ShantanuT01/DACTYL-Pretraining huggingface dataset:
HI line widths are typically interpreted as a measure of ISM turbulence, which is potentially driven by star formation. In an effort to better understand the possible connections between line widths and star formation, we have characterized \hi{} kinematics in a sample of nearby dwarf galaxies by co-adding line-of-sight spectra after removing the rotational velocity to produce an average, global \hi{} line profile. These "superprofiles" are composed of a central narrow peak (~6-10 km/s) with higher-velocity wings to either side that contain ~10-15% of the total flux. The superprofiles are all very similar, indicating a universal global HI profile for dwarf galaxies. We compare characteristics of the superprofiles to various galaxy properties, such as mass and measures of star formation (SF), with the assumption that the superprofile represents a turbulent peak with energetic wings to either side. We use these quantities to derive average scale heights for the sample galaxies. When comparing to physical properties, we find that the velocity dispersion of the central peak is correlated with $<\Sigma_\mathrm{HI}>$. The fraction of mass and characteristic velocity of the high velocity wings are correlated with measures of SF, consistent with the picture that SF drives surrounding HI to higher velocities. While gravitational instabilities provide too little energy, the SF in the sample galaxies does provide enough energy through supernovae, with realistic estimates of the coupling efficiency, to produce the observed superprofiles.
Weyl semimetal (WSM) feature tilted Dirac cones and can be type I or II depending on the magnitude of the tilt parameter ($C$). The boundary between the two types is at $C=1$ where the cones are tipped and there is a Lifshitz transition. The topological charge of a WSM is one. In multi-Weyl it can be two or more depending on the value of the winding number $J$. We calculate the absorptive part of the AC optical conductivity both along the tilt direction ($\sigma_{zz}$) and perpendicular to it ($\sigma_{xx}$) as a function of the tilt ($C$) and chemical potential ($\mu$). For zero tilt there is a discontinuous rise in both $\sigma_{xx}$ and $\sigma_{zz}$ at photon energy $\Omega=2\mu$ followed by the usual linear in $\Omega$ law for $\sigma_{xx}$ at $J=1,2$ and $\sigma_{zz}$ at $J=1$. For $J=2$ and $\sigma_{zz}$ the interband background is constant rather than linear in $\Omega$. For type I there is a readjustment of optical spectral weight as the tilt is increased. The absorption starts from zero at $2\mu/(1+C)$ and then rises in a quasilinear fashion till it merge with the usual undoped untilted interband background at $2\mu/(1-C)$. The discontinuous rise at twice the chemical potential of the untilted case is lost. For type II the interband background of the undoped untilted case is never recovered. For noncentrosymmetric materials the energies of a pair of opposite chirality Weyl nodes become shifted by $\pm Q_{0}$ and this leads to two separate absorption edges corresponding to the effective chemical potential of each of the two nodes at $2(\mu+\chi Q_{0})$ depending on chirality $\chi=\pm$. We provide analytic expressions for the conductivity in this case which depend only on the ratio $Q_{0}/\mu$ and tilt when plotted against $\Omega/\mu$. The signature of finite energy shift $Q_{0}$ is more pronounced for $\sigma_{zz}$ and $J=2$ than for the other cases.
New neutron diffraction and inelastic neutron scattering experiments on Ba2CuGe2O7 suggest that the previously suggested model for the magnetism of this material (an ideal sinusoidal spin spiral, stabilized by isotropic exchange and Dzyaloshinskii-Moriya interactions) needs to be refined. Both new and previously published experimental results can be quantitatively explained by taking into account the Shekhtman-Entin-Wohlman-Aharony (SEA) term, a special anisotropy term that was predicted to always accompany Dzyaloshinskii-Moriya interactions in insulators. Our experimental results present the first clear evidence to that SEA interactions can lead to substantial observable effects in a real magnetic system.
We present the complete scheme of the application of the one-and two dimensional subspace and subgroups method to five-dimensional gravity with a $G_{3}$ group of motion. We do so in the space time and in the potential space formalisms. From this method one obtains the Kramer, Belinsky-Ruffini, Dobiasch-Maison, Cl\'{e}ment, Gross-Perry-Sorkin solutions etc. as special cases.
We generalize an already proposed protocol for quantum state transfer to spin chains of arbitrary spin. An arbitrary unknown $d-$ level state is transferred through a chain with rather good fidelity by the natural dynamics of the chain. We compare the performance of this protocol for various values of $d$. A by-product of our study is a much simpler method for picking up the state at the destination as compared with the one proposed previously. We also discuss entanglement distribution through such chains and show that the quality of entanglement transition increases with the number of levels $d$.
We present an overview of a theory of complex dimensions of self-similar fractal strings, and compare this theory to the theory of varieties over a finite field from the geometric and the dynamical point of view. Then we combine the several strands to discuss a possible approach to establishing a cohomological interpretation of the complex dimensions.
We report the first results from the Hubble Infrared Pure Parallel Imaging Extragalactic Survey, which utilizes the pure parallel orbits of the Hubble Space Telescope to do deep imaging along a large number of random sightlines. To date, our analysis includes 26 widely separated fields observed by the Wide Field Camera 3, which amounts to 122.8 sq.arcmin in total area. We have found three bright Y098-dropouts, which are candidate galaxies at z >~ 7.4. One of these objects shows an indication of peculiar variability and its nature is uncertain. The other two objects are among the brightest candidate galaxies at these redshifts known to date L>2L*. Such very luminous objects could be the progenitors of the high-mass Lyman break galaxis (LBGs) observed at lower redshifts (up to z~5). While our sample is still limited in size, it is much less subject to the uncertainty caused by "cosmic variance" than other samples because it is derived using fields along many random sightlines. We find that the existence of the brightest candidate at z~7.4 is not well explained by the current luminosity function (LF) estimates at z~8. However, its inferred surface density could be explained by the prediction from the LFs at z~7 if it belongs to the high-redshift tail of the galaxy population at z~7.
We consider the porous medium equation in an exterior two-dimensional domain which excludes a hole, with zero Dirichlet data on its boundary. Gilding and Goncerzewicz proved in [Gilding-Goncerzewicz-2007] that in the far field scale, $x=\xi t^{\frac1{2m}}/(\log t)^{\frac{m-1}{2m}}$, $\xi\ne 0$, solutions to this problem with an integrable and compactly supported initial data behave as an instantaneous point-source solution for the equation with a variable mass that decays to 0 in a precise way, determined by the initial data and the hole. However, their result does not say much about the behavior when $|x|=o\big(t^{\frac1{2m}}/(\log t)^{\frac{m-1}{2m}}\big)$, in the so called near field scale, except that the solution is $o\big((t\log t)^{-\frac1m}\big)$ there. In particular, it does not give a sharp decay rate, neither a nontrivial asymptotic profile, on compact sets. In this paper we characterize the large time behavior in such scale, thus completing the results of [Gilding-Goncerzewicz-2007].
We analyze how predictions of cosmological models depend on a choice of described observational data, restrictions on flatness,   and how this choice can alleviate the $H_0$ tension. These effects are demonstrated in the $w$CDM model in comparison with the standard $\Lambda$CDM model. We describe the Pantheon sample observations of Type Ia supernovae, 31 Hubble parameter data points $H(z)$ from cosmic chronometers, the extended sample with 57 $H(z)$ data points and observational manifestations of cosmic microwave background radiation (CMB).   For the $w$CDM and $\Lambda$CDM models in the flat case and with spatial curvature we calculate $\chi^2$ functions for all observed data in different combinations, estimate optimal values of model parameters and their expected intervals. For both considered models the results essentially depend on a choice of data sets. In particular, for the $w$CDM model with $H(z)$ data, supernovae and CMB the $1\sigma$ estimations may vary from $H_0=67.52^{+0.96}_{-0.95}$ km\,/(s$\cdot$Mpc) (for all $N_H=57$ Hubble parameter data points) up to $H_0=70.87^{+1.63}_{-1.62}$ km\,/(s$\cdot$Mpc) for the flat case ($k=0$) and $N_H=31$. These results might be a hint how to alleviate the problem of $H_0$ tension: different estimates of the Hubble constant may be connected with filters and a choice of observational data.
The ultraviolet (UV) emission of stellar flares may have a pivotal role in the habitability of rocky exoplanets around low-mass stars. Previous studies have used white-light observations to calibrate empirical models which describe the optical and UV flare emission. However, the accuracy of the UV predictions of models have previously not been tested. We combined TESS optical and GALEX UV observations to test the UV predictions of empirical flare models calibrated using optical flare rates of M stars. We find that the canonical 9000 K blackbody model used by flare studies underestimates the GALEX NUV energies of field age M stars by up to a factor of 6.5$\pm$0.7 and the GALEX FUV energies of fully convective field age M stars by 30.6$\pm$10.0. We calculated energy correction factors that can be used to bring the UV predictions of flare models closer in line with observations. We calculated pseudo-continuum flare temperatures that describe both the white-light and GALEX NUV emission. We measured a temperature of 10,700 K for flares from fully convective M stars after accounting for the contribution from UV line emission. We also applied our correction factors to the results of previous studies of the role of flares in abiogenesis. Our results show that M stars do not need to be as active as previously thought in order to provide the NUV flux required for prebiotic chemistry, however we note that flares will also provide more FUV flux than previously modelled.
We study a conserved mass aggregation model with mass-dependent fragmentation in one dimension. In the model, the whole mass $m$ of a site isotropically diffuse with unit rate. With rate $\omega$, a mass $m^{\lambda}$ is fragmented from the site and moves to a randomly selected nearest neighbor site. Since the fragmented mass is smaller than the whole mass $m$ of a site for $\lambda < 1$, the on-site attractive interaction exists for the case. For $\lambda = 0$, the model is known to undergo the condensation phase transitions from a fluid phase into a condensed phase as the density of total masses ($\rho$) increases beyond a critical density $\rho_c$. For $0< \lambda <1$, we numerically confirm for several values of $\omega$ that $\rho_c$ diverges with the system size $L$. Hence in thermodynamic limit, the condensed phase disappears and no transitions take place in one dimension. We also explain that there are no transitions in any dimensions.
We present a spectral analysis of a brief Chandra/HETG observation of the neutron star low-mass X-ray binary GX~340+0. The high-resolution spectrum reveals evidence of ionized absorption in the Fe K band. The strongest feature, an absorption line at approximately 6.9 keV, is required at the 5 sigma level of confidence via an F-test. Photoionization modeling with XSTAR grids suggests that the line is the most prominent part of a disk wind with an apparent outflow speed of v = 0.04c. This interpretation is preferred at the 4 sigma level over a scenario in which the line is H-like Fe XXVI at a modest red-shift. The wind may achieve this speed owing to its relatively low ionization, enabling driving by radiation pressure on lines; in this sense, the wind in GX 340+0 may be the stellar-mass equivalent of the flows in broad absorption line quasars (BALQSOs). If the gas has a unity volume filling factor, the mass ouflow rate in the wind is over 10^-5 Msun/year, and the kinetic power is nearly 10^39 erg/s (or, 5-6 times the radiative Eddington limit for a neutron star). However, geometrical considerations - including a small volume filling factor and low covering factor - likely greatly reduce these values.
Strong and fragile glass relaxation behaviours are obtained simply changing the constraints of the kinetically constrained Ising chain from symmetric to purely asymmetric. We study the out-of-equilibrium dynamics of those two models focusing on the Kovacs effect and the fluctuation--dissipation relations. The Kovacs or memory effect, commonly observed in structural glasses, is present for both constraints but enhanced with the asymmetric ones. Most surprisingly, the related fluctuation-dissipation (FD) relations satisfy the FD theorem in both cases. This result strongly differs from the simple quenching procedure where the asymmetric model presents strong deviations from the FD theorem.
We compute the Z-rank of the subgroup of elements of the multiplicative group of a number field K that are norms from every finite level of the cyclotomic Z{\ell}-extension of K. Thus we compare its {\ell}-adification with the group of logarithmic units of K. By the way we point out an easy proof of the Gross-Kuz'min conjecture for {\ell}-undecomposed extensions of abelian fields.
We used resonant inelastic x-ray scattering to reveal the nature of magnetic interactions in Sr2IrO4, a 5d transition-metal oxide with a spin-orbit entangled ground state and Jeff=1/2 magnetic momemts, referred to as 'isospins'. The magnon dispersion in Sr2IrO4 is well described by an antiferromagnetic Heisenberg model with isospin one-half moments on a square lattice, which renders the low-energy effective physics of Sr2IrO4 much akin to that in superconducting cuprates. This is further supported by the observation of exciton modes in Sr2IrO4 whose dispersion is strongly renormalized by magnons, which can be understood by analogy to the hole propagation in the background of antiferromagnetically ordered spins in the cuprates.
We show how the concept of quantum open system and the methods in non-equilibrium statistical mechanics can be usefully applied to studies of quantum statistical processes in the early universe. We first sketch how noise, fluctuation, dissipation and decoherence processes arise in a wide range of cosmological problems. We then focus on the origin and nature of noise in quantum fields and spacetime dynamics. We introduce the concept of geometrodynamic noise and suggest a statistical mechanical definition of gravitational entropy. We end with a brief discussion of the theoretical appropriateness to view the physical universe as an open system.
We establish the local existence and uniqueness of solutions to the free-boundary ideal compressible magnetohydrodynamic equations with surface tension in three spatial dimensions by a suitable modification of the Nash--Moser iteration scheme. The main ingredients in proving the convergence of the scheme are the tame estimates and unique solvability of the linearized problem in the anisotropic Sobolev spaces $H_*^m$ for $m$ large enough. In order to derive the tame estimates, we make full use of the boundary regularity enhanced from the surface tension. The unique solution of the linearized problem is constructed by designing some suitable $\varepsilon$--regularization and passing to the limit $\varepsilon\to 0$.
We present multiband photometric observations of three spiral galaxies selected in a sample suited for the study of young stellar groupings and their relationship with the parent galaxy and the galactic environment. Star forming regions have been identified using an objective technique based on a multivariate statistical analysis. Maps of young star groupings are given for each galaxy. The luminosity functions of the young star group populations show a remarkable similarity with a slope in the range -1.52 to -1.33 range. The size distributions peak around the classical 100pc value of the Local Group associations for two out of the three galaxies. NGC 1058 shows smaller associations (peak at about 50pc). The total number of young groups per unit B absolute luminosity of the galaxy is significantly greater in UGC 12732. The activity of star formation is in all three galaxies clearly stronger in the central regions.
In inhomogeneous cosmology, restricting attention to an irrotational dust matter model, backreaction arises in terms of the deviation of the averaged spatial scalar curvature from a constant-curvature model on some averaging domain $D$, $W_D$, and the kinematical backreaction $Q_D$. These backreaction variables can be modeled as an effective scalar field, called the `morphon field'. The general cosmological equations still need a closure condition to be solved. A simple example is the class of scaling solutions where $W_D$ and $Q_D$ are assumed to follow a power law of the volume scale factor $a_D$. But while they can describe models of quintessence, these and other models still assume the existence of dark matter in addition to the known sources. Going beyond scaling solutions by using a model for structure formation that we argue is reasonably generic, we investigate the correspondence between the morphon field and fundamental scalar field dark matter models, in order to describe dark matter as an effective phenomenon arising from kinematical backreaction and the averaged spatial curvature of the inhomogeneous Universe. While we find significant differences with those fundamental models, our main result is that the energy budget on typical collapsing domains is provided by curvature and matter in equal parts already around the turn-around time, leading to curvature dominance thereafter and increasing to a curvature contribution of $3/4$ of the energy budget at the onset of virialization. Kinematical backreaction is subdominant at early stages, but its importance rises quickly after turn-around and dominates the curvature contribution in the final phase of the collapse. We conclude that backreaction can indeed mimic dark matter (in the energy budget) during the collapse phase of megaparsec-scale structures.
Noscale supersymmetry (SUSY) breaking model is investigated in the minimal extension of the minimal supersymmetric standard model (MSSM) with a gauged U(1)_{B-L} symmetry. We specifically consider a unification-inspired model with the gauge groups SU(3)_{C} \times SU(2)_{L} \times U(1)_Y \times U(1)_{B-L} \subset SU(5) \times U(1)_{5} for illustration. While the noscale boundary condition at the grand unification scale (M_{G}\simeq 2\times 10^{16} GeV) in the MSSM is not consistent with phenomenological constraints, we show that it is if the gaugino of the U(1)_{5} multiplet is several times heavier than the gauginos of the MSSM. However, if SU(5) \times U(1)_{5} is further embedded in a larger simple group, e.g. SO(10), the noscale boundary condition at M_{G} is inconsistent with phenomenological constraints. If we relax the noscale boundary condition and allow non-zero soft scalar masses for the Higgs fields which spontaneously break the U(1)_{5} symmetry, the resultant spectrum of SUSY particles becomes consistent with all the phenomenological constraints, even if we impose the GUT relation on the gauge coupling and the gaugino mass of the U(1)_{5}. In this case, the SUSY CP problem is also solved, since the condition B\mu =0 at the boundary can be imposed consistently with the electroweak symmetry breaking.
We prove that two Aleksandrov solutions of a generated prescribed Jacobian equation have the same gradients at points where they are both differentiable. For the optimal transportation case where two solutions can be translated to agree at a point without changing the $g$-subdifferential at that point, we recover the uniqueness up to a constant of solutions. For the general case, our result is a new proof with less regularity assumptions of a key theorem recently used to prove the uniqueness of solutions.
In this paper, we study the asymptotic decay properties for defocusing semilinear wave equations in $\mathbb{R}^{1+2}$ with pure power nonlinearity. By applying new vector fields to null hyperplane, we derive improved time decay of the potential energy, with a consequence that the solution scatters both in the critical Sobolev space and energy space for all $p>1+\sqrt{8}$. Moreover combined with Br\'{e}zis-Gallouet-Wainger type of logarithmic Sobolev embedding, we show that the solution decays pointwise with sharp rate $t^{-\frac{1}{2}}$ when $p>\frac{11}{3}$ and with rate $t^{ -\frac{p-1}{8}+\epsilon }$ for all $1<p\leq \frac{11}{3}$. This in particular implies that the solution scatters in energy space when $p>2\sqrt{5}-1$.
We present the results of a survey of interstellar O~{\small VI} absorption in the Milky Way (MW) towards {69} stars in the Large Magellanic Cloud (LMC) obtained with the \textit{Far Ultraviolet Spectroscopic Explorer (FUSE)}. The integrated MW O~{\small VI} column densities log N(O~{\small VI}) are in the range from 13.68 to 14.73 with a mean of {14.26$_{-0.09}^{+0.07}$} atoms cm$^{-2}$. The O~{\small VI} exponential scale height is found to be {2.28$\pm$1.06} kpc. The O~{\small VI} column density correlates with the Doppler parameter $\it b$. The O~{\small VI} velocity dispersion ranges from {14.0 to 91.6 with an average value of 62.7 km s$^{-1}$}. These high values of velocity dispersion reveal the effect of turbulence, multiple velocity components and collision on broad O~{\small VI} profiles. There is a significant variation of O~{\small VI} column density on all scales studied {(0.0025$\degr$ - 6.35$\degr$)}. The smallest scale for which O~{\small VI} column density variations has been found is {$\bigtriangleup \theta$ $\sim$~9$\arcsec$}. Comparison of the O~{\small VI} velocity profiles with Fe~{\small II} indicates the presence of intermediate velocity cloud (IVC) and/or high velocity cloud (HVC) components in the O~{\small VI} absorption.
Quantum mechanics demands that the act of measurement must affect the measured object. When a linear amplifier is used to continuously monitor the position of an object, the Heisenberg uncertainty relationship requires that the object be driven by force impulses, called back-action. Here we measure the back-action of a superconducting single-electron transistor (SSET) on a radiofrequency nanomechanical resonator. The conductance of the SSET, which is capacitively coupled to the resonator, provides a sensitive probe of the latter's position;back-action effects manifest themselves as an effective thermal bath, the properties of which depend sensitively on SSET bias conditions. Surprisingly, when the SSET is biased near a transport resonance, we observe cooling of the nanomechanical mode from 550mK to 300mK-- an effect that is analogous to laser cooling in atomic physics. Our measurements have implications for nanomechanical readout of quantum information devices and the limits of ultrasensitive force microscopy (such as single-nuclear-spin magnetic resonance force microscopy). Furthermore, we anticipate the use of these backaction effects to prepare ultracold and quantum states of mechanical structures, which would not be accessible with existing technology.