ShantanuT01/DACTYL-Pretraining huggingface dataset:
A quantum system at equilibrium is represented by a corresponding classical system, chosen to reproduce the thermodynamic and structural properties. The objective is to develop a means for exploiting strong coupling classical methods (e.g., MD, integral equations, DFT) to describe quantum systems. The classical system has an effective temperature, local chemical potential, and pair interaction that are defined by requiring equivalence of the grand potential and its functional derivatives with respect to the external and pair potentials for the classical and quantum systems. Practical inversion of this mapping for the classical properties is effected via the hypernetted chain approximation, leading to representations as functionals of the quantum pair correlation function. As an illustration, the parameters of the classical system are determined approximately such that ideal gas and weak coupling RPA limits are preserved.
We study spin transport of holes through stubless or stubbed waveguides modulated periodically by diluted magnetic semiconductor (DMS) sections of width b1 . Injected holes of up (down) spin feel a periodically modulated barrier (well) potential in the DMS sections and have different transmission (T) coefficients. T oscillates with b1 for spin-down and decreases fast for spin-up holes while the relative polarization Pr depends nearly periodically on the stub height. Using asymmetric stubs leads to a nearly square-wave pattern in T and to wide plateaus in Pr . T oscillates with the length between the DMS sections. With two DMS sections per unit, T shows periodically wide gaps for spin-down holes when a DMS width is varied. The results can be used to create efficient spin filters.
In the era of precision cosmology it has became crucial to find new and competitive probes to estimate cosmological parameters, in an effort of finding answers to the current cosmological tensions/discrepancies. In this work, we show the possibility of using observations of Super Massive Black Hole (SMBH) shadows as an anchor for the distance ladder, substituting the sources usually exploited for such purpose, such as Cepheid variable stars. Compared to the standard approaches, the use of SMBH has the advantage of not needing to be anchored with distance calibrators outside the Hubble flow since the shadows physical size can be estimated knowing the mass of the SMBH. Furthermore, SMBH are supposed to inhabit the center of all galaxies which, in principle, means that we can measure the size of the shadows in any Supernova type Ia host galaxy. Under the assumption that the mass of the SMBH can be accurately and reliably estimated, we find that the Hubble constant can be constrained with a $\approx10\%$ precision even considering current experimental design of ground-based interferometers. By constructing a SMBH catalogue based on a specific choice of the SMBH Mass Function (BHMF), we forecast the constraints on the Hubble constant, finding that a precision of $\approx4\%$ may be within reach of future interferometers.
It will be given analytical and numerical evidence supporting that the X-Y model yields an extensive, i.e. proportional to the number of degrees of freedom N, internal energy U for any value of the interaction range.
A superembedding construction of general non-abelian Born-Infeld actions in three dimensions is described. These actions have rigid target space and local worldvolume supersymmetry(i.e. kappa symmetry). The standard abelian Born-Infeld gauge multiplet is augmented with an additional worldvolume SU(N) gauge supermultiplet. It is shown how to construct single-trace actions and in particular a kappa-supersymmetric extension of the symmetrised trace action.
We present an algorithm for explicitly computing the number of generators of the stable cohomology algebra of any rationally smooth partial toroidal compactification of ${\mathcal A}_g$, satisfying certain additivity and finiteness properties, in terms of the combinatorics of the corresponding toric fans. In particular the algorithm determines the stable cohomology of the matroidal partial compactification, in terms of simple regular matroids that are irreducible with respect to the 1-sum operation, and their automorphism groups. The algorithm also applies to compute the stable Betti numbers in close to top degree for the perfect cone toroidal compactification. This suggests the existence of an algebra structure on the stable cohomology of the perfect cone compactification in close to top degree.
We present a general theoretical formalism to compute the fidelity of transformations of unknown quantum states. We then focus on the case of Gaussian transformations of continuous variable quantum systems, where, for the case of a Gaussian distribution of displaced coherent states, the theory is readily tractable by a covariance matrix formalism. We present analytical results for recently implemented teleportation and memory storage protocols for continuous variables.
The real-space imaging of small molecules is always challenging under the electron microscopes, but highly demanded for investigating various nanoscale interactions, such as hydrogen bond and van der Waals (vdW) force. Especially, identifying the host-guest interactions in porous materials directly at the molecular level will bring a deeper insight into the behaviors of guest molecules during the sorption, catalysis, gas separation and energy storage. In this work, we directly resolved the ordered configurations of p-xylenes (PXs) adsorbed in ZSM-5 frameworks by the scanning transmission electron microscopy (STEM) with the integrated differential phase contrast (iDPC) technique to identify the host-guest vdW interactions. Based on these observations, we revealed that the PXs in one straight channel modified the channel geometry with a coherent orientation. And the adjacent straight channels were deformed up to 8.8% along the different directions corresponding to three dominant PX configurations, resulting a negligible overall expansion of ZSM-5 lattices. Then, we could also image the disorder and desorption of PXs in ZSM-5 channels during the in situ heating. This work not only helped us to study the host-guest vdW interactions and the sorption behaviors of PXs in ZSM-5, but also provided an efficient tool for further imaging and studying other single-molecule behaviors under STEMs.
The task of reflection symmetry detection remains challenging due to significant variations and ambiguities of symmetry patterns in the wild. Furthermore, since the local regions are required to match in reflection for detecting a symmetry pattern, it is hard for standard convolutional networks, which are not equivariant to rotation and reflection, to learn the task. To address the issue, we introduce a new convolutional technique, dubbed the polar matching convolution, which leverages a polar feature pooling, a self-similarity encoding, and a systematic kernel design for axes of different angles. The proposed high-dimensional kernel convolution network effectively learns to discover symmetry patterns from real-world images, overcoming the limitations of standard convolution. In addition, we present a new dataset and introduce a self-supervised learning strategy by augmenting the dataset with synthesizing images. Experiments demonstrate that our method outperforms state-of-the-art methods in terms of accuracy and robustness.
In this paper I review a series of observations which do not agree with the standard interpretation of the extinction curve. The consequence is that light we receive from a reddened star must be contaminated by starlight scattered at very small angular distances from the star. The true extinction curve is a straight line from the near infrared to the far-UV. If so, all interstellar grains models must be questionned. Another conclusion concerns the average properties of interstellar grains which seem much more uniform than previously thought.
In this paper, assuming the validity of distance duality relation, $\eta=D_L(z)(1+z)^{-2}/D_A(z)=1$, where $D_A(z)$ and $D_L(z)$ are the angular and the luminosity distance respectively, we explore two kinds of gas mass density profiles of clusters: the isothermal $\beta$ model and the non-isothermal double-$\beta$ model. In our analysis, performed on 38 massive galaxy clusters observed by \textit{Chandra} (within the redshift range of $0.14<z<0.89$), we use two types of cluster gas mass fraction data corresponding to different mass density profiles fitted to the X-ray data. Using two general parameterizations of $\eta(z)$ (phenomenologically allowing for distance duality violation), we find that the non-isothermal double-$\beta$ model agrees better with the distance duality relation, while the isothermal $\beta$ model tends to be marginally incompatible with the Etherington theorem at 68.3% CL. However, current accuracy of the data does not allow to distinguish between the two models for the gas-density distribution at a significant level.
A model to calculate nuclear responses considering short-range correlation effects is presented. The model is applied to the study of electromagnetic responses induced by one-body operators. We calculate one- and two-nucleon emission responses and cross sections of the 16O and 40Ca nuclei in the quasi-elastic region, and we compare them with experimental data.
Recently Wagner et al. [Phys. Rev. Lett. Vol. 81, P. 3980 (1998)] proposed that Mott's original model be modified to incorporate a hopping barrier which depends on the misorientation between the spins of electrons at the initial and the final states in an elementary process. They further claimed that using the model they can explain the observed scaling behavior-- negative-magnetoresistivity scaling proportional to the Brillouin function $\cal{B}$ in the ferromagnetic state and to ${\cal{B}}^2$ in the paramagnetic state. In this comment we argue that the modification needed for Mott's original model is different from that proposed by Wagner et al. and further show that our picture will successfully explain the observed scaling in the two regimes.
In the frame of Mahler's method for algebraic independence we show that the algebraic relations over Q linking the values of functions solutions of a system of functional equations come from the algebraic relations between the functions themselves, by specialisation. We deduce some results on the linear independence of the q-regular functions.
Surface tension in drops has been investigated mainly from a thermodynamic standpoint, more rarely with kinetic methods. In the present work, this problem is studied in the framework of kinetic theory, starting from Sutherland's approximation for Van Der Waals interaction between molecules. Surface tension is calculated as a function of drop radius: it is found that it approaches swiftly an asymptotic value, for radii of several times the intermolecular distance. This theoretical asymptotic value is compared to experimental values for a few liquids, and is found in reasonable agreement.
The loop expansion is applied to a chiral effective hadronic lagrangian; with the techniques of Infrared Regularization, it is possible to separate out the short-range contributions and to write them as local products of fields that are already present in our lagrangian. (The appropriate field variables must be re-defined at each order in loops.) The corresponding parameters implicitly include short-range effects to all orders in the interaction, so these effects need not be calculated explicitly. The remaining (long-range) contributions that must be calculated are nonlocal and resemble those in conventional nuclear-structure calculations. Nonlinear isoscalar scalar $(\sigma)$ and vector $(\omega)$ meson interactions are included, which incorporate many-nucleon forces and nucleon substructure. Calculations are carried out at the two-loop level to illustrate these techniques at finite nuclear densities and to verify that the coupling parameters remain natural when fitted to the empirical properties of equilibrium nuclear matter. Contributions from the $\omega N$ tensor coupling are also discussed.
The spreading of SARS will destruct the initial network structure to a new phase, and in turn the spreading process will be weakened effectively and finally halted by this evolution of network structure. This mechanism is called immunity of contact network in this paper. What we can do is to accelerate effectively this process only.
We present the results of a comprehensive magneto-optical characterization of single CdTe quantum dots containing a few Mn2+ ions. We find that some quantum dots exhibit an unexpected evolution of excitonic photoluminescence spectrum with the magnetic field. At a certain value of the magnetic field, specific for every quantum dot, each of the broad spectral lines related to the recombination of various excitonic complexes confined inside the dot transforms into a pair of narrow lines split by several meV. We interpret this abrupt change in the character of excitonic emission spectrum as a consequence of a transition from a non-polarized state of the Mn2+ spins in a low field regime to a highly (almost fully) polarized state above the critical magnetic field. Various optical experiments, including polarization-resolved studies, investigation of different excitation regimes and time-resolved measurements corroborate this scenario. However, these measurements indicate also that the observed effect is not related or influenced by the photo-created charge carriers, but it is rather originating from unusual spin configuration in the cluster of Mn2+ ions.
Supernova remnants (SNRs) have long been assumed to be the source of cosmic rays (CRs) up to the "knee" of the CR spectrum at 10^15 eV, accelerating particles to relativistic energies in their blast waves by the process of diffusive shock acceleration (DSA). Since cosmic ray nuclei do not radiate efficiently, their presence must be inferred indirectly. Previous theoretical calculations and X-ray observations show that CR acceleration modifies significantly the structure of the SNR and greatly amplifies the interstellar magnetic field. We present new, deep X-ray observations of the remnant of Tycho's supernova (SN 1572, henceforth Tycho), which reveal a previously unknown, strikingly ordered pattern of non-thermal high-emissivity stripes in the projected interior of the remnant, with spacing that corresponds to the gyroradii of 10^14 - 10^15 eV} protons. Spectroscopy of the stripes shows the plasma to be highly turbulent on the (smaller) scale of the Larmor radii of TeV energy electrons. Models of the shock amplification of magnetic fields produce structure on the scale of the gyroradius of the highest energy CRs present, but they do not predict the highly-ordered pattern we observe. We interpret the stripes as evidence for acceleration of particles to near the knee of the CR spectrum in regions of enhanced magnetic turbulence, while the observed highly ordered pattern of these features provides a new challenge to models of DSA.
Globular clusters are large collections of old stars that are orbiting the core of a galaxy. Our Milky Way Galaxy has about 160 known clusters, with perhaps more to be discovered. We first accumulated the necessary parameters for 16 clusters and ran a numerical model that predicts the inverse Compton gamma-ray flux expected from each cluster. We also reanalysed data from 16 clusters observed by the H.E.S.S. very-high-energy (> 100 GeV) gamma-ray telescopes. We confirmed the detection of Terzan 5 and found flux upper limits for the remaining 15 sources that were consistent with published results. We attempted to constrain some source parameters using X-ray and gamma-ray data. We lastly list the five most promising clusters for future observations by the Cherenkov Telescope Array.
We present an exact solution of the Langevin's equation in the steady state limit in a three dimensional, harmonic crystal of slab geometry whose boundary surfaces along its length are connected to two stochastic, white noise heat baths at different temperatures. We show that the heat trasport obeys the Fourier's law in the continuum limit.
In this paper, we investigate a class of Horndeski scalar-tensor theory of gravity for warm inflation. We present some models where the early-time acceleration is realized in the weak and in the strong dissipation regime. Cosmological perturbations are analyzed.
We consider the Kardar-Parisi-Zhang (KPZ) equation for a circular interface in two dimensions, unconstrained by the standard small-slopes and no-overhang approximations. Numerical simulations using an adaptive scheme allow us to elucidate the complete time evolution as a crossover between a short-time regime with the interface fluctuations of a self-avoiding ring or 2D vesicle, and a long-time regime governed by the Tracy-Widom distribution expected for this geometry. For small noise amplitudes, scaling behavior is only of the latter type. Large noise is also seen to renormalize the bare physical parameters of the ring, akin to analogous parameter renormalization for equilibrium 3D membranes. Our results bear particular importance on the relation between relevant universality classes of scale-invariant systems in two dimensions.
Decoupling limits of physical interest occur in regions of space--time where the string coupling diverges. This is illustrated in the celebrated example of five-branes. There are several ways to overcome this strong-coupling problem. We review those which are somehow related to two-dimensional conformal field theories. One method consists of distributing the branes over transverse space, either on a circle or over a sphere. Those distributions are connected to conformal field theories by T-dualities or lead to a new kind of sigma model where the target space is a patchwork of pieces of exact conformal-field-theory target spaces. An alternative method we discuss is the introduction of diluted F-strings, which trigger a marginal deformation of an AdS$_3\times S^3\times T^4$ background with a finite string coupling. Our discussion raises the question of finding brane configurations, their spectrum, their geometry, and their interpretation in terms of two-dimensional conformal models.
We report on the Herschel Gould Belt survey (HGBS) of ChaII, focusing on the detection of Class I to III young stellar objects (YSOs). We aim at characterizing the circumstellar material around these YSOs and understanding which disk parameters are most likely constrained by the new HGBS data. We recovered 29 out of the 63 known YSOs in ChaII with a detection in at least one of the PACS/SPIRE pass-bands: 3 Class I YSOs (i.e.,100%), 1 Flat source (i.e., 50%), 21 Class II objects (i.e., 55%), 3 Class III objects (i.e, 16%) and the unclassified source IRAS 12522-7640. We explore PACS/SPIRE colors of this sample and present modeling of their SEDs using the RADMC-2D radiative transfer code. We find that YSO colors are confined in specific regions of PACS/SPIRE color-color diagrams. These color ranges are expected to be only marginally contaminated by extragalactic sources and field stars and, hence, provide a useful YSO selection tool when applied altogether. We were able to model the SED of 26 out of the 29 detected YSOs. We discuss the degeneracy/limitations of our SED fitting results and adopt the Bayesian method to estimate the probability of different values for the derived disk parameters. The Cha II YSOs present typical disk inner radii around 0.1 AU. The lower limit to Rc is typically around 50 AU. The lower limits to Mdisk are proportional to the stellar masses with a typical 0.3% ratio, i.e., in the range estimated in the literature for young Class II stars and brown dwarfs across a broad range of stellar masses. The estimated flaring angles, although very uncertain, point towards rather flat disks (1+phi less than 1.2), as found for low-mass M-type YSO samples in other star forming regions. Thus, our results support the idea that disk properties show a dependence on stellar properties.
The fine structure of the scissors mode is investigated within the Time Dependent Hartree-Fock-Bogoliubov (TDHFB) approach. The solution of TDHFB equations by the Wigner Function Moments (WFM) method predicts a splitting of the scissors mode into three intermingled branches. Together with the conventional scissors mode two new modes arise due to spin degrees of freedom. They generate significant $M1$ strength below the conventional energy range. The results of calculations of scissors resonances in Rare Earths and Actinides by WFM and QPNM methods are compared with experimental data. A remarkable coherence of both methods together with experimental data is observed.
We consider charge transport through a nanoscopic object, e.g. single molecules, short nanotubes, or quantum dots, that is weakly coupled to metallic electrodes. We account for several levels of the molecule/quantum dot with level-dependent coupling strengths, and allow for relaxation of the excited states. The current-voltage characteristics as well as the current noise are calculated within first-order perturbation expansion in the coupling strengths. For the case of asymmetric coupling to the leads we predict negative-differential-conductance accompanied with super-poissonian noise. Both effects are destroyed by fast relaxation processes. The non-monotonic behavior of the shot noise as a function of bias and relaxation rate reflects the details of the electronic structure and level-dependent coupling strengths.
Let $L(s,\chi)$ be the Dirichlet $L$-function associated to a non trivial primitive Dirichlet character $\chi$ defined $\bmod\ q$, where $q$ is an odd prime. In this paper we introduce a fast method to compute $\vert L(1,\chi) \vert$ using the values of Euler's $\Gamma$ function. We also introduce an alternative way of computing $\log \Gamma(x)$ and $\psi(x)= \Gamma^\prime/\Gamma(x)$,$x\in(0,1)$. Using such algorithms we numerically verify the classical Littlewood bounds and the recent Lamzouri-Li-Soundararajan estimates on $\vert L(1,\chi) \vert$, where $\chi$ runs over the non trivial primitive Dirichlet characters $\bmod\ q$, for every odd prime $q$ up to $10^7$. The programs used and the results here described are collected at the following address \url{http://www.math.unipd.it/~languasc/Littlewood_ineq.html}.
We propose a simple and efficient real-space approach for the calculation of the ground-state energies of Wigner crystals in 1, 2, and 3 dimensions. To be precise, we calculate the first two terms in the asymptotic expansion of the total energy per electron which correspond to the classical energy and the harmonic correction due to the zero-point motion of the Wigner crystals, respectively. Our approach employs Clifford periodic boundary conditions to simulate the infinite electron gas and a renormalized distance to evaluate the Coulomb potential. This allows us to calculate the energies unambiguously and with a higher precision than those reported in the literature. Our results are in agreement with the literature values with the exception of harmonic correction of the 2-dimensional Wigner crystal for which we find a significant difference. Although we focus on the ground state, i.e., the triangular lattice and the body-centered cubic lattice, in two and three dimensions, respectively, we also report the classical energies of several other common lattice structures.