [0,T] \to C^\infty(M)$ is the pressure field. In this paper we show that if one is permitted to extend the base manifold $M$ by taking an arbitrary warped product with a torus, then the space of solutions to this equation becomes "non-rigid'"in the sense that a non-empty open set of smooth incompressible flows $u: [0,T] \to \Gamma(T M)$ can be approximated in the smooth topology by (the horizontal component of) a solution to these equations. We view this as further evidence towards the "universal" nature of Euler flows.
We consider conditions for jet break-out through ejecta following mergers of neutron stars and provide simple relations for the break out conditions. We demonstrate that: (i) break-out requires that the isotropic-equivalent jet energy $E_j$ exceeds the ejecta energy $E_{ej}$ by $E_j \geq E_{ej}/ \beta_0$, where $ \beta_0 = V_{ej}/c$, $V_{ej}$ is the maximum velocity of the ejecta. If the central engine terminates before the break out, the shock approaches the edge of the ejecta slowly $\propto 1/t$; late break out occurs only if at the termination moment the head of the jet was relatively close to the edge. (ii) If there is a substantial delay between the ejecta's and the jet's launching, the requirement on the jet power increases. (iii) The forward shock driven by the jet is mildly strong, with Mach number $M\approx 5/4$ (increasing with time delay $t_d$); (iii) the delay time $t_d$ between the ejecta and the jet's launching is important for $t_d > t_0= ({3 }/{16} ) {c M_{ej} V_{ej}}/{L_j} = 1.01 {\rm sec} M_{ej, -2} L_{j, 51} ^{-1} \left ( {\beta_{ej}} /{0.3} \right)$, where $M_{ej}$ is ejecta mass, $L_j$ is the jet luminosity (isotropic equivalent). For small delays, $t_0 $ is also an estimate of the break-out time.
Perovskite/Si tandem solar cells have the potential to considerably out-perform conventional solar cells. Under standard test conditions, perovskite/Si tandem solar cells already outperform the Si single junction. Under realistic conditions, however, as we show, those tandem solar cells are hardly more efficient than the Si cell alone. We model the performance of realistic perovskite/Si tandem solar cells under real-world climate conditions, by incorporating parasitic cell resistances, non-radiative recombination, and optical losses into the detailed-balance limit. We show quantitatively that optimizing these parameters in the perovskite top cell, perovskite/Si tandem solar cells reach an efficiency advantage of up to 14% absolute, even while leaving the Si cell untouched. Despite the rapid efficiency increase of perovskite solar cells, our results emphasize the need for further material development, careful device design, and light management strategies, all necessary for highly efficient perovskite/Si tandem solar cells.
We report the discovery of an IR-selected massive galaxy cluster in the IRAC Distant Cluster Survey (IDCS). We present new data from the Hubble Space Telescope and the W. M. Keck Observatory that spectroscopically confirm IDCS J1426+3508 at z=1.75. Moreover, the cluster is detected in archival Chandra data as an extended X-ray source, comprising 54 counts after the removal of point sources. We calculate an X-ray luminosity of L{0.5-2 keV} = (5.5 +/- 1.2) X 1e44 ergs/s within r = 60 arcsec (~1 Mpc diameter), which implies M_{200,L_x} = (5.6 +/- 1.6) X 1e14 Msun. IDCS J1426+3508 appears to be an exceptionally massive cluster for its redshift.
The time-resolved photoluminescence (PL) characteristics of single CdSe/ZnS nanoparticles, embedded in a PMMA layer is studied at room temperature. We observe a strong spectral jitter of up to 55 meV, which is correlated with a change in the observed linewidth. We evaluate this correlation effect using a simple model, based on the quantum confined Stark effect induced by a diffusing charge in the vicinity of the nanoparticle. This allows us to derive a mean distance between the center of the particle and the diffusing charge of approximately 3.3 nm on average, as well as a mean charge carrier displacement within the integration time. The distances are larger than the combined radius of particle core and shell of about 3 nm, but smaller than the overall radius of 5 nm including ligands. These results are reproducible, even for particles which exhibit strong blueing, with shifts of up to 150 meV. Both the statistics and its independence of core-shell alterations lead us to conclude that the charge causing the spectral jitter is situated in the ligands.
The Gemini/HST Galaxy Cluster Project (GCP) covers 14 z=0.2-1.0 clusters with X-ray luminosity of L_500 >= 10^44 ergs/s in the 0.1-2.4 keV band. In this paper we provide homogeneously calibrated X-ray luminosities, masses and radii, and we present the complete catalog of the ground-based photometry for the GCP clusters. The clusters were observed with Gemini North or South in three or four of the optical passbands g', r', i' and z'. The photometric catalog includes consistently calibrated total magnitudes, colors, and geometrical parameters. The photometry reaches ~25 mag in the passband closest to rest frame B-band. We summarize comparisons of our photometry with data from the Sloan Digital Sky Survey. We describe the sample selection for our spectroscopic observations, and establish the calibrations to obtain rest frame magnitudes and colors. Finally, we derive the color-magnitude relations for the clusters and briefly discuss these in the context of evolution with redshift. Consistent with our results based on spectroscopic data, the color-magnitude relations support passive evolution of the red-sequence galaxies. The absence of change in the slope with redshift, constrains the allowable age variation along the red sequence to <0.05 dex between the brightest cluster galaxies and those four magnitudes fainter. The paper serves as the main reference for the GCP cluster and galaxy selection, X-ray data and ground-based photometry.
We present an observational study of the impacts of the interactions on the stellar population in a sample of galaxy pairs. Long-slit spectra in the wavelength range 3440-7300 {\AA} obtained with the Gemini Multi-Object Spectrograph (GMOS) at Gemini South for fifteen galaxies in nine close pairs were used. The spatial distributions of the stellar population contributions were obtained using the stellar population synthesis code STARLIGHT. Taking into account the different contributions to the emitted light, we found that most of the galaxies in our sample are dominated by the young/intermediate stellar populations. This result differs from the one derived for isolated galaxies where the old stellar population dominates the disc surface brightness. We interpreted such different behavior as being due to the effect of gas inflows along the disk of interacting galaxies on the star formation in a time scale of the order of about 2Gyr. We also found that, in general, the secondary galaxy of the pairs has a higher contribution of the young stellar population than the primary one. We compared the estimated values of the stellar and nebular extinctions derived from the synthesis method and the H{\alpha}/H\b{eta} emission-line ratio finding that the nebular extinctions are systematically higher than stellar ones by about a factor of 2. We did not find any correlation between nebular and stellar metallicities. We neither found a correlation between stellar metallicities and ages while a positive correlation between nebular metallicities and stellar ages was obtained, with the older regions being the most metal-rich.
We investigate the role of boundary conditions in gauge theories in AdS4. The presence of the boundary can break the gauge symmetry consistently with AdS4 isometries. We show that, as a consequence, the gauge bosons associated to the broken symmetries become massive at one loop. In particular chiral gauge theories such us the Standard Model are necessarily massive in AdS4. We briefly discuss similarities with the Schwinger model and implications for CFTs in three dimensions.
We report on high-resolution spectropolarimetric observations of the hot subdwarf stars HD 76431 and Feige 66, using the ESPaDOnS echelle spectropolarimeter at CFHT. We compute cross-correlation Stokes I and V line profiles to enhance the signal-to-noise ratio. We then average all available cross-correlation profiles of each star to further decrease the noise level. Although both targets were previously reported to host kilo-gauss magnetic fields, we do not derive any evidence of large-scale photospheric fields from our sets of observations, in spite of tight error bars on the longitudinal field of the order of 60 gauss for HD 76431 and 200 gauss for Feige 66. A new analysis of FORS1 observations of HD 76431, which provided the basis for the original claim of field detection, confirms the absence of any detectable Zeeman signature, with an error bar of about 100 gauss on the longitudinal magnetic field.
Astrometric observations of S-stars provide a unique opportunity to probe the nature of Sagittarius-A* (Sgr-A*). In view of this, it has become important to understand the nature and behavior of timelike bound trajectories of particles around a massive central object. It is known now that whereas the Schwarzschild black hole does not allow the negative precession for the S-stars, the naked singularity spacetimes can admit the positive as well as negative precession for the bound timelike orbits. In this context, we study the perihelion precession of a test particle in the Kerr spacetime geometry. Considering some approximations, we investigate whether the timelike bound orbits of a test particle in Kerr spacetime can have negative precession. In this paper, we only consider low eccentric timelike equatorial orbits. With these considerations, we find that in Kerr spacetimes, negative precession of timelike bound orbits is not allowed.
We demonstrate how to parallelize the density matrix renormalization group (DMRG) algorithm in real space through a straightforward modification of serial DMRG. This makes it possible to apply at least an order of magnitude more computational power to challenging simulations, greatly accelerating investigations of two-dimensional systems and large parameter spaces. We discuss details of the algorithm and present benchmark results including a study of valence-bond-solid order within the square-lattice Q2 model and Neel order within the triangular lattice Heisenberg model. The parallel DMRG algorithm also motivates an alternative canonical form for matrix product states.
In this work we perform an analysis on the recently proposed conjoined cosmic growth and cosmic expansion diagram [1] to compare several dark energy models using the Figure of Merit showed in [2], which consists in the inverse of the $1\sigma$ confidence region in the $f\sigma_8(z)-H(z)$ plot. Our analysis also consists of comparing the models by performing different statistical criteria: Bayes factor [3], the Bayesian Information Criteria [4] and the Akaike Information Criterion [5]. We also developed a 3-dimensional Figure of Merit to account simultaneously for the errors on the growth rate and the Hubble parameter. The main idea is to consider several cosmological models and compare them with the different statistical criteria in order to highlight the differences and the accuracies of each single criterion.