ShantanuT01/DACTYL-Pretraining huggingface dataset:
We show that conductance of 1D channel with one point-like impurity critically depends on asymptotic behavior of e-e interaction at small momenta k (about inverse length of a channel). Conductance reemerges (contrary to the case of point-like repulsive potential) if potential V(k=0)= 0. For example, this happens if the bare e-e interaction is screened by the charges in the bulk. The relation of this phenomena to the long-range order present in the Luttinger model is discussed.
Recent experiments showed that non-uniform strain can be produced by depositing graphene over pillars. We employed atomistic calculations to study the non-uniform strain and the induced pseudo-magnetic field up to 5000 Tesla in graphene on top of nano-pillars. By decreasing the distance between the nano-pillars a complex distribution for the pseudo-magnetic field can be generated. Furthermore, we performed tight-binding calculations of the local density of states (LDOS) by using the relaxed graphene configuration obtained from the atomistic calculations. We find that the quasiparticle LDOS are strongly modified near the pillars, both at low energies showing sub-lattice polarization, and at high energies showing shifts of the van Hove singularity. Our study shows that changing the specific pattern of the nano-pillars allows us to create a desired shape of the pseudo-magnetic field profile while the LDOS maps provide an input for experimental verifications by scanning tunneling microscopy.
In this paper, we consider a simplified error-correcting problem: for a fixed encoding process, to find a cascade connected quantum channel such that the worst fidelity between the input and the output becomes maximum. With the use of the one-to-one parametrization of quantum channels, a procedure finding a suboptimal error-correcting channel based on a semidefinite programming is proposed. The effectiveness of our method is verified by an example of the bit-flip channel decoding.
Automatically recognizing activities in video is a classic problem in vision and helps to understand behaviors, describe scenes and detect anomalies. We propose an unsupervised method for such purposes. Given video data, we discover recurring activity patterns that appear, peak, wane and disappear over time. By using non-parametric Bayesian methods, we learn coupled spatial and temporal patterns with minimum prior knowledge. To model the temporal changes of patterns, previous works compute Markovian progressions or locally continuous motifs whereas we model time in a globally continuous and non-Markovian way. Visually, the patterns depict flows of major activities. Temporally, each pattern has its own unique appearance-disappearance cycles. To compute compact pattern representations, we also propose a hybrid sampling method. By combining these patterns with detailed environment information, we interpret the semantics of activities and report anomalies. Also, our method fits data better and detects anomalies that were difficult to detect previously.
NGC 7789 is an intermediate-age open cluster with an age that is similar to the mean age of contact binary stars. V12 is a bright UMa-type binary star with an orbital period of 0.397 day. The first complete light curves of V12 in V, R, and I bands are presented and analyzed with the W-D (Wilson and Devinney) method. The results shows that V12 is an intermediate-contact binary (f = 43%) with a mass ratio of 3.848, and it is a W-type contact binary where the less massive component is slightly hotter than the more massive one. The asymmetries of the light curves are explained by the presence of a dark spot on the more massive component. The derived orbital inclination (i = 83.6o) indicates that it is a total eclipsing binary, which suggests that the determined parameters are reliable. The orbital period may show a long-term increase at a rate of P = +2.48 x 10-6 days/year that reveals a rapid mass transfer from the less massive component to the more massive one. However, more observations are needed to confirm this conclusion. The presence of an intermediate-contact binary in an intermediate-age open cluster may suggest that some contact binaries have a very short pre-contact timescale. The presence of a third body or/and stellar collision may help to shorten the pre-contact evolution.
We present direct measurements of cubic bias parameters of dark matter halos from the halo-matter-matter-matter trispectrum. We measure this statistic efficiently by cross-correlating the halo field measured in N-body simulations with specific third-order nonlocal transformations of the initial density field in the same simulation. Together with the recent Abidi & Baldauf (2018), these are the first measurements of halo bias using the four-point function that have been reported to date. We also obtain constraints on the quadratic bias parameters. For all individual cubic parameters involving the tidal field $\mathcal{K}_{ij}$, we find broad consistency with the prediction of the Lagrangian local-in-matter-density ansatz, with some indications of a positive Lagrangian coefficient $b_{\rm td}^L$ multiplying the time derivative of $\mathcal{K}_{ij}$. For the quadratic tidal bias ($b_{K^2}$), we obtain a significant detection of a negative Lagrangian tidal bias.
We prove existence and uniqueness of solutions to the initial-boundary value problem for the Lifshitz--Slyozov equation (a nonlinear transport equation on the half-line), focusing on the case of kinetic rates with unbounded derivative at the origin. Our theory covers in particular those cases with rates behaving as power laws at the origin, for which an inflow behavior is expected and a boundary condition describing nucleation phenomena needs to be imposed. The method we introduce here to prove existence is based on a formulation in terms of characteristics, with a careful analysis on the behavior near the singular boundary. As a byproduct we provide a general theory for linear continuity equations on a half-line with transport fields that degenerate at the boundary. We also address both the maximality and the uniqueness of inflow solutions to the Lifshitz--Slyozov model, exploiting monotonicity properties of the associated transport equation.
We study the generalized eigenvalue problem in $\mathbb{R}^N$ for a general convex nonlinear elliptic operator which is locally elliptic and positively $1$-homogeneous. Generalizing article of Berestycki and Rossi in [Comm. Pure Appl. Math. 68 (2015), no. 6, 1014-1065] we consider three different notions of generalized eigenvalues and compare them. We also discuss the maximum principles and uniqueness of principal eigenfunctions.
We introduce a new outdoor urban 3D pointcloud dataset, covering a total area of 2.7 $km^2$, sampled from three Swiss cities with different characteristics. The dataset is manually annotated for semantic segmentation with per-point labels, and is built using photogrammetry from images acquired by multirotors equipped with high-resolution cameras. In contrast to datasets acquired with ground LiDAR sensors, the resulting point clouds are uniformly dense and complete, and are useful to disparate applications, including autonomous driving, gaming and smart city planning. As a benchmark, we report quantitative results of PointNet++, an established point-based deep 3D semantic segmentation model; on this model, we additionally study the impact of using different cities for model generalization.
Zeckendorf proved that every positive integer $n$ can be written uniquely as the sum of non-adjacent Fibonacci numbers; a similar result holds for other positive linear recurrence sequences. These legal decompositions can be used to construct a game that starts with a fixed integer $n$, and players take turns using moves relating to a given recurrence relation. The game eventually terminates in a unique legal decomposition, and the player who makes the final move wins.   For the Fibonacci game, Player $2$ has the winning strategy for all $n>2$. We give a non-constructive proof that for the two-player $(c, k)$-nacci game, for all $k$ and sufficiently large $n$, Player $1$ has a winning strategy when $c$ is even and Player $2$ has a winning strategy when $c$ is odd. Interestingly, the player with the winning strategy can make a mistake as early as the $c + 1$ turn, in which case the other player gains the winning strategy. Furthermore, we proved that for the $(c, k)$-nacci game with players $p \ge c + 2$, no player has a winning strategy for any $n \ge 3c^2 + 6c + 3$. We find a stricter lower boundary, $n \ge 7$, in the case of the three-player $(1, 2)$-nacci game. Then we extend the result from the multiplayer game to multialliance games, showing which alliance has a winning strategy or when no winning strategy exists for some special cases of multialliance games.
With the increasing interest for the control of the system at the nano and mesoscopic scales, studies have been focused on the limit of the energy dissipation in an open system by refining the concept of the Maxwell's demon. The well-known Sagawa-Ueda fluctuation theorem provides an explanation of the demon: the absence of a part of demon's information leads to an improper entropy production which violates the thermodynamic 2nd law. Realizing that the demon contributes not only to the system but also to the environments, we introduce the dissipative information to quantify the total contribution of the demon, rather than using an improper entropy production. We prove a set of new fluctuation theorems based on this, which can be used to uncover the truth behind the demon: The controlled system does not violate the 2nd law at any coarse-grained level for the demon's control. However, there exists an inevitable demon-induced dissipative information which always increases the entropy production. A consequence of these theorems is that, less work and more heat can be extracted and generated respectively by a demon than the limits predicted by the Ueda-Sagawa theorem. We also suggest a possible realization of the experimental estimation of these work and heat bounds, which can be measured and tested.
We investigate the existence of solutions $E:\mathbb{R}^3\to\mathbb{R}^3$ of the time-harmonic semilinear Maxwell equation $$\nabla\times(\nabla\times E) + V(x) E = \partial_E F(x,E) \quad \text{in}\mathbb{R}^3,$$ where $V:\mathbb{R}^3\to\mathbb{R}$, $V(x)\leq 0$ a.e. on $\mathbb{R}^3$, $\nabla\times$ denotes the curl operator in $\mathbb{R}^3$ and $F:\mathbb{R}^3\times\mathbb{R}^3\to\mathbb{R}$ is a nonlinear function in $E$. In particular we find a ground state solution provided that suitable growth conditions on $F$ are imposed and $L^{3/2}$-norm of $V$ is less than the best Sobolev constant. In applications $F$ is responsible for the nonlinear polarization and $V(x)=-\mu\omega^2\varepsilon(x)$ where $\mu>0$ is the magnetic permeability, $\omega$ is the frequency of the time-harmonic electric field $\Re\{E(x)e^{i\omega t}\}$ and $\varepsilon$ is the linear part of the permittivity in an inhomogeneous medium.
We consider a noncommutative (NC) inflationary model with a homogeneous scalar field minimally coupled to gravity. The particular NC inflationary setting produces entirely new consequences. We first analyze the free field case and subsequently examine the situation where the scalar field is subjected to a polynomial and exponential potentials. We propose to use a canonical deformation between momenta, in a spatially flat FLRW universe, and while the Friedmann equation remains unaffected the Friedmann acceleration equation (and thus the Klein-Gordon equation) is modified by an extra term linear in the NC parameter. This concrete noncommutativity on the momenta allows interesting dynamics that other NC models seem not to allow. Let us be more precise. This extra term behaves as the sole explicit pressure that under the right circumstances implies a period of accelerated expansion of the universe. We find that in the absence of the scalar field potential, and in contrast with the commutative case, in which the scale factor always decelerates, we obtain an inflationary phase for small negative values of the NC parameter. Subsequently, the period of accelerated expansion is smoothly replaced by an appropriate deceleration phase providing an interesting model regarding the graceful exit problem in inflationary models.   Moreover, in the case of the free scalar field, we show that not only the horizon problem is solved but also there is some resemblance between the evolution equation of the scale factor associated to our model and that for the $R^2$ (Starobinsky) inflationary model. Therefore, our herein NC model not only can be taken as an appropriate scenario to get a successful kinetic inflation, but also is a convenient setting to obtain inflationary universe possessing the graceful exit when scalar field potentials are present.
Temporal action proposal generation (TAPG) is a challenging task, which requires localizing action intervals in an untrimmed video. Intuitively, we as humans, perceive an action through the interactions between actors, relevant objects, and the surrounding environment. Despite the significant progress of TAPG, a vast majority of existing methods ignore the aforementioned principle of the human perceiving process by applying a backbone network into a given video as a black-box. In this paper, we propose to model these interactions with a multi-modal representation network, namely, Actors-Objects-Environment Interaction Network (AOE-Net). Our AOE-Net consists of two modules, i.e., perception-based multi-modal representation (PMR) and boundary-matching module (BMM). Additionally, we introduce adaptive attention mechanism (AAM) in PMR to focus only on main actors (or relevant objects) and model the relationships among them. PMR module represents each video snippet by a visual-linguistic feature, in which main actors and surrounding environment are represented by visual information, whereas relevant objects are depicted by linguistic features through an image-text model. BMM module processes the sequence of visual-linguistic features as its input and generates action proposals. Comprehensive experiments and extensive ablation studies on ActivityNet-1.3 and THUMOS-14 datasets show that our proposed AOE-Net outperforms previous state-of-the-art methods with remarkable performance and generalization for both TAPG and temporal action detection. To prove the robustness and effectiveness of AOE-Net, we further conduct an ablation study on egocentric videos, i.e. EPIC-KITCHENS 100 dataset. Source code is available upon acceptance.
Time-decaying harmonic oscillators yield dispersive estimates with weak decay, and change the threshold power of the nonlinearity between the short and the long range. In the non-critical case for the time-decaying harmonic oscillator, this threshold can be characterized by polynomial nonlinearities. However, in the critical case, it is difficult to characterize the threshold using only polynomial terms, and thus we use logarithmic nonlinear terms.
Using the real-time diagrammatic technique and taking into account both the sequential and cotunneling processes, we analyze the transport properties of single-wall metallic carbon nanotubes coupled to nonmagnetic and ferromagnetic leads in the full range of parameters. In particular, considering the two different shell filling schemes of the nanotubes, we discuss the behavior of the differential conductance, tunnel magnetoresistance and the shot noise. We show that in the Coulomb diamonds corresponding to even occupations, the shot noise becomes super-Poissonian due to bunching of fast tunneling processes resulting from the dynamical channel blockade, whereas in the other diamonds the noise is roughly Poissonian, in agreement with recent experiments. The tunnel magnetoresistance is very sensitive to the number of electrons in the nanotube and exhibits a distinctively different behavior depending on the shell filling sequence of the nanotube.
Thermonuclear (type-I) X-ray bursts, observed from neutron star (NS) low-mass X-ray binaries (LMXB), provide constraints on NS masses and radii and consequently the equation of state of NS cores. In such analyses various assumptions are made without knowing if they are justified. We have analyzed X-ray burst spectra from the LMXB 4U 1608-52, with the aim of studying how the different persistent emission components react to the bursts. During some bursts in the soft spectral state we find that there are two variable components; one corresponding to the burst blackbody component and another optically thick Comptonized component. We interpret the latter as the spreading layer between the NS surface and the accretion disc, which is not present during the hard state bursts. We propose that the spectral changes during the soft state bursts are driven by the spreading layer that could cover almost the entire NS in the brightest phases due to the enhanced radiation pressure support provided by the burst, and that the layer subsequently returns to its original state during the burst decay. When deriving the NS mass and radius using the soft state bursts two assumptions are therefore not met: the NS is not entirely visible and the burst emission is reprocessed in the spreading layer, causing distortions of the emitted spectrum. For these reasons the NS mass and radius constraints using the soft state bursts are different compared to the ones derived using the hard state bursts.
We present a complete systematic theoretical study of multifragmentation for asymmetric colliding nuclei for heavy-ion reactions in the energy range between 50 MeV/nucleon and 1000 MeV/nucleon by using isospin dependent quantum molecular dynamics (IQMD) model. We have observed an interesting outcome for asymmetric colliding nuclei. The comparison between the symmetric and asymmetric colliding nuclei for the isospin independent cross section and isospin dependent cross section has been studied. We have found the pronounced effect of different cross section and mass asymmetry on the nuclear reaction dynamics.
The structure and magnetic properties of nanocrystalline PrCo$_3$ prepared by high-energy milling technique have been investigated by means of X-ray diffraction using the Rietveld method coupled to Curie temperature and magnetic measurements. The as-milled samples were subsequently annealed in temperature range from 750 to 1050 {\deg}C for 30 min to optimize the extrinsic properties. From x-ray studies of magnetic aligned samples, the magnetic anisotropy of this compounds is found uniaxial. The Curie temperature is 349 {\deg}K and no saturation reached at room temperature for applied field of 90 kOe. The coercive field of 55 kOe and 12 kOe measured at 10 and 293 K respectively is obtained after annealing at 750 {\deg}C for 30 min suggests that nanocrystalline PrCo$_3$ are interesting candidates in the field of permanent magnets. We have completed this experimental study by simulations in the micromagnetic framework in order to get a qualitative picture of the microstructure effect on the macroscopic magnetization curve. From this simple model calculation, we can suggest that the after annealing the system behaves as magnetically hard crystallites embedded in a weakly magnetized amorphous matrix. PACS : 75.50.Bb, 75.50.Tt, 76.80.+y
Quantum algorithms speeding up classical counterparts are proposed for the problems:   1. Recognition of eigenvalues with fixed precision. Given a quantum circuit generating unitary mapping $U$ and a complex number the problem is to determine is it an eigenvalue of $U$ or not.   2. Given a molecular structure find thermodynamic functions like partitioning function, entropy, etc. for a gas consisting of such molecules.   3. Recognition of molecular structures. Find a molecular structure given its spectrum.   4. Recognition of electronic devices. Given an electronic device that can be used only as a black box how to recognize its internal construction?   We consider mainly structures generating sparse spectrums. These algorithms require the time from about square root to logarithm of the time of classical analogs and for the first three problems give exponential memory saving. Say, the time required for distinguishing two devices with the same given spectrum is about seventh root of the time of direct classical method, for the recognition of eigenvalue - about sixth root. Thus microscopic quantum devices can recognize molecular structures and physical properties of environment faster than big classical computers.
We complete an earlier derivation of the 4-point bosonic scattering amplitudes, and of the corresponding linearized local supersymmetric invariants in D=11 supergravity, by displaying the form-curvature, F^2 R^2, terms.
We have discovered new extended star clusters (ESCs) in a nearby dIrr galaxy NGC 6822. These clusters are the nearest sample of ESCs available to date. The key characteristic of ESCs is their large size compared to typical globular clusters even though the two cluster populations are rather similar in terms of other parameters, i.e., color and luminosity. Several scenarios have been suggested to explain the formation of ESCs. However, the currently known ESCs may be a mixture of populations with heterogeneous formation histories. Future observational and theoretical studies are expected to better constrain the origins of ESCs as well as to increase their sample size.
The density fluctuation spectrum $N({\bf k},\omega)$ is calculated for the t-J model in the low-doping regime using a slave-fermion method for the constrained fermions. The obtained results for $N({\bf k},\omega)$ are in good agreement with diagonalization results. The density response is characterized by incoherent, momentum dependent spectral functions reaching up to energies $\sim 8t$ and a low-energy structure at energy $\sim J$ due to transitions in the quasiparticle band. $N({\bf k},\omega)$ is shown to lead to a strong renormalization of planar bond-streching and breathing phonon modes with a large phonon linewidth at intermediate momenta caused by the low-energy response. Our results are consistent with recent neutron scattering data, showing the peculiar behavior of these modes.
The early--type galaxy (ETG) mass--size relation has been largely studied to understand how these galaxies have assembled their mass. One key observational result of the last years is that massive galaxies increased their size by a factor of a few at fixed stellar mass from $z\sim2$. Hierarchical models favor minor mergers as a plausible driver of this size growth. Some of these models, predict a significant environmental dependence in the sense that galaxies residing in more massive halos tend to be larger than galaxies in lower mass halos, at fixed stellar mass and redshift. At present, observational results of this environmental dependence have been contradictory. In this paper we revisit this issue in the local Universe, by investigating how the sizes of massive ETGs depend on large-scale environment using an updated and accurate sample of ETGs in different environments - field, group, clusters - from the Sloan Digital Sky Survey DR7. Our analysis does not show any significant environmental dependence of the sizes of central and satellites ETGs at fixed stellar mass at $z\sim0$. The size-mass relation of early-type galaxies at $z\sim0$ seems to be universal, i.e., independent of the mass of the host halo and of the position of the galaxy in that halo (central or satellite). The result is robust to different galaxy selections based on star formation, morphology or central density. In fact, considering our observational errors and the size of the sample, any size ratio larger than $30-40%$ between massive galaxies ($log(M_*/M_\odot)>11$) living in clusters and in the field can be ruled out at $3\sigma$ level.