ShantanuT01/DACTYL-Pretraining huggingface dataset:
Usual explanations of spiral galaxy rotation curves assume circular orbits of stars. The consequences of giving up this assumption are investigated here. In particular, hyperbolic stellar trajectories are found to be interesting. The two suggested models for the production of such trajectories will also explain the observed flat rotation curves without the postulation of dark matter or MOND. It is suggested that spiral galaxies may have started as compact objects with significant angular momenta and then disintegrated. The first model conjectures the existence of a spinning hot disk around a spherical galactic core. The disk is held together by local gravity and electromagnetic scattering forces. However, it disintegrates at the edge producing fragments that form stars. Once separated from the disk, the stars experience only the centrally directed gravitational force due to the massive core and remaining disk. A numerical simulation shows that a high enough angular velocity of the disk produces hyperbolic stellar trajectories that agree with the observed rotation curves. The second model conjectures a significant initial thermonuclear event that produces a dust plume along with large stars. This dust plume is made of ordinary matter. However, it acts like the postulated dark matter in producing initial circular trajectories. Unlike dark matter, the plume can be shown to escape the galaxy rapidly causing the star trajectories to evolve to hyperbolic shapes. This process can be seen to produce the observed rotation curves due to the initial circular orbits. Also, as the plume dissipates rapidly it does not obfuscate the stars from view. Both models have weaknesses as do the currently known models using dark matter or MOND.
We control transition frequency of a superconducting flux qubit coupled to a frequency-tunable resonator comprising a direct current superconducting quantum interference device (dc-SQUID) by microwave driving. The dc-SQUID mediates the coupling between microwave photons in the resonator and a flux qubit. The polarity of the frequency shift depends on the sign of the flux bias for the qubit and can be both positive and negative. The absolute value of the frequency shift becomes larger by increasing the photon number in the resonator. These behaviors are reproduced by a model considering the magnetic interaction between the flux qubit and dc-SQUID. The tuning range of the transition frequency of the flux qubit reaches $\approx$ 1.9 GHz, which is much larger than the ac Stark/Lamb shift observed in the dispersive regime using typical circuit quantum electrodynamics devices.
Although having achieved great success in medical image segmentation, deep convolutional neural networks usually require a large dataset with manual annotations for training and are difficult to generalize to unseen classes. Few-shot learning has the potential to address these challenges by learning new classes from only a few labeled examples. In this work, we propose a new framework for few-shot medical image segmentation based on prototypical networks. Our innovation lies in the design of two key modules: 1) a context relation encoder (CRE) that uses correlation to capture local relation features between foreground and background regions; and 2) a recurrent mask refinement module that repeatedly uses the CRE and a prototypical network to recapture the change of context relationship and refine the segmentation mask iteratively. Experiments on two abdomen CT datasets and an abdomen MRI dataset show the proposed method obtains substantial improvement over the state-of-the-art methods by an average of 16.32%, 8.45% and 6.24% in terms of DSC, respectively. Code is publicly available.
Using published HST Cepheid data from 25 galaxies, we have found a correlation between the P-L dispersion and host galaxy metallicity which is significant at the ~3sigma level in the V band. This result supports the suggestion that the metallicity dependence of the Cepheid P-L relation may be stronger than expected. The high observed dispersions in the HST Cepheid P-L relations have the further consequence that the bias due to incompleteness in the P-L relation at faint magnitudes is more significant than previously thought. In the HST sample, galaxies at higher distance tend to have higher metallicity. This means that when a full metallicity/incompleteness correction is made, a scale error in the published Cepheid distances is seen in the sense that the published distance moduli are increasingly underestimates at larger distances. This results in the average distance modulus to the four galaxies in the Virgo cluster core increasing from (m-M)_0=31.2+-0.19 to (m-M)_0=31.8+-0.17 with similar increases for the Fornax and Ursa Major clusters. For the 18 HST galaxies with good Tully-Fisher distances and (m-M)_0>29.5 the Cepheid-TF distance modulus average residual increases from 0.44+-0.09 mag to 0.82+-0.1mag indicating a significant scale error in TF distances and resulting in the previous Pierce & Tully TF estimate of H_0=85 reducing to H_0=58+-7. Finally, for the 8 HST galaxies with SNIa, the metallicity corrected Cepheid distances now imply a metallicity dependence of SNIa peak luminosity in the sense that metal-poor hosts have lower luminosity SNIa. Thus SNIa Hubble diagram estimates of both H_0 and q_0 may also require significant metallicity corrections.
We propose a mechanism for the spontaneous (gauge-invariant) reduction of noncommutative ${\cal U}(n)$ gauge theories down to SU(n). This can be achieved through the condensation of composite ${\cal U}(n)$ gauge invariant fields that involves half-infinite Wilson lines in trace-U(1) noninvariant and SU(n) preserving direction. Based on this mechanism we discuss anomaly-free fully gauge invariant noncommutative Standard Model based on the minimal gauge group ${\cal U}(3)\times {\cal U}(2)\times {\cal U}(1)$, previously proposed, and show how it can be consistently reduced to the Standard Model with the usual particle spectrum. Charge quantization for quarks and leptons naturally follows from the model.
The most luminous X-ray sources in nearby elliptical galaxies are likely black hole low-mass X-ray binaries (BHLMXBs). In the Milky Way, such systems are always transient, and with the exception of GRS1915+105 have burst durations on the order of weeks or months. However, the low duty cycle of short-duration outburst BHLMXBs makes it improbable that any one source would be caught in an outburst during a single snapshot observation. Long-duration outburst BHLMXBs, although much rarer, would be detectable in a series of snapshot observations separated by several years. Our analysis of multi-epoch Chandra observations of the giant elliptical galaxies NGC1399 and M87 separated by 3.3 and 5.3 yr, respectively, finds that all 37 luminous (>8 x 10^38 ergs/s) X-ray sources that were present in the first epoch observations were still in outburst in all of the following observations. Many of these probable long-duration outburst BHLMXBs reside within globular clusters of the galaxies. Conversely, no definitive short-duration outburst BHLMXBs were detected in any of the observations. This places an upper limit on the ratio of short--to--long-duration outbursters that is slightly lower, but consistent with what is seen in the Milky Way. The fact that none of the luminous sources turned off between the first and last epochs places a 95 per cent lower limit of 50 yr on the mean burst duration of the long-duration outburst sources. The most likely scenario for the origin of these sources is that they are long-period (>30 d) black hole binaries with a red giant donor, much like GRS1915+105. However, unlike GRS1915+105, most of the sources show only modest variability from epoch to epoch.
The goal of this thesis is to present my research contributions towards solving various visual synthesis and generation tasks, comprising image translation, image completion, and completed scene decomposition. This thesis consists of five pieces of work, each of which presents a new learning-based approach for synthesizing images with plausible content as well as visually realistic appearance. Each work demonstrates the superiority of the proposed approach on image synthesis, with some further contributing to other tasks, such as depth estimation.
We study the largest particle-number-preserving sector of the dilatation operator in maximally supersymmetric gauge theory. After exploring one-loop Bethe Ansatze for the underlying spin chain with psl(2|2) symmetry for simple root systems related to several Kac-Dynkin diagrams, we use the analytic Bethe Anzats to construct eigenvalues of transfer matrices with finite-dimensional atypical representations in the auxiliary space. We derive closed Baxter equations for eigenvalues of nested Baxter operators. We extend these considerations for a non-distinguished root system with FBBF grading to all orders of perturbation theory in 't Hooft coupling. We construct generating functions for all transfer matrices with auxiliary space determined by Young supertableaux (1^a) and (s) and find determinant formulas for transfer matrices with auxiliary spaces corresponding to skew Young supertableaux. The latter yields fusion relations for transfer matrices with auxiliary space corresponding to representations labelled by square Young supertableaux. We derive asymptotic Baxter equations which determine spectra of anomalous dimensions of composite Wilson operators in noncompact psl(2|2) subsector of N=4 super-Yang-Mills theory.
No mechanisms have hitherto been conclusively demonstrated to be responsible for initiating optically-luminous nuclear (Seyfert) activity in local disk galaxies. Only a small minority of such galaxies are visibly disturbed in optical starlight, with the observed disturbances being at best marginally stronger than those found in matched samples of inactive galaxies. Here, we report the first systematic study of an optically-selected sample of twenty-three active galaxies in atomic hydrogen (HI) gas, which is the most sensitive and enduring tracer known of tidal interactions. Eighteen of these galaxies are (generally) classified as Seyferts, with over half (and perhaps all) having [OIII] luminosities within two orders of magnitude of Quasi-Stellar Objects. Only ~28% of these Seyfert galaxies are visibly disturbed in optical DSS2 images. By contrast, ~94% of the same galaxies are disturbed in HI, in nearly all cases not just spatially but also kinematically on galactic (>~20 kpc) scales. In at least ~67% and perhaps up to ~94% of cases, the observed HI disturbances can be traced to tidal interactions with neighboring galaxies detected also in HI. The majority of these neighboring galaxies have projected separations of <~ 100 kpc and differ in radial velocities by <~100 km/s from their respective Seyfert galaxies, and many have optical luminosities ranging from the Small to Large Magellanic Clouds. In a companion paper, we show that only ~15% of a matched control sample of inactive galaxies display comparable HI disturbances. Our results suggest that: i) most Seyfert galaxies (with high nuclear luminosities) have experienced tidal interactions in the recent past; ii) in most cases, these tidal interactions are responsible for initiating events that lead to their nuclear activity.
Two body non-leptonic decays:Lambda_b-->Lambda_c P(V) are investigated. Baryon form factors of the heavy quark effective theory are employed. Form factors for renormalization in full QCD are also considered. We find that contributions of the non-factorizable terms are negligible in b-decays. Comparison with calculations in other models shows that form factors for renormalization in full QCD should be more relevant. The asymmetry parameters are negative as in the charmed baryons cases. An experimental measure on the form factors V1 and A1 is accentuated to test the validity of HQET.
A theoretical light curve for the 1999 outburst of U Scorpii is presented in order to obtain various physical parameters of the recurrent nova. Our U Sco model consists of a very massive white dwarf (WD) with an accretion disk and a lobe-filling, slightly evolved, main-sequence star (MS). The model includes a reflection effect by the companion and the accretion disk together with a shadowing effect on the companion by the accretion disk. The early visual light curve (t ~ 1-15 days after maximum) is well reproduced by a thermonuclear runaway model on a very massive WD close to the Chandrasekhar limit (M_{WD}= 1.37 \pm 0.01 M_\odot), in which optically thick winds blowing from the WD play a key role in determining the nova duration. The duration of the strong wind phase (t~0-17 days) is very consistent with the BeppoSAX supersoft X-ray detection at t~19-20 days because supersoft X-rays are self-absorbed by the massive wind. The envelope mass at the peak is estimated to be ~3x10^{-6} M_\odot, which is indicating an average mass accretion rate ~2.5x10^{-7} M_\odot yr^{-1} during the quiescent phase between 1987 and 1999. These quantities are exactly the same as those predicted in a new progenitor model of Type Ia supernovae.
We report on the torus constraints of the Compton-thick AGN with double-peaked optical narrow line region (NLR) emission lines, ANEPD-CXO245, at z=0.449 in the AKARI NEP Deep Field. The unique infrared data on this field, including those from the nine-band photometry over 2-24 $\mu$m with the AKARI Infrared Camera (IRC), and the X-ray spectrum from Chandra allow us to constrain torus parameters such as the torus optical depth, X-ray absorbing column, torus angular width ($\sigma$) and viewing angle ($i$). We analyze the X-ray spectrum as well as the UV-optical-infrared spectral energy distribution (UOI-SED) with clumpy torus models in X-ray (XCLUMPY; Tanimoto et al. 2019) and infrared (CLUMPY; Nenkova et al. 2008) respectively. From our current data, the constraints on $\sigma$--$i$ from both X-rays and UOI show that the line of sight crosses the torus as expected for a type 2 AGN. We obtain a small X-ray scattering fraction (<0.1%), which suggests narrow torus openings, giving preference to the bi-polar outflow picture of the double-peaked profile. Comparing the optical depth of the torus from the UOI-SED and the absorbing column density $N_{\rm H}$ from the X-ray spectrum, we find that the gas-to-dust ratio is $\gtrsim 4$ times larger than the Galactic value.
Let $(W,H,\mu)$ be an abstract Wiener space and $L$ be a probability density of class LlogL. Using the measure transportation of Monge-Kantorovitch, we prove that the kernel of the projection of L on the second Wiener chaos defines an (Hilbert-Schmidt) operator which is lower bounded by another Hilbert-Schmidt operator.
We have measured the heat conduction between 0.05 K and 1.0 K of high purity silicon wafers carrying on their polished faces a variety of thin dielectric films and polycrystalline thin metallic films. Using a Monte Carlo simulation to analyze the conduction measurements, we have determined the phonon mean free path within the films, and found all of them to be much shorter even than in typical bulk amorphous solids, with no exceptions. We have also measured the internal friction of these films below 10 K and found, however, their internal friction at low temperatures strikingly close to that of amorphous solids, both in magnitude and in their temperature independence, with the exception of the MBE Si and alloy Al 5056, whose internal friction is even much smaller than that of amorphous solids. The internal friction results indicate the phonon scattering in these thin films is the same as, or even much less stronger than, in other amorphous solids, according to the Tunneling Model. Thus, we conclude that the heat conduction measurements do not support the picture that the lattice vibrations of these films are glasslike, as had been surmised earlier for thin metallic films, on the basis of low temperature internal friction measurements alone [Phys. Rev. B 59, 11767 (1999)]. At the least, the films must contain additional scattering centers which lead to the very small phonon mean free path. Most remarkably, the MBE Si shows the same strong scattering of thermal phonons as do the other films, while having the negligible internal friction expected for a perfect film. The disorder causing the strong scattering of the thermal phonons in this film is completely unknown. The non-glasslike phonon scattering phenomena observed here in thin dielectric and metallic films deserve further investigations.
A literature survey of experimentally measured mobility values for the two-dimensional materials MoS2, MoSe2, MoTe2, WS2, WSe2, and black phosphorous carried out during 2015.
Self-assembled functionalized nano particles are at the focus of a number of potential applications, in particular for molecular scale electronics devices. Here we perform experiments of self-assembly of 10 nm Au nano particles (NPs), functionalized by a dense layer of azobenzene-bithiophene (AzBT) molecules, with the aim of building a light-switchable device with memristive properties. We fabricate planar nanodevices consisting of NP self-assembled network (NPSANs) contacted by nanoelectrodes separated by interelectrode gaps ranging from 30 to 100 nm. We demonstrate the light-induced reversible switching of the electrical conductance in these AzBT NPSANs with a record on/off conductance ratio up to 620, an average value of ca. 30 and with 85% of the devices having a ratio above 10. Molecular dynamics simulation of the structure and dynamics of the interface between molecular monolayers chemisorbed on the nano particle surface are performed and compared to the experimental findings. The properties of the contact interface are shown to be strongly correlated to the molecular conformation which in the case of AzBT molecules, can reversibly switched between a cis and a trans form by means of light irradiations of well-defined wavelength. Molecular dynamics simulations provide a microscopic explanation for the experimental observation of the reduction of the on/off current ratio between the two isomers, compared to experiments performed on flat self-assembled monolayers contacted by a conducting cAFM tip.
The calculation of line widths constitutes theoretical and computational challenges in the calculation of opacities of hot dense plasmas. Opacity models use line broadening approximations that are untested at stellar interior conditions. Moreover, calculations of atomic spectra of the sun, indicate a large discrepancy in the K-shell line widths between several atomic codes and the OP. In this work, the atomic code STAR is used to study the sensitivity of solar opacities to line-broadening. Variations in the solar opacity profile, due to an increase of the Stark widths resulting from discrepancies with OP, are compared, in light of the solar opacity problem, with the required opacity variations of the present day sun, as imposed by helioseismic and neutrino observations. The resulting variation profile, is much larger than the discrepancy between different atomic codes, agrees qualitatively with the missing opacity profile, recovers about half of the missing opacity nearby the convection boundary and has a little effect in the internal regions. Since it is hard to estimate quantitatively the uncertainty in the Stark widths, we show that an increase of all line widths by a factor of about 100 recovers quantitatively the missing opacity. These results emphasize the possibility that photoexcitation processes are not modeled properly, and more specifically, highlight the need for a better theoretical characterization of the line broadening phenomena at stellar interior conditions and of the uncertainty due to the way it is implemented by atomic codes.
Given a non-rational real space curve and a tolerance $\epsilon>0$, we present an algorithm to approximately parametrize the curve. The algorithm checks whether a planar projection of the space curve is $\epsilon$-rational and, in the affirmative case, generates a planar parametrization that is lifted to an space parametrization. This output rational space curve is of the same degree as the input curve, both have the same structure at infinity, and the Hausdorff distance between them is always finite.
The recent advancements in deep learning have allowed for numerous applications in computed tomography (CT), with potential to improve diagnostic accuracy, speed of interpretation, and clinical efficiency. However, the deep learning community has to date neglected window display settings - a key feature of clinical CT interpretation and opportunity for additional optimization. Here we propose a window setting optimization (WSO) module that is fully trainable with convolutional neural networks (CNNs) to find optimal window settings for clinical performance. Our approach was inspired by the method commonly used by practicing radiologists to interpret CT images by adjusting window settings to increase the visualization of certain pathologies. Our approach provides optimal window ranges to enhance the conspicuity of abnormalities, and was used to enable performance enhancement for intracranial hemorrhage and urinary stone detection. On each task, the WSO model outperformed models trained over the full range of Hounsfield unit values in CT images, as well as images windowed with pre-defined settings. The WSO module can be readily applied to any analysis of CT images, and can be further generalized to tasks on other medical imaging modalities.
The transverse nucleon spin can be transferred to the quarks and gluons in several ways. In the factorizing, hard scattering processes to be considered, these are parameterized at leading twist by the transversity distribution function and at next-to-leading twist by quark-gluon correlation functions. The latter enter the description of the structure function $g_2$ and possibly of single spin asymmetries. It is discussed what is known about these functions and what are the remaining open issues.
We report a surprisingly long spin relaxation time of electrons in Mn-doped p-GaAs. The spin relaxation time scales with the optical pumping and increases from 12 ns in the dark to 160 ns upon saturation. This behavior is associated with the difference in spin relaxation rates of electrons precessing in the fluctuating fields of ionized or neutral Mn acceptors, respectively. For the latter the antiferromagnetic exchange interaction between a Mn ion and a bound hole results in a partial compensation of these fluctuating fields, leading to the enhanced spin memory.
Einstein-Smoluchowski diffusion, damped harmonic oscillations, and spatial decoherence are special cases of an elegant class of Markovian quantum Brownian motion models that is invariant under linear symplectic transformations. Here we prove that for each member of this class there is a preferred timescale such that the dynamics, considered stroboscopically, can be rewritten exactly as unitary evolution interrupted periodically by an entanglement-breaking measurement with respect to a fixed overcomplete set of pure Gaussian states. This is relevant to the continuing search for the best way to describe pointer states and pure decoherence in systems with continuous variables, and gives a concrete sense in which the decoherence can be said to arise from a complete measurement of the system by its environment. We also extend some of the results of Di\'{o}si and Kiefer to the symplectic covariant formalism and compare them with the preferred timescales and Gaussian states associated with the POVM form.