ShantanuT01/DACTYL-Pretraining huggingface dataset:
We revisit the idea that density-wave wakes of planets drive accretion in protostellar disks. The effects of many small planets can be represented as a viscosity if the wakes damp locally, but the viscosity is proportional to the damping length. Damping occurs mainly by shocks even for earth-mass planets. The excitation of the wake follows from standard linear theory including the torque cutoff. We use this as input to an approximate but quantitative nonlinear theory based on Burger's equation for the subsequent propagation and shock. Shock damping is indeed local but weakly so. If all metals in a minimum-mass solar nebula are invested in planets of a few earth masses each, dimensionless viscosities [alpha] of order dex(-4) to dex(-3) result. We compare this with observational constraints. Such small planets would have escaped detection in radial-velocity surveys and could be ubiquitous. If so, then the similarity of the observed lifetime of T Tauri disks to the theoretical timescale for assembling a rocky planet may be fate rather than coincidence.
We present Keck Interferometer observations of T Tauri and Herbig Ae/Be stars with a spatial resolution of a few milliarcseconds and a spectral resolution of ~2000. Our observations span the K-band, and include the Br gamma transition of Hydrogen and the v=2-0 and v=3-1 transitions of carbon monoxide. For several targets we also present data from Keck/NIRSPEC that provide higher spectral resolution, but a seeing-limited spatial resolution, of the same spectral features. We analyze the Br gamma emission in the context of both disk and infall/outflow models, and conclude that the Br gamma emission traces gas at very small stellocentric radii, consistent with the magnetospheric scale. However some Br gamma-emitting gas also seems to be located at radii of >0.1 AU, perhaps tracing the inner regions of magnetically launched outflows. CO emission is detected from several objects, and we generate disk models that reproduce both the KI and NIRSPEC data well. We infer the CO spatial distribution to be coincident with the distribution of continuum emission in most cases. Furthermore the Br gamma emission in these objects is roughly coincident with both the CO and continuum emission. We present potential explanations for the spatial coincidence of continuum, Br gamma, and CO overtone emission, and explore the implications for the low occurrence rate of CO overtone emission in young stars. Finally, we provide additional discussion of V1685 Cyg, which is unusual among our sample in showing large differences in emitting region size and spatial position as a function of wavelength.
Insulated cantilever probes with a high aspect ratio conducting apex have been fabricated and their dynamic and electrical properties analyzed. The cantilevers were coated with silicon dioxide and a via was fabricated through the oxide at the tip apex and backfilled with tungsten to create an insulated probe with a conducting tip. The stiffness and Q-factor of the cantilevers increased after the modifications and their resonances shifted to higher frequencies. The coupling strength between the cantilever and the coating are determined. The applications to conductive and electromechanical imaging of ferroelectric domains are illustrated, and a probe apex repair process is demonstrated.
A singularly perturbed phase field model used to model lithium-ion batteries including chemical and elastic effects is considered. The underlying energy is given by $$I_\epsilon [u,c ] := \int_\Omega \left( \frac{1}{\epsilon} f(c) + \epsilon\|\nabla c\|^2 + \frac{1}{\epsilon}\mathbb{C} (e(u)-ce_0) : (e(u)-ce_0)\right) dx, $$ where $f$ is a double well potential, $\mathbb{C}$ is a symmetric positive definite fourth order tensor, $c$ is the normalized lithium-ion density, and $u$ is the material displacement. The integrand contains elements close to those in energy functionals arising in both the theory of fluid-fluid and solid-solid phase transitions. For a strictly star-shaped, Lipschitz domain $\Omega \subset \mathbb{R}^2,$ it is proven that $\Gamma - \lim_{\epsilon\to 0} I_\epsilon = I_0,$ where $I_0$ is finite only for pairs $(u,c)$ such that $f(c) = 0$ and the symmetrized gradient $e(u) = ce_0$ almost everywhere. Furthermore, $I_0$ is characterized as the integral of an anisotropic interfacial energy density over sharp interfaces given by the jumpset of $c.$
The Wilkinson Microwave Anisotropy Probe (WMAP) experiment has detected reionization at the $5.5 \sigma$ level and has reported a mean optical depth of $0.088 \pm 0.015$. A powerful probe of reionization is the large-angle $EE$ polarization power spectrum, which is now (since the first five years of data from WMAP) cosmic variance limited for $2\le l \le6$. Here we consider partial reionization caused by WIMP dark matter annihilation, and calculate the expected polarization power spectrum. We compare the dark matter models with a standard 2-step reionization theory, and examine whether the models may be distinguished using current, and future CMB observations. We consider dark matter annihilation at intermediate redshifts ($z<60$) due to halos, as well as annihilation at higher redshifts due to free particles. In order to study the effect of high redshift dark matter annihilation on CMB power spectra, it is essential to include the contribution of residual electrons (left over from recombination) to the ionization history. Dark matter halos at redshifts $z<60$ influence the low multipoles $l<20$ in the $EE$ power spectrum, while the annihilation of free particle dark matter at high redshifts $z>100$ mainly affects multipoles $l>10$.
F. Campana had asked whether a certain threefold is rational. In arXiv:1310.3569v1 [mathAG], this variety was shown to be birational to a specific conic bundle and then to be unirational. We prove that this conic bundle is rational.
This is an attempt to summarize the talks of the session on Deconfinement.This talk covers the following topics:Elliptic flow,high transverse momentum production,propagation of jets and energy loss,heavy quarqonia in dense QCD matter,phase transition,multiplicity fluctuations,long range correlations, multiparticle production and thermalization
By elaborating a two-dimensional Selberg sieve with asymptotics and equidistributions of Kloosterman sums from $\ell$-adic cohomology, as well as a Bombieri--Vinogradov type mean value theorem for Kloosterman sums in arithmetic progressions, it is proved that for any given primitive Hecke--Maass cusp form of trivial nebentypus, the eigenvalue of the $n$-th Hecke operator does not coincide with the Kloosterman sum $\mathrm{Kl}(1,n)$ for infinitely many squarefree $n$ with at most $100$ prime factors. This provides a partial negative answer to a problem of Katz on modular structures of Kloosterman sums.
Many works, aiming to explain the origin of dark matter or dark energy, consider the existence of hidden (brane)worlds parallel to our own visible world - our usual universe - in a multidimensional bulk. Hidden braneworlds allow for hidden copies of the Standard Model. For instance, atoms hidden in a hidden brane could exist as dark matter candidates. As a way to constrain such hypotheses, the possibility for neutron-hidden neutron swapping can be tested thanks to disappearance-reappearance experiments also known as passing-through-walls neutron experiments. The neutron-hidden neutron coupling $g$ can be constrained from those experiments. While $g$ could be arbitrarily small, previous works involving a $M_4 \times R_1$ bulk, with DGP branes, show that $g$ then possesses a value which is reachable experimentally. It is of crucial interest to know if a reachable value for $g$ is universal or not and to estimate its magnitude. Indeed, it would allow, in a near future, to reject definitively - or not - the existence of hidden braneworlds from experiments. In the present paper, we explore this issue by calculating $g$ for DGP branes, for $M_4 \times S_1/Z_2$, $M_4 \times R_2$ and $M_4 \times T^2$ bulks. As a major result, no disappearance-reappearance experiment would definitively universally rules out the existence of hidden worlds endowed with their own copy of Standard Model particles, excepted for specific scenarios with conditions reachable in future experiments.
In the first part of the present work, the correction to photon emission rate of an oscillating two-level atom in the presence of electromagnetic quantum vacuum field has been investigated for two different configurations: (i) Atom is trapped in the vicinity of a perfect conductor (ii) Atom is trapped between two perfect conductors. In the second part, the correction to the decay rate of an initially excited oscillating two-level atom due to the presence of a perfect conducting surface is found.
Charge radii of Sn, Ba, Yb, and Pb isotopes are calculated within Hartree-Fock-Bogoliubov theory with a Skyrme force and a density-dependent delta-force pairing. We investigate mean field effects of the pairing upon odd-even staggering of isotope shifts. HFB equations are solved in the canonical basis. Odd nuclei are treated in the blocking approximation.
It is shown that a massive Abelian vector boson field can generate the curvature perturbation in the Universe, when coupled non-minimally to gravity, through an RA^2 coupling. The vector boson acts as a curvaton field imposing the curvature perturbation after the end of inflation, without generating a large-scale anisotropy. The parameter space of the model is fully explored, obtaining the relevant bounds on the inflation scale and the decay constant of the vector curvaton.
The accurate determination of transport coefficients in numerical simulations is becoming increasingly important in a wide range of applications. Here we consider the linear response in systems driven away from thermal equilibrium into a non-equilibrium steady state with non-vanishing entropy production rate. A simple derivation of a general response formula is presented. For Markov processes we explicitly construct the conjugate quantities and discuss their relation with known response formulas. Emphasis is put on the formal analogy with thermodynamic potentials and some consequences are discussed.
(Bi1-xSbx)2Se3 thin films have been prepared using molecular beam epitaxy (MBE). We demonstrate the angle-resolved photoemission spectroscopy (ARPES) and transport evidence for the existence of strong and robust topological surface states in this ternary system. Large tunability in transport properties by varying the Sb doping level has also been observed, where insulating phase could be achieved at x=0.5. Our results reveal the potential of this system for the study of tunable topological insulator and metal-insulator transition based device physics.
We present CARMA observations of the three northern unconfirmed galaxy clusters discovered by the PLANCK satellite. We confirm the existence of two massive clusters (PLCKESZ G115.71+17.52 and PLCKESZ G121.11+57.01) at high significance. For these clusters, we present refined centroid locations from the 31 GHz CARMA data, as well as mass estimates obtained from a joint analysis of CARMA and PLANCK data. We do not detect the third candidate, PLCKESZ G189.84-37.24, and place an upper limit on its mass of M500 < 3.2 X 10^(14) M_SUN at 68% confidence. Considering our data and the characteristics of the PLANCK Early Release SZ Catalog, we conclude that this object is likely to be a cold-core object in the plane of our Galaxy. As a result, we estimate the purity of the ESZ Catalog to be greater than 99.5%.
Deep neural networks (DNNs) based methods have achieved great success in single image super-resolution (SISR). However, existing state-of-the-art SISR techniques are designed like black boxes lacking transparency and interpretability. Moreover, the improvement in visual quality is often at the price of increased model complexity due to black-box design. In this paper, we present and advocate an explainable approach toward SISR named model-guided deep unfolding network (MoG-DUN). Targeting at breaking the coherence barrier, we opt to work with a well-established image prior named nonlocal auto-regressive model and use it to guide our DNN design. By integrating deep denoising and nonlocal regularization as trainable modules within a deep learning framework, we can unfold the iterative process of model-based SISR into a multi-stage concatenation of building blocks with three interconnected modules (denoising, nonlocal-AR, and reconstruction). The design of all three modules leverages the latest advances including dense/skip connections as well as fast nonlocal implementation. In addition to explainability, MoG-DUN is accurate (producing fewer aliasing artifacts), computationally efficient (with reduced model parameters), and versatile (capable of handling multiple degradations). The superiority of the proposed MoG-DUN method to existing state-of-the-art image SR methods including RCAN, SRMDNF, and SRFBN is substantiated by extensive experiments on several popular datasets and various degradation scenarios.
Spine spaces can be considered as fragments of a projective Grassmann space. We prove that the structure of lines together with binary coplanarity relation, as well as with binary relation of being in one pencil of lines, is a sufficient system of primitive notions for these geometries. It is also shown that, over a spine space, the geometry of pencils of lines can be reconstructed in terms of the two binary relations.
Recent experiments shown that graphene epitaxially grown on Silicon Carbide (SiC) can exhibit a energy gap of 0.26 eV, making it a promising material for electronics. With an accurate model, we explore the design parameter space for a fully ballistic graphene-on-SiC Tunnel Field-Effect Transistors (TFETs), and assess the DC and high frequency figures of merit. The steep subthreshold behavior can enable I_{ON}/I_{OFF} ratios exceeding 10^4 even with a low supply voltage of 0.15 V, for devices with gatelength down to 30 nm. Intrinsic transistor delays smaller than 1 ps are obtained. These factors make the device an interesting candidate for low-power nanoelectronics beyond CMOS.
We investigate the strong electric current sheet that develops at the tip of the pulsar closed line region through time dependent three-dimensional numerical simulations of a rotating magnetic dipole. We show that curvature radiation from relativistic electrons and positrons in the current sheet may naturally account for several features of the high-energy pulsar emission. We obtain light curves and polarization profiles for the complete range of magnetic field inclination angles and observer orientations, and compare our results to recent observations from the Fermi gamma-ray telescope.
Using 4D, N=1 superfield techniques, a discussion of the 6D sigma-model possessing simple supersymmetry is given. Two such approaches are described. Foremost it is shown that the simplest and most transparent description arises by use of a doublet of chiral scalar superfields for each 6D hypermultiplet. A second description that is most directly related to projective superspace is also presented. The latter necessarily implies the use of one chiral superfield and one nonminimal scalar superfield for each 6D hypermultiplet. A separate study of models of this class, outside the context of projective superspace, is also undertaken.
A drawing of a graph is {\em pseudolinear} if there is a pseudoline arrangement such that each pseudoline contains exactly one edge of the drawing. The {\em pseudolinear crossing number} of a graph $G$ is the minimum number of pairwise crossings of edges in a pseudolinear drawing of $G$. We establish several facts on the pseudolinear crossing number, including its computational complexity and its relationship to the usual crossing number and to the rectilinear crossing number. This investigation was motivated by open questions and issues raised by Marcus Schaefer in his comprehensive survey of the many variants of the crossing number of a graph.
The ratio $R_T$ of $K^+-^{12}C$ to $K^+-d$ cross sections has been calculated microscopically using a boson-exchange $KN$ amplitude in which the $\sigma$ and $\omega$ mesons are dressed by the modifications of the Dirac sea in nuclear matter. In spite of the fact that this dressing leads to a scaling of the mesons effective mass in nuclear matter, the effect on the $R_T$ ratio is found to be weak.
L.Bondesson [1] conjectured that the density of a positive $\alpha$-stable distribution is hyperbolically completely monotone (HCM in short) if and only if $\alpha$ $\le$ 1/2. This was proved recently by P. Bosch and Th. Simon, who also conjectured a strengthened version of this result. We disprove this conjecture as well as a correlated conjecture of Bondesson, while giving a short new proof of the initial conjecture, as a direct consequence of a new algebraic property of HCM and Generalized Gamma convolution densities (GGC in short) which we establish.
Extreme values are considered in samples with random size that has a mixed Poisson distribution being generated by a doubly stochastic Poisson process. We prove some inequalities providing bounds on the rate of convergence in limit theorems for the distributions of max-compound Cox processes.
Photo- and electroproduction of pions and eta-mesons is studied on the nucleon. The formalism of such reactions is presented including polarization degrees of freedom and theoretical approaches are discussed. In particular, the threshold and $\Delta$-resonance region of pion photoproduction is considered and recent developments on low energy theorems (LET) and the E2/C2 quadrupole excitation of the $\Delta$ are presented. For eta photoproduction we show our calculations for the threshold region of the new Mainz experiment and demonstrate the sensitivity of this reaction to the elementary $\eta NN$ coupling and the resonance parameters of the $S_{11}(1535)$. In nuclear applications we point out the importance and advantage of light nuclei as $d$, $^3H$, $^3He$ and $^4He$ for the isospin structure of the reactions as well as for medium effects of the nucleon resonances.
The magnetotransport properties of massless Dirac fermions in a gapless HgTe quantum well are investigated. In samples with narrow channels, a large negative magnetoresistance with a Lorentzian profile is observed, which is interpreted as a manifestation of electron viscosity due to electron-electron interaction. Comparison of experiment with theory yields the shear stress relaxation time of the Dirac fermions caused by electron-electron scattering.
Three presumably unrelated open questions concerning gravity and the structure of the Universe are here discussed: 1) To which extent is Lorentz invariance an exact symmetry ? 2) What is the equation of state of the Universe ? 3) What is the origin of the so-called Pioneer anomaly ?
Recently, a hybrid percolation transitions (HPT) that exhibits both a discontinuous transition and critical behavior at the same transition point has been observed in diverse complex systems. In spite of considerable effort to develop the theory of HPT, it is still incomplete, particularly when the transition is induced by cluster merging dynamics. Here, we aim to develop a theoretical framework of the HPT induced by such dynamics. We find that two correlation-length exponents are necessary for characterizing the giant cluster and finite clusters, respectively. Finite-size scaling method for the HPT is also introduced. The conventional formula of the fractal dimension in terms of the critical exponents is not valid. Neither the giant nor finite clusters are fractals but they have fractal boundaries.
We explore the vertical light distribution as a function of galactocentric radius in the edge-on (i=88) Sd `superthin' galaxy UGC7321. UGC7321 is a low-luminosity spiral (M_B,i=-17.0) with a diffuse, low surface brightness stellar disk and no discernible bulge component. Within 0.25' (725 pc) of the disk center the global luminosity profile of UGC7321 can be reasonably characterized by an exponential function with a scale height h_z=2.9" (140 pc) in H and h_z=3.1" (150 pc) in R, making this among the thinnest galaxy disks know. Near the disk center we derive a ratio of disk scale length to global disk scale height h_r/h_z=14 in both H and R; near the edge of the disk, h_r/h_z=10. At intermediate galactocentric radii (0.25'<r<1.5'), the disk of UGC7321 becomes less peaked than an exponential near the galactic plane. At these radii the vertical luminosity profiles can be well reproduced by a linear combination of two isothermal disk components of differing scale heights. These fits, together with the strong disk color gradients by Matthews, Gallagher, & van Driel (1999), suggest that UGC7321 has multiple disk subcomponents comprised of stellar populations with different ages and velocity dispersions. Thus even examples of the thinnest pure disk galaxies exhibit complex structure and signatures of dynamical heating.
This paper explores a fully unsupervised deep learning approach for computing distance-preserving maps that generate low-dimensional embeddings for a certain class of manifolds. We use the Siamese configuration to train a neural network to solve the problem of least squares multidimensional scaling for generating maps that approximately preserve geodesic distances. By training with only a few landmarks, we show a significantly improved local and nonlocal generalization of the isometric mapping as compared to analogous non-parametric counterparts. Importantly, the combination of a deep-learning framework with a multidimensional scaling objective enables a numerical analysis of network architectures to aid in understanding their representation power. This provides a geometric perspective to the generalizability of deep learning.
We present radio spectral analyses for a sample of 29 radio-quiet (RQ) and three radio-loud (RL) narrow-line Seyfert 1 galaxies (NLS1s) detected with the Australia Telescope Compact Array at both 5.5 GHz and 9.0 GHz. The sample is characterized by L_bol/L_Edd > 0.15. The radio slopes in 25 of the 29 RQ NLS1s are steep (alpha_5.5-9.0 < -0.5), as found in earlier studies of RQ high L_bol/L_Edd AGN. This steep radio emission may be related to AGN-driven outflows, which are likely more prevalent in high L_bol/L_Edd AGN. In two of the three RL NLS1s, the radio slopes are flat or inverted (alpha_5.5-9.0 > -0.5), indicating a compact optically-thick source, likely a relativistic jet. Archival data at 3.0 GHz, 1.4 GHz, and 0.843 GHz are also compiled, yielding a sample of 17 NLS1s detected in three bands or more. In nine objects, the radio spectra flatten at lower frequencies, with median slopes of alpha_5.5-9.0 = -1.21 +/- 0.17, flattening to alpha_3.0-5.5 = -0.97 +/- 0.27, and to alpha_1.4-3.0 = -0.63 +/- 0.16. A parabolic fit suggests a median spectral turnover of ~ 1 GHz, which implies synchrotron self-absorption in a source with a size of only a fraction of 1 pc, possibly a compact wind or a weak jet. Two objects show significant spectral steepening to alpha < -2 above 3 GHz or 5 GHz, which may suggest relic emission from past ejection of radio emitting plasma, of the order of a few years to a few decades ago. Finally, two objects present a single spectral slope consistent with star-forming activity.