ShantanuT01/DACTYL-Pretraining huggingface dataset:
Context. We carry out a detailed 2D study of the ionised gas in the local universe galaxy UGC9837. In nearby galaxies, like the galaxy in question here, the spatial distribution of the physical properties can be studied in detail, providing benchmarks for galaxy formation models.   Aims. Our aim is to derive detailed and spatially resolved physical properties of the ionised gas of UGC 9837. In addition, we derive an integrated spectrum of the galaxy and study how varying spatial coverage affects the derived integrated properties. We also study how the same properties would be seen if the galaxy was placed at a higher redshift and observed as part of one of the high-z surveys.   Methods. UGC9837 was observed using the PMAS PPAK integral field unit. The spectra are reduced and calibrated and the stellar and ionised components separated. Using strong emission line ratios of the ionised gas, the source of ionisation, the dust extinction, the star formation rate, the electron density and the oxygen abundance derived from a total integrated spectrum, central integrated spectrum and individual fibre spectra are studied. Finally, the same properties are studied in a spectrum whose spatial resolution is degraded to simulate high-z observations.   Results. The spatial distribution of the ionised gas properties is consistent with inside-out growing scenario of galaxies. We also find that lack of spatial coverage would bias the results derived from the integrated spectrum leading, e.g., to an under-estimation of ionisation and over-estimation of metallicity, if only the centre of the galaxy was covered by the spectrum. Our simulation of high-z observations shows that part of the spatial information, such as dust and SFR distribution would be lost while shallower gradients in metallicity and ionisation strength would be detected.
We study the electrical and thermal transport through the SU(N) Wolff model with the use of bosonization. The Wilson ratio reaches unity as N grows to infinity. The electric conductance is dominated by the charge channel, and decreases monotonically with increasing interaction. The thermal conductivity enhances in the presence of local Hubbard U. The Wiedemann-Franz law is violated, the Lorentz number depends strongly on the interaction parameter, which can be regarded as a manifestation of spin-charge separation.
The present work deals with the dynamics of radiating star which is considered to be expansion free cylindrical symmetric dust dissipative fluids. Several treatments are adopted for the description of geometrical and physical features of such stars. Firstly, it is shown that, the dynamical star does not permit the streaming out limit and diffusion approximation and also proved that acceleration and dissipation are necessary for its dynamical evolution. It has also shown that, a static expansion free cylinder must be non-radiating. Secondly, the existence of cavity model and self-similar solution for the such dynamical star are also investigated.
There is currently a great need for solid state lasers that emit in the infrared, as this is the operating wavelength regime for applications in telecommunications. Existing $\pi$--conjugated polymers all emit in the visible or ultraviolet, and whether or not $\pi$--conjugated polymers that emit in the infrared can be designed is an interesting challenge. On the one hand, the excited state ordering in trans-polyacetylene, the $\pi$--conjugated polymer with relatively small optical gap, is not conducive to light emission because of electron-electron interaction effects. On the other hand, excited state ordering opposite to that in trans-polyacetylene is usually obtained by chemical modification that increases the effective bond-alternation, which in turn increases the optical gap. We develop a theory of electron correlation effects in a model $\pi$-conjugated polymer that is obtained by replacing the hydrogen atoms of trans-polyacetylene with transverse conjugated groups, and show that the effective on-site correlation in this system is smaller than the bare correlation in the unsubstituted system. An optical gap in the infrared as well as excited state ordering conducive to light emission is thereby predicted upon similar structural modifications.
We propose to use the Kolmogorov-Smirnov test to uncover non-statistical differences between events created in heavy ion collisions within the same centrality class. The advantage of the method over other approaches which are currently in use, is that it is sensitive to any difference between the events and is not restricted to simple moments of the distribution of hadrons. The particular application examined here is the identification of the fireball decay due to spinodal fragmentation and/or sudden rise of the bulk viscosity.
Migration of oxygen vacancies has been proposed to play an important role in the bipolar memristive behaviors since oxygen vacancies can directly determine the local conductivity in many systems. However, a recent theoretical work demonstrated that both migration of oxygen vacancies and coexistence of cation and anion vacancies are crucial to the occurrence of bipolar memristive switching, normally observed in the small-sized NiO. So far, experimental work addressing this issue is still lacking. In this work, with conductive atomic force microscope and combined scanning transmission electron microscopy & electron energy loss spectroscopy, we reveal that concentration surplus of Ni vacancy over O vacancy determines the bipolar memristive switching of NiO films. Our work supports the dual-defects-based model, which is of fundamental importance for understanding the memristor mechanisms beyond the well-established oxygen-vacancy-based model. Moreover, this work provides a methodology to investigate the effect of dual defects on memristive behaviors.
We review the analytical prescriptions in the literature to model the 21-cm (emission line surveys/intensity mapping experiments) and Damped Lyman-Alpha (DLA) observations of neutral hydrogen (HI) in the post-reionization universe. While these two sets of prescriptions have typically been applied separately for the two probes, we attempt to connect these approaches to explore the consequences for the distribution and evolution of HI across redshifts. We find that a physically motivated, 21-cm based prescription, extended to account for the DLA observables provides a good fit to the majority of the available data, but cannot accommodate the recent measurement of the clustering of DLAs at $z \sim 2.3$. This highlights a tension between the DLA bias and the 21-cm measurements, unless there is a very significant change in the nature of HI-bearing systems across redshifts 0-3. We discuss the implications of our findings for the characteristic host halo masses of the DLAs and the power spectrum of 21-cm intensity fluctuations.
We present a numerical evidence supporting the claim that the mass-dependent transitions of the halo spin orientations from the intermediate to the minor principal directions of the local tidal fields can in principle be a useful discriminator of dark energy models. We first define a spin transition zone as the mass range of the halos, $\Delta m_{t}$, for which the intrinsic spin alignments with the minor tidal principal directions become as strong as that with the intermediate principal directions. Then, utilizing the halo samples from the DEUS simulations performed separately for the WMAP7 $\Lambda$CDM, phantom DE and quintessence models, we investigate if and how the three different dark energy models differ in $\Delta m_{t}$. It is shown that the differences in $\Delta m_{t}$ among the three dark energy models are significant enough to discriminate the models from one another and robust against the variations of the smoothing scale of the tidal field and redshift. Noting that a narrower spin transition zone is more powerful as a probe of dark energy, we also show that the spin transition zones become narrower at higher redshifts, in the filamentary environments and for the case that the tidal fields are smoothed on the smaller scales. Our result is consistent with the scenario that $\Delta m_{t}$ is mainly determined by how fast the nonlinear evolution of the tidal field proceeds, which in turn sensitively depends on the background cosmology.
We produce for each natural number $n \geq 3$ two 1--parameter families of Riemann surfaces admitting automorphism groups with two cyclic subgroups $H_{1}$ and $H_{2}$ of orden $2^{n}$, that are conjugate in the group of orientation--preserving homeomorphism of the corresponding Riemann surfaces, but not conjugate in the group of conformal automorphisms.   This property implies that the subvariety $\mathcal{M}_{g}(H_{1})$ of the moduli space $\mathcal{M}_{g}$ consisting of the points representing the Riemann surfaces of genus $g$ admitting a group of automorphisms topologically conjugate to $H_{1} $ (equivalently to $H_{2}$) is not a normal subvariety.
We report on the wide band spectra of SN 1006 as observed by Suzaku. Thermal and nonthermal emission are successfully resolved thanks to the excellent spectral response of Suzaku's X-ray CCD XIS. The nonthermal emission cannot be reproduced by a simple power-law model but needs a roll-off at 5.7$\times 10^{16}$ Hz = 0.23 keV. The roll-off frequency is significantly higher in the northeastern rim than in the southwestern rim. We also have placed the most stringent upper limit of the flux above 10 keV using the Hard X-ray Detector.
Quantum networks offer a unifying set of opportunities and challenges across exciting intellectual and technical frontiers, including for quantum computation, communication, and metrology. The realization of quantum networks composed of many nodes and channels requires new scientific capabilities for the generation and characterization of quantum coherence and entanglement. Fundamental to this endeavor are quantum interconnects that convert quantum states from one physical system to those of another in a reversible fashion. Such quantum connectivity for networks can be achieved by optical interactions of single photons and atoms, thereby enabling entanglement distribution and quantum teleportation between nodes.
Although most fundamental laws are invariant under time reversal, experience exhibits the presence of irreversible phenomena -- the arrows of time. Their origin lies in cosmology, and I argue that only quantum cosmology can provide the appropriate formal framework. After briefly reviewing the formalism, I discuss how a simple and natural boundary condition can lead to the observed arrows of time. This yields at the same time interesting consequences for black holes.
In this paper, our goal is to improve the local well-posedness theory for certain generalized Boussinesq equations by revisiting bilinear estimates related to the Schr\"{o}dinger equation. Moreover, we propose a novel, automated procedure to handle the summation argument for these bounds.
Motivated by recent experimental work of Burd et al., we propose a model of bi-directional ant-traffic on pre-existing ant-trails. It captures in a simple way some of the generic collective features of movements of real ants on a trail. Analyzing this model, we demonstrate that there are crucial qualitative differences between vehicular- and ant-traffics. In particular, we predict some unusual features of the flow rate that can be tested experimentally. As in the uni-directional model a non-monotonic density-dependence of the average velocity can be observed in certain parameter regimes. As a consequence of the interaction between oppositely moving ants the flow rate can become approximately constant over some density interval.
Quantum error correction (QEC) and fault-tolerant quantum computation represent one of the most vital theoretical aspect of quantum information processing. It was well known from the early developments of this exciting field that the fragility of coherent quantum systems would be a catastrophic obstacle to the development of large scale quantum computers. The introduction of quantum error correction in 1995 showed that active techniques could be employed to mitigate this fatal problem. However, quantum error correction and fault-tolerant computation is now a much larger field and many new codes, techniques, and methodologies have been developed to implement error correction for large scale quantum algorithms. In response, we have attempted to summarize the basic aspects of quantum error correction and fault-tolerance, not as a detailed guide, but rather as a basic introduction. This development in this area has been so pronounced that many in the field of quantum information, specifically researchers who are new to quantum information or people focused on the many other important issues in quantum computation, have found it difficult to keep up with the general formalisms and methodologies employed in this area. Rather than introducing these concepts from a rigorous mathematical and computer science framework, we instead examine error correction and fault-tolerance largely through detailed examples, which are more relevant to experimentalists today and in the near future.
We revisit in a probabilistic framework the umbral approach of Bernoulli, Euler and Carlitz Hermite polynomials by Gessel [1].
The content of this paper is incorporated into hep-th/9805093
In this paper, we define a generalization of the Brauer groups by using Bloch's cycle complex on etale site. We prove the Gersten conjecture of generalized Brauer group on some cases. As an application we prove the Gersten conjecture of the logarithmic Hodge-Witt cohomology for a two dimensional regular local ring which is smooth over a spectrum of some discrete valuation ring of characteristic $p>0$. Moreover we consider a generalization of Artin's theorem on Brauer groups.
Given a parametrisation of an elliptic curve over Q by a Shimura curve, we show that the images of almost all Heegner points are of infinite order. For parametrisations of elliptic curves by modular curves this was proven earlier by Nekovar and Schappacher by a different method.
In this paper, a novel neural network architecture is proposed attempting to rectify text images with mild assumptions. A new dataset of text images is collected to verify our model and open to public. We explored the capability of deep neural network in learning geometric transformation and found the model could segment the text image without explicit supervised segmentation information. Experiments show the architecture proposed can restore planar transformations with wonderful robustness and effectiveness.
Sn-doped In$_2$O$_3$ or ITO is the most widely used transparent conducting oxide. We use first-principles calculations to investigate the limitations to its transparency due to free-carrier absorption mediated by phonons or charged defects. We find that the main contribution to the phonon-assisted indirect absorption is due to emission (as opposed to absorption) of phonons, which explains why the process is relatively insensitive to temperature. The wavelength dependence of this indirect absorption process can be described by a power law. Indirect absorption mediated by charged defects or impurities is also unavoidable since doping is required to obtain conductivity. At high carrier concentrations, screening by the free carriers becomes important. We find that charged-impurity-assisted absorption becomes larger than phonon-assisted absorption for impurity concentrations above 10$^{20}$ cm$^{-3}$. The differences in the photon-energy dependence of the two processes can be explained by band-structure effects.
The Pauli--Villars (PV) regularization scheme is applied to a calculation of the dressed-electron state and its anomalous magnetic moment in light-front-quantized quantum electrodynamics (QED) in Feynman gauge. The regularization is provided by heavy, negative-metric fields added to the Lagrangian. The light-front QED Hamiltonian then leads to a well-defined eigenvalue problem for the dressed-electron state expressed as a Fock-state expansion. The Fock-state wave functions satisfy coupled integral equations that come from this eigenproblem. A finite system of equations is obtained by truncation to no more than two photons and no positrons; this extends earlier work that was limited to dressing by a single photon. Numerical techniques are applied to solve the coupled system and compute the anomalous moment, for which we obtain agreement with experiment, within numerical errors, but observe a small systematic discrepancy that should be due to the absence of electron-positron loops and of three-photon self-energy effects. We also discuss the prospects for application of the method to quantum chromodynamics.
The purely nonperturbative soft contribution to the $\gamma^* p \to \Delta^+$ transition form factors is estimated using the local quark-hadron duality approach. Our results show that the soft contribution is dominated by the magnetic transition: the ratio $G_E^*(Q^2)/G_M^*(Q^2)$ is small for all accessible $Q^2$, in contrast to pQCD expectations that $G_E^*(Q^2) \to -G_M^*(Q^2)$. We also found that the soft contribution to the magnetic form factor is large enough to explain the magnitude of existing experimental data.
Singularities in macroscopic systems at discontinuous phase transitions are replaced in finite systems by sharp but continuous changes. Both the energy differences between metastable and stable phases and the energy barriers separating these phases decrease with decreasing particle number. Then, for small enough systems, random heterophasic oscillations of the entire system become an observable form of thermal motion. Under certain conditions, these oscillations take the form of oscillatory nucleation. We discuss mechanisms and observation conditions for these random transitions between phases.
Consider the interchange process on a connected graph $G=(V,E)$ on $n$ vertices. I.e.\ shuffle a deck of cards by first placing one card at each vertex of $G$ in a fixed order and then at each tick of the clock, picking an edge uniformly at random and switching the two cards at the end vertices of the edge with probability 1/2. Well known special cases are the random transpositions shuffle, where $G$ is the complete graph, and the transposing neighbors shuffle, where $G$ is the $n$-path. Other cases that have been studied are the $d$-dimensional grid, the hypercube, lollipop graphs and Erd\H os-R\'enyi random graphs above the threshold for connectedness.   In this paper the problem is studied for general $G$. Special attention is focused on trees, random trees and the giant component of critical and supercritical $G(N,p)$ random graphs. Upper and lower bounds on the mixing time are given. In many of the cases, we establish the exact order of the mixing time. We also mention the cases when $G$ is the hypercube and when $G$ is a bounded-degree expander, giving upper and lower bounds on the mixing time.
Optical reflection microscopy is one of the main imaging tools to visualize graphene microstructures. Here is reported a novel method that employs refractive index optimization in an optical reflection microscope, which greatly improves the visibility of graphene flakes. To this end, an immersion liquid with a refractive index that is close to that of the glass support is used in-between the microscope lens and the support improving the contrast and resolution of the sample image. Results show that the contrast of single and few layer graphene crystals and structures can be enhanced by a factor of 4 compared to values commonly achieved with transparent substrates using optical reflection microscopy lacking refractive index optimization.
The properties of Dirac electrons in a magnetic superlattice (SL) on graphene consisting of very high and thin (delta-function) barriers are investigated. We obtain the energy spectrum analytically and study the transmission through a finite number of barriers. The results are contrasted with those for electrons described by the Schrodinger equation. In addition, a collimation of an incident beam of electrons is obtained along the direction perpendicular to that of the SL. We also highlight the analogy with optical media in which the refractive index varies in space.
The formation of unusually shaped Stokes V profiles of the Fe I 630.2 nm line in the solar photosphere are investigated. The results of numerical 2-D MHD simulation of solar magnetogranulation are used for this. In their properties, the synthetic unusual profiles with extremely asymmetry are similar to the unusual profiles observed with a spatial resolution better than 1" in the network and internetwork regions. According to our results the unusual profiles mostly appear in clusters along the polarity inversion lines in the regions of weak magnetic fields with mixed polarity. As a rule, they are located at the edges of granules and lanes, and sometimes they are met close to strong magnetic field concentrations with high velocity and magnetic field strength gradients. They turned out to appear as clusters in the regions where large granules disintegrate and new magnetic flux tubes begin to form. The unusual $V$ profiles may have from one to six lobes. The one-lobe and multilobe profiles are of the same origin. The processing causing the extreme asymmetry of the profiles are characterized by one or several polarity reversal along the line of sight as well as by complicated velocity and field strength gradients. The greater the number of profile lobes, the greater is the probability of the field gradient sign change. Hence it follows that the magnetic field should be very complicated in the regions of formation of extremely asymmetric $V$ profiles. This is confirmed by immediate results of MHD granulation simulations, which demonstrate the formation of vortices and turbulence by the velocity shear at down draft edges. These processes add complexity to the magnetic field structure by mixing field polarities, particularly at the edges of granules.
We propose a Paired Few-shot GAN (PFS-GAN) model for learning generators with sufficient source data and a few target data. While generative model learning typically needs large-scale training data, our PFS-GAN not only uses the concept of few-shot learning but also domain shift to transfer the knowledge across domains, which alleviates the issue of obtaining low-quality generator when only trained with target domain data. The cross-domain datasets are assumed to have two properties: (1) each target-domain sample has its source-domain correspondence and (2) two domains share similar content information but different appearance. Our PFS-GAN aims to learn the disentangled representation from images, which composed of domain-invariant content features and domain-specific appearance features. Furthermore, a relation loss is introduced on the content features while shifting the appearance features to increase the structural diversity. Extensive experiments show that our method has better quantitative and qualitative results on the generated target-domain data with higher diversity in comparison to several baselines.
We introduce a three-parameter family of up-down ordered Chinese restaurant processes ${\rm PCRP}^{(\alpha)}(\theta_1,\theta_2)$, $\alpha\in(0,1)$, $\theta_1,\theta_2\ge 0$, generalising the two-parameter family of Rogers and Winkel. Our main result establishes self-similar diffusion limits, ${\rm SSIP}^{(\alpha)}(\theta_1,\theta_2)$-evolutions generalising existing families of interval partition evolutions. We use the scaling limit approach to extend stationarity results to the full three-parameter family, identifying an extended family of Poisson--Dirichlet interval partitions. Their ranked sequence of interval lengths has Poisson--Dirichlet distribution with parameters $\alpha\in(0,1)$ and $\theta:=\theta_1+\theta_2-\alpha\ge-\alpha$, including for the first time the usual range of $\theta>-\alpha$ rather than being restricted to $\theta\ge 0$. This has applications to Fleming--Viot processes, nested interval partition evolutions and tree-valued Markov processes, notably relying on the extended parameter range.