ShantanuT01/DACTYL-Pretraining huggingface dataset:
X-ray polarimetry missions like IXPE will be able to measure for the first time the polarization properties of accreting, weakly magnetized neutron stars in Low Mass X-ray Binaries. In this work we present simulations of the expected X-ray polarized signal including the coronal emission for different geometries of the corona itself, i.e. a slab above the accretion disc and a spherical shell around the neutron star. The simulations are performed with the fully relativistic Monte Carlo code monk capable of computing the X-ray polarization degree and angle for various physical input parameters of the neutron star, disc and corona. Different coronal geometries result in significantly different X-ray polarization properties, which can therefore be used to constrain the geometry of the systems.
Despite the interest in dark matter and dark energy, it has never been shown that they are in fact two separate substances. We provide the first strong evidence that they are separate by ruling out a broad class of so-called unified dark matter models that have attracted much recent interest. We find that they produce oscillations or exponential blowup of the matter power spectrum inconsistent with observation. For the particular case of generalized Chaplygin gas models, 99.999% of the previously allowed parameter space is excluded, leaving essentially only the standard Lambda-CDM limit allowed.
The temporal evolution of the spectral break in the time resolved spectral energy density of the broad band afterglow of gamma ray bursts (GRBs) 091127 and 080319B was shown recently to be inconsistent with that expected for the cooling break in the standard fireball model of GRBs. Here we show that it is, however, in good agreement with the predicted temporal evolution of the smooth injection break/bend in the cannonball model of GRBs.
This is a survey of results about permanental processes, real valued positive processes which are a generalization of squares of Gaussian processes. In a certain sense the symmetric positive definite function that determines a Gaussian process is replaced by a function that is not necessarily symmetric nor positive definite, but that nevertheless determines a stochastic process. This is a new avenue of research with very many open problems.
We study a statistical mechanics model of a solid. Neighboring atoms are connected by Hookian springs. If the energy is larger than a threshold the "spring" is more likely to fail, while if the energy is lower than the threshold the spring is more likely to be alive. The phase diagram and thermodynamic quantities, such as free energy, numbers of bonds and clusters, and their fluctuations, are determined using renormalization-group and Monte-Carlo techniques.
We review our recent achievements in the construction of microscopic mass tables based on the Hartree-Fock-Bogoliubov method with Skyrme effective interactions. In the latest of our series of HFB-mass models, we have obtained our best fit ever to essentially all the available mass data, by treating the pairing more realistically than in any of our earlier models. The rms deviation on the 2149 measured masses of nuclei with N and Z>8 has been reduced for the first time in a mean field approach to 0.581 MeV. With the additional constraint on the neutron-matter equation of state, this new force is thus very well-suited for the study of neutron-rich nuclei and for the description of astrophysical environments like supernova cores and neutron-star crusts.
57Fe M\"{o}ssbauer spectroscopy was applied to an iron-based layered compound CeFePO. At temperatures from 9.4 to 293 K, no magnetic splitting was observed in the M\"ossbauer spectra of CeFePO indicating a paramagnetic phase of the Fe magnetic sublattice. All the spectra were fitted with a small quadrupole splitting, and the Debye temperature of CeFePO was found to be \sim448 K. The isomer shift at room temperature, 0.32 mm/s, was almost equal to those of LnFeAsO (Ln = La, Ce, Sm). Comparing s-electron density using the isomer shifts and unit cell volumes, it was found that the Fe of CeFePO has a similar valence state to other layered iron-based quaternary oxypnictides except LaFePO.
Clumpy structures are a common feature in X-ray images of young Type Ia supernova remnants (SNRs). Although the precise origin of such clumps remains unclear there are three generic possibilities: clumpiness imposed during the explosion, hydrodynamic instabilities that act during the remnant's evolution, and pre-existing structures in the ambient medium. In this article we focus on discriminating between clumping distributions that arise from the explosion and those from the remnant's evolution using existing 3D hydrodynamical simulations. We utilize the genus statistic for this discrimination, applying it to the simulations and {\it Chandra} X-ray observations of the well-known SN Ia remnant of SN 1572 (Tycho's SNR). The genus curve of Tycho's SNR strongly indicates a skewed non-Gaussian distribution of the ejecta clumps and is similar to the genus curve for the simulation with initially clumped ejecta. In contrast, the simulation of perfectly smooth ejecta where clumping arises from the action of hydrodynamic instabilities produced a genus curve that is similar to a random Gaussian field, but disagrees strongly with the genus curve of the observed image. Our results support a scenario in which the observed structure of SN Ia remnants arises from initial clumpiness in the explosion.
Gamma-ray bursts (GRBs) might be powered by a black hole (BH) hyperaccretion systems via the Blandford-Znajek (BZ) mechanism or neutrino annihilation from neutrino-dominated accretion flows (NDAFs). Magnetic coupling (MC) between the inner disc and BH can transfer angular momentum and energy from the fast-rotating BH to the disc. The neutrino luminosity and neutrino annihilation luminosity are both efficiently enhanced by the MC process. In this paper, we study the structure, luminosity, MeV neutrinos, and gravitational waves (GWs) of magnetized NDAFs (MNDAFs) under the assumption that both the BZ and MC mechanisms are present. The results indict that the BZ mechanism will compete with the neutrino annihilation luminosity to trigger jets under the different partitions of the two magnetic mechanisms. The typical neutrino luminosity and annihilation luminosity of MNDAFs are definitely higher than those of NDAFs. The typical peak energy of neutrino spectra of MNDAFs is higher than that of NDAFs, but similar to those of core-collapse supernovae. Moreover, if the MC process is dominant, then the GWs originating from the anisotropic neutrino emission will be stronger particularly for discs with high accretion rates.
The spectra obtained above 100 MeV by the EGRET experiment aboard the Compton Gamma-Ray Observatory for a handful of gamma-ray bursts has given no indication of any spectral attenuation that might preclude detection of bursts at higher energies. With the discovery of optical afterglows and counterparts to bursts in the last few years, enabling the determination of significant redshifts for these sources, it is anticipated that profound spectral attenuation will arise in the Gamma-Ray Large Area Space Telescope (GLAST) energy band of 30 MeV-300 GeV for many if not most bursts. This paper explores time-dependent expectations for burst spectral properties in the EGRET/GLAST band, focusing on how attenuation of photons by pair creation internal to the source generates distinctive spectral signatures. The energy of spectral breaks and the associated spectral indices provide valuable information that constrains the bulk Lorentz factor of the GRB outflow at a given time. Moreover, the distinct temporal behavior that is present for internal attenuation is easily distinguished from extrinsic absorption due to intervening cosmic background fields. These characteristics define palpable observational goals for both spaced-based hard gamma-ray experiments such as GLAST, and ground-based Cherenkov telescopes, and strongly impact the observability of bursts above 300 MeV.
We give an explicit construction of the increasing tree-valued process introduced by Abraham and Delmas using a random point process of trees and a grafting procedure. This random point process will be used in companion papers to study record processes on L\'evy trees. We use the Poissonian structure of the jumps of the increasing tree-valued process to describe its behavior at the first time the tree grows higher than a given height. We also give the joint distribution of this exit time and the ascension time which corresponds to the first infinite jump of the tree-valued process.
Advances in computing have enabled widespread access to pose estimation, creating new sources of data streams. Unlike mock set-ups for data collection, tapping into these data streams through on-device active learning allows us to directly sample from the real world to improve the spread of the training distribution. However, on-device computing power is limited, implying that any candidate active learning algorithm should have a low compute footprint while also being reliable. Although multiple algorithms cater to pose estimation, they either use extensive compute to power state-of-the-art results or are not competitive in low-resource settings. We address this limitation with VL4Pose (Visual Likelihood For Pose Estimation), a first principles approach for active learning through out-of-distribution detection. We begin with a simple premise: pose estimators often predict incoherent poses for out-of-distribution samples. Hence, can we identify a distribution of poses the model has been trained on, to identify incoherent poses the model is unsure of? Our solution involves modelling the pose through a simple parametric Bayesian network trained via maximum likelihood estimation. Therefore, poses incurring a low likelihood within our framework are out-of-distribution samples making them suitable candidates for annotation. We also observe two useful side-outcomes: VL4Pose in-principle yields better uncertainty estimates by unifying joint and pose level ambiguity, as well as the unintentional but welcome ability of VL4Pose to perform pose refinement in limited scenarios. We perform qualitative and quantitative experiments on three datasets: MPII, LSP and ICVL, spanning human and hand pose estimation. Finally, we note that VL4Pose is simple, computationally inexpensive and competitive, making it suitable for challenging tasks such as on-device active learning.
We propose the implementation of a strongly-driven one-atom laser, based on the off-resonant interaction of a three-level atom in $\Lambda$-configuration with a single cavity mode and three laser fields. We show that the system can be described equivalently by a two-level atom resonantly coupled to the cavity and driven by a strong effective coherent field. The effective dynamics can be solved exactly, including a thermal field bath, allowing an analytical description of field statistics and entanglement properties. We also show the possible generation of Schr\"odinger cat states for the whole atom-field system and for the field alone after atomic measurement. We propose a way to monitor the system decoherence by measuring atomic population. Finally, we confirm the validity of our model through numerical solutions.
Scattering, during interplanetary transport in large, "gradual" solar energetic-particle (SEP) events, can cause element abundance enhancements or suppressions that depend upon the mass-to-charge ratio A/Q of the ions as an increasing function early in events and a decreasing function of the residual scattered ions later. Since the Q values for the ions depend upon the source plasma temperature T, best fits, assuming a primarily power-law dependence of enhancements vs. A/Q, provide a fundamentally new method to determine the most probable value of T for these events in the region of 3-10 MeV/amu. Complicated variations in the grouping of element enhancements or suppressions match similar variations in A/Q at the best-fit temperature. We find that fits to the times of increasing and decreasing powers give similar values of T, most commonly in the range of 0.8-1.6 MK for 69% of the events, consistent with the acceleration of ambient coronal plasma by shock waves driven out from the Sun by coronal mass ejections (CMEs). However, 24% of the SEP events studied showed plasma of 2.5-3.2 MK, typical of that previously determined for the smaller impulsive SEP events; these particles may be reaccelerated preferentially by quasi-perpendicular shock waves that require a high injection threshold that the impulsive-event ions exceed or simply by high intensities of impulsive suprathermal ions at the shock. The source-temperature distribution of ten higher-energy ground-level events (GLEs) in the sample is similar to that of the other gradual events. Some events show evidence that a portion of the ions have been further stripped of electrons; such events are smaller and tend to cluster late in the solar cycle.
Silicon heterojunction (SHJ) solar cells with an interdigitated back-contact (IBC) exhibit high conversion efficiencies of up to 25.6%. However, due to the sophisticated back-side pattern of the doped layers and electrode structure many processing and patterning steps are required. A simplification of the patterning steps could ideally increase the yield and/or lower the production costs. We propose a patterning approach for IBC SHJ solar cells free of any photo-lithography with the help of laser-induced forward transfer (LIFT) of the individual layer stacks to create the required back-contact pattern. The concept has the potential to lower the number of processing steps significantly while at the same time giving a large degree of freedom in the processing conditions optimization of emitter and BSF since deposition of the intrinsic/doped layers and processing of the wafer are all independent from each other.
As a transient X-ray binary, MAXI J1659-152 contains a black hole candidate as its compact star. MAXI J1659-152 was discovered on 2010 September 25 during its only known outburst. Previously-published studies of this outburst indicate that MAXI J1659-152 may have an extreme retrograde spin, which, if confirmed, would provide an important clue as to the origin of black hole spin. In this paper, utilizing updated dynamical binary-system parameters (i.e. the black hole mass, the orbital inclination and the source distance) provided by \cite{Torres2021}, we analyze 65 spectra of MAXI J1659-152 from \emph{RXTE}/PCA, in order to assess the spin parameter. With a final selection of 9 spectra matching our $f_{\mathrm{sc}} \lesssim 25 \%$, soft-state criteria, we apply a relativistic thin disk spectroscopic model \texttt{kerrbb2} over 3.0-45.0 keV. We find that inclination angle correlates inversely with spin, and, considering the possible values for inclination angle, we constrain spin to be $-1 < a_{*} \lesssim 0.44$ at 90\% confidence interval via X-ray continuum-fitting. We can only rule out an extreme prograde (positive) spin. We confirm that an extreme retrograde solution is possible and is not ruled out by considering accretion torques given the young age of the system.
The LambdaCDM model of cosmology, though very successful at large scales, has some discrepancy with observations at the galactic and sub-galactic scales. These include the core-cusp problem, missing satellites problem etc. Spergel and Steingardt (2000) proposed that if dark matter undergoes feeble self interactions with each other, then such problems can be averted. In this thesis, a two-component Feebly Interacting Massive Particle (FIMP) dark matter model involving two singlet scalar fields capable of self-interactions has been proposed and its impact on large scale structure formation has been studied through cosmological simulations. The proposed model involves simple extensions of the Standard Model with two singlet scalar fields formed non-thermally through the decay of heavier particles in the very early universe. These particles acquire their relic abundance through a freeze-in mechanism. The coupled Boltzmann equation of the FIMP-FIMP model was solved and the relic densities for different values of the coupling parameters were obtained and matched with PLANCK results. The impact of dark matter self interactions was studied through cosmological simulations using a modified version of the parallel TreePM code GADGET-2 and the halo mass function and halo catalog for different dark matter self interaction cross sections were obtained. Lastly, the newly developed Effective Theory of Structure Formation (ETHOS) framework which is a new and innovative paradigm in the study of the cosmological effects of different dark matter models was studied and using the public code, ETHOS-CAMB the signatures of dark acoustic oscillations in the matter power spectrum for a particular dark matter model was obtained.
For fixed integers $r>k\ge 2,e\ge 3$, let $f_r(n,er-(e-1)k,e)$ be the maximum number of edges in an $r$-uniform hypergraph in which the union of any $e$ distinct edges contains at least $er-(e-1)k+1$ vertices. A classical result of Brown, Erd\H{o}s and S\'os in 1973 showed that $f_r(n,er-(e-1)k,e)=\Theta(n^k).$ The degenerate Tur\'an density is defined to be the limit (if it exists) $$\pi(r,k,e):=\lim_{n\rightarrow\infty}\frac{f_r(n,er-(e-1)k,e)}{n^k}.$$ Extending a recent result of Glock for the special case of $r=3,k=2,e=3$, we show that $$\pi(r,2,3):=\lim_{n\rightarrow\infty}\frac{f_r(n,3r-4,3)}{n^2}=\frac{1}{r^2-r-1}$$ for arbitrary fixed $r\ge 4$. For the more general cases $r>k\ge 3$, we show that $$\frac{1}{r^k-r}\le\liminf_{n\rightarrow\infty}\frac{f_r(n,3r-2k,3)}{n^k}\le\limsup_{n\rightarrow\infty}\frac{f_r(n,3r-2k,3)}{n^k}\le \frac{1}{k!\binom{r}{k}-\frac{k!}{2}}.$$   The main difficulties in proving these results are the constructions establishing the lower bounds. The first construction is recursive and purely combinatorial, and is based on a (carefully designed) approximate induced decomposition of the complete graph, whereas the second construction is algebraic, and is proved by a newly defined matrix property which we call {\it strongly 3-perfect hashing}.
The energies and decay widths of the states of the exotic 7He nucleus are studied in an ab initio approach. The spectrum of these states is calculated using No-Core Shell Model and corresponding extrapolation procedure. Well-proven on a large amount of data the Daejeon16 potential is used in the calculations. The previously developed NCSM-based approach, which includes a method for constructing the basis of orthogonalized functions of cluster channels and a procedure for matching the cluster form factors obtained within this method with the corresponding asymptotic wave functions, is applied to compute the decay widths of the levels. The possibilities of the approach for calculating the partial decay widths of nuclear states into various channels strongly differing in type of fragmentation, spin, angular momentum of relative motion, and amplitude are demonstrated. The results obtained are compared with the results of other microscopic calculations.
One of the most common tasks in medical imaging is semantic segmentation. Achieving this segmentation automatically has been an active area of research, but the task has been proven very challenging due to the large variation of anatomy across different patients. However, recent advances in deep learning have made it possible to significantly improve the performance of image recognition and semantic segmentation methods in the field of computer vision. Due to the data driven approaches of hierarchical feature learning in deep learning frameworks, these advances can be translated to medical images without much difficulty. Several variations of deep convolutional neural networks have been successfully applied to medical images. Especially fully convolutional architectures have been proven efficient for segmentation of 3D medical images. In this article, we describe how to build a 3D fully convolutional network (FCN) that can process 3D images in order to produce automatic semantic segmentations. The model is trained and evaluated on a clinical computed tomography (CT) dataset and shows state-of-the-art performance in multi-organ segmentation.
This paper is devoted to the adaptation of the method developed in [4,3] to a Fokker-Planck equation for fiber lay-down which has been studied in [1,5]. Exponential convergence towards a unique stationary state is proved in a norm which is equivalent to a weighted $L^2$ norm. The method is based on a micro / macro decomposition which is well adapted to the diffusion limit regime.
We introduce a new technique to bound the fluctuations exhibited by a physical system, based on the Euclidean geometry of the space of observables. Through a simple unifying argument, we derive a sweeping generalization of so-called Thermodynamic Uncertainty Relations (TURs). We not only strengthen the bounds but extend their realm of applicability and in many cases prove their optimality, without resorting to large deviation theory or information-theoretic techniques. In particular, we find the best TUR based on entropy production alone and also derive a novel bound for stationary Markov processes, which surpasses previous known bounds. Our results derive from the non-invariance of the system under a symmetry which can be other than time reversal and thus open a wide new spectrum of applications.
We present a scheme of interaction-induced topological bandstructures based on the spin anisotropy of exciton-polaritons in semiconductor microcavities. We predict theoretically that this scheme allows the engineering of topological gaps, without requiring a magnetic field or strong spin-orbit interaction (transverse electric-transverse magnetic splitting). Under non-resonant pumping, we find that an initially topologically trivial system undergoes a topological transition upon the spontaneous breaking of phase symmetry associated with polariton condensation. Under resonant coherent pumping, we find that it is also possible to engineer a topological dispersion that is linear in wavevector -- a property associated with polariton superfluidity.
We propose two systems of "intrinsic" signs for counting such curves. In both cases the result acquires an exceptionally strong invariance property: it does not depend on the choice of a surface. One of our counts includes all divisor classes of canonical degree 2 and gives in total 30. The other one excludes the class $-2K$, but adds up the results of counting for a pair of real structures that differ by Bertini involution. This count gives 96.
DM--DE coupling can be a phenomenological indication of a common origin of the dark cosmic components. In this work we outline a new constraint to coupled--DE models: the coupling can partially or totally suppress the Meszaros effect, yielding transfered spectra with quite a soft bending above $k_{hor,eq}$. Models affected by this anomaly do not show major variation in the CMB anisotropy spectrum and it is herefore hard to reconcile them with both CMB and deep sample data, through the same value of the primeval spectral index.