ShantanuT01/DACTYL-Pretraining huggingface dataset:
We have proposed several 1D and 2D electronic models with the exact ground state. The ground state wave function of these models is represented in terms of "singlet bond" functions consisting of homopolar and ionic configurations. The Hamiltonians of the models include the correlated hopping of electrons, pair hopping terms and the spin interactions. One of the 1D models demonstrates spontaneous breaking of the translational symmetry. We studied also the model describing the transition point between the phases with and without an off-diagonal long-range order.
The commensurate $p/q$-filled $n$-component Hubbard chain was investigated by bosonization and high-precision density-matrix renormalization-group analysis. It was found that depending on the relation between the number of components $n$, and the filling parameter $q$, the system shows metallic or insulating behavior, and for special fillings bond-ordered (dimerized, trimerized, tetramerized etc.) ground state develops in the insulating phase. A mean-field analysis shows that this bond ordering is a direct consequence of the spin-exchange interaction, which plays a crucial role in the one-parameter Hubbard model -- not only for infinite Coulomb repulsion, but for intermediate values as well.
We find the conditions under which a quantum regression theorem can be assumed valid for non-Markovian master equations consisting in Lindblad superoperators with memory kernels. Our considerations are based on a generalized Born-Markov approximation, which allows us to obtain our results from an underlying Hamiltonian description. We demonstrate that a non-Markovian quantum regression theorem can only be granted in a stationary regime if the dynamics satisfies a quantum detailed balance condition. As an example we study the correlations of a two level system embedded in a complex structured reservoir and driven by an external coherent field.
We consider a graphene sheet in the vicinity of a substrate, which contains charged impurities. An analytic expression for the probability distribution function of voltage fluctuations due to the charged impurities is derived. The distribution function is shown to be non-Gaussian. The voltage fluctuations lead to the appearance of randomly distributed density inhomogeneities in the graphene plane. We argue that these disorder-induced density fluctuations produce a finite conductivity even at a zero gate voltage in accordance with recent experimental observations. We estimate the width of the minimal conductivity plateau and the typical size of the electron and hole puddles. The existence of inhomogeneous random puddles of electrons and holes should be a generic feature of all graphene layers at low gate voltages due to the invariable presence of charged impurities in the substrate.
We performed a 4.5-month multi-instrument campaign (from radio to VHE gamma rays) on Mrk421 between January 2009 and June 2009, which included VLBA, F-GAMMA, GASP-WEBT, Swift, RXTE, Fermi-LAT, MAGIC, and Whipple, among other instruments and collaborations. Mrk421 was found in its typical (non-flaring) activity state, with a VHE flux of about half that of the Crab Nebula, yet the light curves show significant variability at all wavelengths, the highest variability being in the X-rays. We determined the power spectral densities (PSD) at most wavelengths and found that all PSDs can be described by power-laws without a break, and with indices consistent with pink/red-noise behavior. We observed a harder-when-brighter behavior in the X-ray spectra and measured a positive correlation between VHE and X-ray fluxes with zero time lag. Such characteristics have been reported many times during flaring activity, but here they are reported for the first time in the non-flaring state. We also observed an overall anti-correlation between optical/UV and X-rays extending over the duration of the campaign.   The harder-when-brighter behavior in the X-ray spectra and the measured positive X-ray/VHE correlation during the 2009 multi-wavelength campaign suggests that the physical processes dominating the emission during non-flaring states have similarities with those occurring during flaring activity. In particular, this observation supports leptonic scenarios as being responsible for the emission of Mrk421 during non-flaring activity. Such a temporally extended X-ray/VHE correlation is not driven by any single flaring event, and hence is difficult to explain within the standard hadronic scenarios. The highest variability is observed in the X-ray band, which, within the one-zone synchrotron self-Compton scenario, indicates that the electron energy distribution is most variable at the highest energies.
We use AdS_5 x S^5 superstring sigma model perturbation theory to compute the leading one-loop corrections to the dispersion relations of the excitations near a long spinning string in AdS. This investigation is partially motivated by the OPE-based approach to the computation of the expectation value of null polygonal Wilson loops suggested in arXiv:1006.2788. Our results are in partial agreement with the recent asymptotic Bethe ansatz computation in arXiv:1010.5237. In particular, we find that the heaviest AdS mode (absent in the ABA approach) is stable and has a corrected one-loop dispersion relation similar to the other massive modes. Its stability might hold also at the next-to-leading order as we suggest using a unitarity-based argument.
We study the fractional Schr\"odinger equations in $\mathbb R^{1+d}, d \geq 3$ of order ${d}/({d-1}) < \al < 2$. Under the angular regularity assumption we prove linear and nonlinear profile decompositions which extend the previous results \cite{chkl2} to data without radial assumption. As applications we show blowup phenomena of solutions to mass-critical fractional Hartree equations.
The conserved Kardar-Parisi-Zhang equation in the presence of long-range nonlinear interactions is studied by the dynamic renormalization group method. The long-range effect produces new fixed points with continuously varying exponents and gives distinct phase transitions, depending on both the long-range interaction strength and the substrate dimension $d$. The long-range interaction makes the surface width less rough than that of the short-range interaction. In particular, the surface becomes a smooth one with a negative roughness exponent at the physical dimension d=2.
We present the Spitzer MIPS 24 micron source counts in the Extragalactic First Look Survey main, verification and ELAIS-N1 fields. Spitzer's increased sensitivity and efficiency in large areal coverage over previous infrared telescopes, coupled with the enhanced sensitivity of the 24 micron band to sources at intermediate redshift, dramatically improve the quality and statistics of number counts in the mid-infrared. The First Look Survey observations cover areas of, respectively, 4.4, 0.26 and 0.015 sq.deg. and reach 3-sigma depths of 0.11, 0.08 and 0.03 mJy. The extragalactic counts derived for each survey agree remarkably well. The counts can be fitted by a super-Euclidean power law of index alpha=-2.9 from 0.2 to 0.9 mJy, with a flattening of the counts at fluxes fainter than 0.2 mJy. Comparison with infrared galaxy evolution models reveals a peak's displacement in the 24 micron counts. This is probably due to the detection of a new population of galaxies with redshift between 1 and 2, previously unseen in the 15 micron deep counts.
Contribution of simplest loops for hadron-nucleus scattering cross-sections is studied in the Local Reggeon Field Theory with a supercritical pomeron. It is shown that inside the nucleus the supercritical pomeron transforms into a subcritical one, so that perturbative treatment becomes possible. The pomeron intercept becomes complex, which leads to oscillations in the cross-sections.
Bismuth-doped luminescent materials have gained significant attention in the past years owing to their huge potential for the applications in telecommunications, biomedicine, and displays. However, the controlled synthesis of these materials, in particular for those luminescing in the near-infrared (NIR), remains a challenging subject of continuous research effort. Herein, we show that the low-temperature topotactic reduction by using Al metal powders as oxygen getters can be adopted as a powerful technique for the conversion of bismuth-doped red-emitting systems into NIR-emitting cousins as a result of the creation of unique crystalline networks. Thorough experimental characterization indicates that the framework oxygen of hosts can be topotactically extracted, thus producing unique metal-oxygen-metal networks in the reduced phases while preserving the crystalline structure of the precursor. We anticipate that this low-temperature topotactic reduction strategy can be applied to the development of more novel Bi-doped luminescent materials in various forms that can find a broad range of functional applications.
We study the low-temperature physics of the $SU(2)$-symmetric spin-$1/2$ Heisenberg antiferromagnet on a pyrochlore lattice and find fingerprint evidence for the thermal spin-ice state in this frustrated quantum magnet. Our conclusions are based on the results of bold diagrammatic Monte Carlo simulations, with good convergence of the skeleton series down to the temperature $T/J=1/6$. The identification of the spin-ice state is done through a remarkably accurate microscopic correspondence for the static structure factor between the quantum Heisenberg, classical Heisenberg, and Ising models at all accessible temperatures, and the characteristic bowtie pattern with pinch points observed at $T/J=1/6$. The dynamic structure factor at real frequencies (obtained by the analytic continuation of numerical data) is consistent with diffusive spinon dynamics at the pinch points.
Many recent works have been proposed for face image editing by leveraging the latent space of pretrained GANs. However, few attempts have been made to directly apply them to videos, because 1) they do not guarantee temporal consistency, 2) their application is limited by their processing speed on videos, and 3) they cannot accurately encode details of face motion and expression. To this end, we propose a novel network to encode face videos into the latent space of StyleGAN for semantic face video manipulation. Based on the vision transformer, our network reuses the high-resolution portion of the latent vector to enforce temporal consistency. To capture subtle face motions and expressions, we design novel losses that involve sparse facial landmarks and dense 3D face mesh. We have thoroughly evaluated our approach and successfully demonstrated its application to various face video manipulations. Particularly, we propose a novel network for pose/expression control in a 3D coordinate system. Both qualitative and quantitative results have shown that our approach can significantly outperform existing single image methods, while achieving real-time (66 fps) speed.
The convolved Fibonacci numbers F_j^(r) are defined by   (1-z-z^2)^{-r}=\sum_{j>=0}F_{j+1}^(r)z^j. In this note some related numbers that can be expressed in terms of convolved Fibonacci numbers are considered. These numbers appear in the numerical evaluation of a certain number theoretical constant.   This note is a case study of the transform {1/n}\sum_{d|n}mu(d)f(z^d)^{n/d}, with f any formal series and mu the Moebius function), which is studied in a companion paper entitled `The formal series Witt transform'.
We present a mosaic image of the 1.4GHz radio continuum emission from the Large Magellanic Cloud (LMC) observed with the Australia Telescope Compact Array (ATCA) and the Parkes Telescope. The mosaic covers 10.8 x 12.3 square degrees with an angular resolution of 40", corresponding to a spatial scale of 10pc in the LMC. The final image is suitable for studying emission on all scales between 40" and the surveyed area. In this paper, we discuss i) the characteristics of the LMC's diffuse and compact radio continuum emission, ii) the fraction of the emission produced by thermal processes and the implied star formation rate in the LMC, and iii) variations in the radio spectral index across the LMC. Two non-standard reduction techniques that we used to process the ATCA visibility data may be of interest for future wide-field radio continuum surveys. The data are open to the astronomical community and should be a rich resource for studies of individual objects such as supernova remnants, HII regions and planetary nebulae, as well as extended features such as the diffuse emission from synchrotron radiation.
An exact solution of non-BPS multi-walls is found in supersymmetric massive T^\star(\mathbb{CP}^1) model in five dimensions. The non-BPS multi-wall solution is found to have no tachyon. Although it is only metastable under large fluctuations, we can give topological stability by considering a model with a double covering of the T^\star(\mathbb{CP}^1) target manifold. The {\cal N}=1 supersymmetry preserved on the four-dimensional world volume of one wall is broken by the coexistence of the other wall. The supersymmetry breaking is exponentially suppressed as the distance between the walls increases.
We study the geometric bound introduced by Diaconis and Stroock $(1991)$ of the Gibbs sampler for the two-dimensional Ising model with free boundary condition. The obtained result generalizes the method proposed by Shiu and Chen $(2015)$ from dimension one to dimension two. Furthermore we observe that the new bound improves the result given by Ingrassia $(1994)$.
We use a relationship between response and correlation function in nonequilibrium systems to establish a connection between the heat production and the deviations from the equilibrium fluctuation-dissipation theorem. This scheme extends the Harada-Sasa formulation [Phys. Rev. Lett. 95, 130602 (2005)], obtained for Langevin equations in steady states, as it also holds for transient regimes and for discrete jump processes involving small entropic changes. Moreover, a general formulation includes two times and the new concepts of two-time work, kinetic energy, and of a two-time heat exchange that can be related to a nonequilibrium "effective temperature". Numerical simulations of a chain of anharmonic oscillators and of a model for a molecular motor driven by ATP hydrolysis illustrate these points.
The coadjoint orbit method is applied to the construction of Hamiltonian dynamics of massless particles of arbitrary helicity. The unusual transformation properties of canonical variables are interpreted in terms of nonlinear realizations of Poincare group. The action principle is formulated in terms of new space-time variables with standard transformation properties.
We note that it is premature to make a conclusion on the multiplicity of the Pomerons on the basis of the available experimental data since the interactions have a preasymptotic nature
We provide a systematic derivation of boundary layer models in magnetohydrodynamics (MHD), through an asymptotic analysis of the incompressible MHD system. We recover classical linear models, related to the famous Hartmann and Shercliff layers, as well as nonlinear ones, that we call magnetic Prandtl models. We perform their linear stability analysis, emphasizing the stabilizing effect of the magnetic field.
Supernova remnant (SNR) RX J0852.0-4622 is one of the youngest and is most likely the closest among known galactic supernova remnants (SNRs). It was detected in X-rays, the 44Ti gamma-line, and radio. We obtain and analyze medium-resolution spectra of 14 stars in the direction towards the SNR RX J0852.0-4622 in an attempt to detect broad absorption lines of unshocked ejecta against background stars. Spectral synthesis is performed for all the stars in the wavelength range of 3740-4020AA to extract the broad absorption lines of Ca II related to the SNR RX J0852.0-4622. We do not detect any broad absorption line and place a 3-sigma upper limit on the relative depths of <0.04 for the broad Ca II absorption produced by the SNR. We detect narrow low and high velocity absorption components of Ca II. High velocity |V(LSR)|=100-140 km/s components are attributed to radiative shocks in clouds engulfed by the old Vela SNR. The upper limit to the absorption line strength combined with the width and flux of the 44Ti gamma-ray line 1.16 MeV lead us to conclude that SNR RX J0852.0-4622 was probably produced by an energetic SN Ic explosion.
It is shown that graphs that generalize the ADE Dynkin diagrams and have appeared in various contexts of two-dimensional field theory may be regarded in a natural way as encoding the geometry of a root system. After recalling what are the conditions satisfied by these graphs, we define a bilinear form on a root system in terms of the adjacency matrices of these graphs and undertake the study of the group generated by the reflections in the hyperplanes orthogonal to these roots. Some ``non integrally laced " graphs are shown to be associated with subgroups of these reflection groups. The empirical relevance of these graphs in the classification of conformal field theories or in the construction of integrable lattice models is recalled, and the connections with recent developments in the context of ${\cal N}=2$ supersymmetric theories and topological field theories are discussed.
RR Lyrae variable stars have long been reliable standard candles used to discern structure in the Local Group. With this in mind, we present a routine to identify groupings containing a statistically significant number of RR Lyrae variables in the Milky Way environment. RR Lyrae variable groupings, or substructures, with potential Galactic archaeology applications are found using a forest of agglomerative, hierarchical clustering trees, whose leaves are Milky Way RR Lyrae variables. Each grouping is validated by ensuring that the internal RR Lyrae variable proper motions are sufficiently correlated. Photometric information was collected from the Gaia second data release and proper motions from the (early) third data release. After applying this routine to the catalogue of 91234 variables, we are able to report sixteen unique RR Lyrae substructures with physical sizes of less than 1 kpc. Five of these substructures are in close proximity to Milky Way globular clusters with previously known tidal tails and/or a potential connection to Galactic merger events. One candidate substructure is in the neighbourhood of the Large Magellanic Cloud but is more distant (and older) than known satellites of the dwarf galaxy. Our study ends with a discussion of ways in which future surveys could be applied to the discovery of Milky Way stellar streams.
In supergravity compactifications, there is in general no clear prescription on how to select a finite-dimensional family of metrics on the internal space, and a family of forms on which to expand the various potentials, such that the lower-dimensional effective theory is supersymmetric. We propose a finite-dimensional family of deformations for regular Sasaki-Einstein seven-manifolds $M_7$, relevant for M-theory compactifications down to four dimensions. It consists of integrable Cauchy-Riemann structures, corresponding to complex deformations of the Calabi-Yau cone $M_8$ over $M_7$. The non-harmonic forms we propose are the ones contained in one of the Kohn-Rossi cohomology groups, which is finite-dimensional and naturally controls the deformations of Cauchy-Riemann structures. The same family of deformations can be also described in terms of twisted cohomology of the base $M_6$, or in terms of Milnor cycles arising in deformations of $M_8$. Using existing results on SU(3) structure compactifications, we briefly discuss the reduction of M-theory on our class of deformed Sasaki-Einstein manifolds to four-dimensional gauged supergravity.
We outline a general approach to the computation of transport properties of interacting systems at low temperetures and frequencies. We show that if the fixed point and the irrelevant operators around it are known, then by studying the structure of the softly violated conserved currents chracterizing the fixed point one may set up an effective calculation in terms of a memory matrix formalism. We apply this approach to the computation of thermal conductivity of spin chains embedded in a matter matrix and interacting with its phonons. The results are found to be in very good agreement with experiment.
In the present contribution we discuss the role of experimental limitations in the classical limit problem. We studied some simple models and found that Quantum Mechanics does not re-produce classical mechanical predictions, unless we consider the experimental limitations ruled by uncertainty principle. We have shown that the discrete nature of energy levels of integrable systems can be accessed by classical measurements. We have defined a precise limit for this procedure. It may be used as a tool to define the classical limit as far as the discrete spectra of integrable systems are concerned.
In a power spectrum of the Sun's acoustic waves, the p modes have distinctly skewed frequency profiles. Furthermore, the asymmetry is observed to have the opposite sign in power spectra made from line-of-sight velocity and continuum intensity. The asymmetry and its reversal in sign has previously been explained using a combination of mechanisms that involve the acoustic source. A localized acoustic source within an acoustic cavity naturally generates asymmetric profiles through wave interference; however, the sign of the asymmetry due to this mechanism is identical for all observables. The reversal of the asymmetry between velocity and intensity observations has been attributed to the visibility of the source itself (i.e., "correlated noise"). In this paper, I will show that asymmetry generated by a localized source can be interpreted as either a wave interference effect in physical space, or a mode interference effect in spectral space. I advocate a new mode-fitting procedure based on this new interpretation, whereby the complex phases of all the modes determine the mode asymmetries. Further, I suggest that information about the acoustic source function is encapsulated in the amplitude of each mode, and present a scheme by which the source function can be obtained from measured mode amplitudes by standard helioseismic inversion techniques.
We present a model for typical charged defects in weakly doped Y1-xCaxVO3 perovskites and study how they influence the magnetic and orbital order. Starting from a multiband Hubbard model, we show that the charge carriers introduced by doping are bound to the Ca defects with large binding energy of about 1 eV at small doping, and give rise to the in-gap absorption band observed in the optical spectroscopy. The central position of a generic Ca defect with eight equidistant vanadium neighbors implies a partly filled defect band and permits activated transport due to Coulomb disorder. We explore the effect of bound charge carriers on the dynamics of the (yz,zx) orbital and spin degrees of freedom in the context of a spin-orbital t-J model. After deriving the superexchange interactions around the doped hole, we show that the transition from G-type to C-type antiferromagnetic (AF) order is triggered by the kinetic energy of doped holes via the double-exchange mechanism. The defect states lead to local modification of orbital correlations within ferromagnetic chains along the c axis; some of them contain hole defects, while the charge-orbital coupling suppresses locally (yz,zx) orbital fluctuations in the others. Thereby, Ca defects provide a physical mechanism for spin-orbital dimerization along the ferromagnetic bonds, suggesting that, in the C-AF phase of weakly doped Y1-xCaxVO3, dimerization increases with doping.
This paper gives a priori estimates for the positve solutions of Kirchhoff type equation without variational structure.