ShantanuT01/DACTYL-Pretraining huggingface dataset:
The similarity theory of stellar structure is used to study the properties of very massive stars when one can neglect all the sources of opacity except for the Thomson scattering. The dimensionless internal structure of such stars is practically independent of the energy generation law.   It is shown that the mass-luminosity relation can be approximated by an analytical expression which is virtually universal regarding the chemical composition and energy generation law. A detailed comparison with the   Eddington standard model is given. The application of the obtained results to the observations of massive stars is briefly discussed.
We study scenarios in the minimal and next-to minimal supersymmetric models in which the lightest CP-even Higgs boson can have mass below the 114 GeV standard model LEP limit by virtue of reduced ZZ coupling due to substantial mixing among the Higgs bosons. We pay particular attention to the size of corrections from superpartners needed for these scenarios to be viable and point to boundary conditions at large scales which lead to these scenarios while at the same time keeping electroweak fine tuning modest in size. We find that naturalness of electroweak symmetry breaking in the mixed-Higgs scenarios of both models points to the same region of soft supersymmetry breaking terms, namely those leading to large mixing in the stop sector at the electroweak scale, especially if we also require that the lightest CP-even Higgs explains the Higgs-like LEP events at about 98 GeV.
Ferroelectric photovoltaic materials are an alternative to semiconductor-based photovoltaics and offer the advantage of above bandgap photovoltage generation. However, there are few known compounds, and photovoltaic efficiencies remain low. Here, we report the discovery of a photovoltaic effect in undoped lead magnesium niobate-lead titanate crystal and a significant improvement in the photovoltaic response under suitable electric fields and temperatures. The photovoltaic effect is maximum near the electric-field-driven ferroelectric dipole reorientation, and increases threefold near the Curie temperature. Moreover, at ferroelectric saturation, the photovoltaic response exhibits clear remanent and transient effects. The transient-remanent combinations together with electric and thermal tuning possibilities indicate photoferroelectric crystals as emerging elements for photovoltaics and optoelectronics, relevant to all-optical information storage and beyond.
Some time ago it was pointed out that the presence of cosmological components could affect the propagation of gravitational waves (GW) beyond the usual cosmological redshift and that such effects might be observable in pulsar timing arrays. These analyses were done at leading order in the Hubble constant $H_0$, which is proportional to $\Lambda^{1/2}$ and $\rho_i^{1/2}$ ($\rho_i$ being the various cosmological fluid densities). In this work, we study in detail the propagation of metric perturbations on a Schwarzschild-de Sitter (SdS) background, close to the place where GW are produced, and obtain solutions that incorporate corrections linear in $\rho_i$ and $\Lambda$. At the next-to-leading order the corrections do not appear in the form of $H_0$ thus lifting the degeneracy among the various cosmological components. We also determine the leading corrections proportional to the mass of the final object; they are very small for the distances considered in pulsar timing arrays but may be of relevance in other cases. When transformed into comoving coordinates, the ones used in cosmological measurements, this SdS solution does satisfy the perturbation equations in a Friedmann-Lema\^itre-Robertson-Walker metric up to and including $\Lambda^{3/2}$ terms. This analysis is then extended to the other cosmological fluids, allowing us to consider GW sources in the Gpc range. Finally, we investigate the influence of these corrections in pulsar timing arrays observations.
We present colour-colour diagrams of detected sources in the Herschel-ATLAS Science Demonstration Field from 100 to 500 microns using both PACS and SPIRE. We fit isothermal modified black bodies to the spectral energy distribution (SED) to extract the dust temperature of sources with counterparts in Galaxy And Mass Assembly (GAMA) or SDSS surveys with either a spectroscopic or a photometric redshift. For a subsample of 330 sources detected in at least three FIR bands with a significance greater than 3 $\sigma$, we find an average dust temperature of $(28 \pm 8)$K. For sources with no known redshift, we populate the colour-colour diagram with a large number of SEDs generated with a broad range of dust temperatures and emissivity parameters, and compare to colours of observed sources to establish the redshift distribution of this sample. For another subsample of 1686 sources with fluxes above 35 mJy at 350 microns and detected at 250 and 500 microns with a significance greater than 3$\sigma$, we find an average redshift of $2.2 \pm 0.6$.
Over the past decade, the numerical modeling of the magnetic field evolution in astrophysical scenarios has become an increasingly important field. In the crystallized crust of neutron stars the evolution of the magnetic field is governed by the Hall induction equation. In this equation the relative contribution of the two terms (Hall term and Ohmic dissipation) varies depending on the local conditions of temperature and magnetic field strength. This results in the transition from the purely parabolic character of the equations to the hyperbolic regime as the magnetic Reynolds number increases, which presents severe numerical problems. Up to now, most attempts to study this problem were based on spectral methods, but they failed in representing the transition to large magnetic Reynolds numbers. We present a new code based on upwind finite differences techniques that can handle situations with arbitrary low magnetic diffusivity and it is suitable for studying the formation of sharp current sheets during the evolution. The code is thoroughly tested in different limits and used to illustrate the evolution of the crustal magnetic field in a neutron star in some representative cases. Our code, coupled to cooling codes, can be used to perform long-term simulations of the magneto-thermal evolution of neutron stars.
A recently proposed super-heat-kernel technique is applied to heavy baryon chiral perturbation theory with two flavours. A previous result for the one-loop divergences of the pion-nucleon system is confirmed, giving at the same time an impressive demonstration of the efficiency of the new method. The cumbersome and tedious calculations of the conventional approach are now reduced to a few simple algebraic manipulations. The present computational scheme is not restricted to chiral perturbation theory, but can easily be applied or extended to any (in general non-renormalizable) theory with boson-fermion interactions.
The wavelength and the propagation length of the edge magnetoplasmons, running along the edge of a two-dimensional electron layer in a semiconductor quantum-well structure are theoretically studied as a function of frequency, magnetic field, electron density, mobility, and geometry of the structure. The results are intended to be used for analysis and optimization of operation of recently invented quantum-well microwave spectrometers operating at liquid-nitrogen temperatures (I. V. Kukushkin {\em et al}, Appl. Phys. Lett. {\bf 86}, 044101 (2005)).
A possible connection between the flavour structure of the charged fermions and the large $\nu_\mu-\nu_\tau$ mixing motivates an ansatz for the neutrino mass matrix with a dominant block. We distinguish between a general form and the specific forms of the ansatz, and concentrate on the cases of phenomenological interest. The general form can incorporate an observable amount of CP violation in the leptonic sector. Only specific forms can incorporate the Mikheyev-Smirnov-Wolfenstein solutions for solar neutrinos, with small or large mixing angles. Other specific variants explain the Los Alamos neutrino anomaly, or provide a two-neutrino hot dark matter component.
Schramm-Loewner Evolutions (SLEs) describe a one-parameter family of growth processes in the plane that have particular conformal invariance properties. For instance, SLE can define simple random curves in a simply connected domain. In this paper we are interested in questions pertaining to the definition of several SLEs in a domain (i.e. several random curves). In particular, one derives infinitesimal commutation conditions, discuss some elementary solutions, study integrability conditions following from commutation and show how to lift these infinitesimal relations to global relations in simple cases. The situation in multiply-connected domains is also discussed.
To recognize textures many methods have been developed along the years. However, texture datasets may be hard to be classified due to artefacts such as a variety of scale, illumination and noise. This paper proposes the application of binary distance transform on the original dataset to add information to texture representation and consequently improve recognition. Texture images, usually in grayscale, suffers a binarization prior to distance transform and one of the resulted images are combined with original texture to improve the amount of information. Four datasets are used to evaluate our approach. For Outex dataset, for instance, the proposal outperforms all rates, improvements of an up to 10\%, compared to traditional approach where descriptors are applied on the original dataset, showing the importance of this approach.
We analyze the spectral moments of the V-A two-point correlation function. Using all known short-distance constraints and the most recent experimental data from tau decays, we determine the lowest spectral moments, trying to assess the uncertainties associated with the so-called violations of quark-hadron duality. We have generated a large number of "acceptable" spectral functions, satisfying all conditions, and have used them to extract the wanted hadronic parameters through a careful statistical analysis. We obtain accurate values for the ChPT couplings L10 and C87, and a realistic determination of the dimension six and eight contributions in the operator product expansion, O6=(-5.4^{+3.6}_{-1.6})*10^-3 GeV^6 and O8=(-8.9^{+12.6}_{-7.4})*10^-3 GeV^8, showing that the duality-violation effects have been usually underestimated in previous literature.
We review in generality why time-independent endstates can be reached in black hole and collapse simulations, with and without excision. We characterise the Killing states of the Bona-Masso slicing condition with time derivative along the normals to the slice ("BMn") as solutions of a mixed elliptic/hyperbolic differential equation on the slice. We show numerically that these steady states can be reached as end states from typical initial data with excision but can be reached with the puncture method only if the puncture is not numerically well resolved. During the evolution, BMn slicings often form gauge shocks. It may be that these are not seen in current 3D simulations only through lack of resolution, although we expect that they can be avoided with some care. Finally we point out that excision with BMn as currently implemented is ill-posed and therefore not expected to converge; this can be cured. In technical appendixes, we derive the equations of pure gauge systems on a fixed spacetime, and bring the BSSN/NOR equations into 3-dimensional tensor form suitable for multiple coordinate patches or spherical polar coordinates.
The thermal stability of accretion disk and the possibility to see a limit-cycle behaviour strongly depends on the ability of the disk plasma to cool down. Various processes connected with radiation-matter interaction appearing in hot accretion disk plasma contribute to opacity. For the case of geometrically thin and optically thick accretion disk, we can estimate the influence of several different components of function \kappa, given by the Roseland mean. In the case of high temperatures, the electron Thomson scattering is dominant. At lower temperatures atomic processes become important. The slope d log \kappa/d log T can have locally stabilizing or destabilizing effect on the disk. Although the local MHD simulation postulate the stabilizing influence of the atomic processes, only the global time-dependent model can reveal the global disk stability range estimation. This is due to global diffusive nature of that processes. In this paper, using previously tested GLADIS code with modified prescription of the viscous dissipation, we examine the stabilizing effect of the Iron Opacity Bump.
In this paper we study existence and spectral properties for weak solutions of Neumann and Dirichlet problems associated to second order linear degenerate elliptic partial differential operators $X$, with rough coefficients of the form $$X=-\text{div}(P\nabla )+{\bf HR}+{\bf S^\prime G} +F$$ in a geometric homogeneous space setting where the $n\times n$ matrix function $P=P(x)$ is allowed to degenerate. We give a maximum principle for weak solutions of $Xu\leq 0$ and follow this with a result describing a relationship between compact projection of the degenerate Sobolev space $QH^{1,p}$ into $L^q$ and a Poincar\'e inequality with gain adapted to $Q$.
We present a Born-Infeld type theory to describe the evolution of p-branes propagating in an N = (p+2)-dimensional Minkowski spacetime. The expansion of the BI-type volume element gives rise to the (p+1) Lovelock brane invariants associated with the worldvolume swept out by the brane. Contrary to the Lovelock theory in gravity, the number of Lovelock brane Lagrangians differs in this case, depending on the dimension of the worldvolume as a consequence that we consider the embedding functions, instead of the metric, as the field variables. This model depends on the intrinsic and the extrinsic geometries of the worldvolume and in consequence is a second-order theory as shown in the main text. A classically equivalent action is discussed and we comment on its Weyl invariance in any dimension which naturally requires the introduction of some auxiliary fields.
We present near-infrared spectroscopic observations from VLT ISAAC of thirteen 250\mu m-luminous galaxies in the CDF-S, seven of which have confirmed redshifts which average to <z > = 2.0 \pm 0.4. Another two sources of the 13 have tentative z > 1 identifications. Eight of the nine redshifts were identified with H{\alpha} detection in H- and K-bands, three of which are confirmed redshifts from previous spectroscopic surveys. We use their near-IR spectra to measure H{\alpha} line widths and luminosities, which average to 415 \pm 20 km/s and 3 \times 10^35 W (implying SFR(H{\alpha})~200 M_\odot /yr), both similar to the H{\alpha} properties of SMGs. Just like SMGs, 250 \mu m-luminous galaxies have large H{\alpha} to far-infrared (FIR) extinction factors such that the H{\alpha} SFRs underestimate the FIR SFRs by ~8-80 times. Far-infrared photometric points from observed 24\mu m through 870\mu m are used to constrain the spectral energy distributions (SEDs) even though uncertainty caused by FIR confusion in the BLAST bands is significant. The population has a mean dust temperature of Td = 52 \pm 6 K, emissivity {\beta} = 1.73 \pm 0.13, and FIR luminosity LFIR = 3 \times 10^13 L_\odot. Although selection at 250\mu m allows for the detection of much hotter dust dominated HyLIRGs than SMG selection (at 850\mu m), we do not find any >60 K 'hot-dust' HyLIRGs. We have shown that near-infrared spectroscopy combined with good photometric redshifts is an efficient way to spectroscopically identify and characterise these rare, extreme systems, hundreds of which are being discovered by the newest generation of IR observatories including the Herschel Space Observatory.
Valley degrees of freedom offer a potential resource for quantum information processing if they can be effectively controlled. We discuss an optical approach to this problem in which intense light breaks electronic symmetries of a two-dimensional Dirac material. The resulting quasienergy structures may then differ for different valleys, so that the Floquet physics of the system can be exploited to produce highly polarized valley currents. This physics can be utilized to realize a valley valve whose behavior is determined optically. We propose a concrete way to achieve such valleytronics in graphene as well as in a simple model of an inversion-symmetry broken Dirac material. We study the effect numerically and demonstrate its robustness against moderate disorder and small deviations in optical parameters.
The detailed formulation for loop quantum cosmology (LQC) in the Bianchi I model with a massless scalar field was recently constructed. In this paper, its effective dynamics with the LQC discreteness corrections is studied and the equations of motion are analytically solved, showing that the big bang singularity is replaced by the big bounces, which take place up to three times, once in each diagonal direction, whenever each of the area scale factors approaches its critical value in the Planck regime measured by the reference of the scalar field momentum.
Since the temperature of a typical Schwarzschild black hole is very low, some doubts are raised about whether the fluctuations of the black hole can be treated thermodynamically. It is shown that this is not the case: the thermodynamic fluctuations of a black hole are considerably larger than the corresponding quantum fluctuations. Moreover the ratio of the mean square thermodynamic fluctuation to the corresponding quantum fluctuation can be interpreted as a number of the effective constituents of a black hole.
We show that at large magnetic Prandtl numbers, the Lorentz force does work on the flow at small scales and drives fluid motions, whose energy is dissipated viscously. This situation is opposite to that in a normal dynamo, where the flow does work against the Lorentz force. We compute the spectral conversion rates between kinetic and magnetic energies for several magnetic Prandtl numbers and show that normal (forward) dynamo action occurs on large scales over a progressively narrower range of wavenumbers as the magnetic Prandtl number is increased. At higher wavenumbers, reversed dynamo action occurs, i.e., magnetic energy is converted back into kinetic energy at small scales. We demonstrate this in both direct numerical simulations forced by volume stirring and in large eddy simulations of solar convectively driven small-scale dynamos. Low density plasmas such as stellar coronae tend to have large magnetic Prandtl numbers, i.e., the viscosity is large compared with the magnetic diffusivity. The regime in which viscous dissipation dominates over resistive dissipation for large magnetic Prandtl numbers was also previously found in large eddy simulations of the solar corona, i.e., our findings are a more fundamental property of MHD that is not just restricted to dynamos. Viscous energy dissipation is a consequence of positive Lorentz force work, which may partly correspond to particle acceleration in close-to-collisionless plasmas. This is, however, not modeled in the MHD approximation employed. By contrast, resistive energy dissipation on current sheets is expected to be unimportant in stellar coronae.
Thompson scattering of cosmic microwave background (CMB) photons off of free electrons during the reionization epoch induces a correlation between the distribution of galaxies and the polarization pattern of the CMB, the magnitude of which is proportional to the quadrupole moment of radiation at the time of scattering. Since the quadrupole moment generated by gravitational waves (GWs) gives rise to a different polarization pattern than that produced by scalar modes, one can put interesting constraints on the strength of GWs on large scales by cross-correlating the small scale galaxy distribution and CMB polarization. We use this method together with Fisher analysis to predict how well future surveys can measure the tensor-to-scalar ratio $r$. We find that with a future CMB experiment with detector noise Delta_P = 2 mu K-arcmin and a beam width theta_FWHM = 2' and a future galaxy survey with limiting magnitude I<25.6 one can measure the tensor-to-scalar ratio with an error sigma_r \simeq 0.09. To measure r \approx 0.01, however, one needs Delta_P \simeq 0.5 mu K-radian and theta_FWHM \simeq 1'. We also investigate a few systematic effects, none of which turn out to add any biases to our estimators, but they increase the error bars by adding to the cosmic variance. The incomplete sky coverage has the most dramatic effect on our constraints on r for large sky cuts, with a reduction in signal-to-noise smaller than one would expect from the naive estimate (S/N)^2 \propto f_sky. Specifically, we find a degradation factor of f_deg=0.32 \pm 0.01 for a sky cut of |b|>10^\circ (f_sky=0.83) and f_deg=0.056 \pm 0.004 for a sky cut of |b|>20^\circ (f_sky=0.66). Nonetheless, given that our method has different systematics than the more conventional method of observing the large scale B modes directly, it may be used as an important check in the case of a detection.
In this paper, we prove second derivative estimates together with classical solvability for the Dirichlet problem of certain Monge-Ampere type equations under sharp hypotheses. In particular we assume that the matrix function in the augmented Hessian is regular in the sense used by Trudinger and Wang in their study of global regularity in optimal transportation [28] as well as the existence of a smooth subsolution. The latter hypothesis replaces a barrier condition also used in their work. The applications to optimal transportation and prescribed Jacobian equations are also indicated.
We perform a systematic study of physical properties and distribution of neutral and ionised gas in the halo of the Milky Way (MW). Beside the large neutral intermediate- and high-velocity cloud (IVC, HVC) complexes there exists a population of partly ionised gaseous structures with low-column densities that have a substantial area filling factor. The origin and nature of these structures are still under debate. We analyse the physical parameters of the MW halo gas and the relation to quasar (QSO) metal-absorption line systems at low and high redshifts. For this purpose we combine new HI 21-cm data from the EBHIS and GASS surveys with optical quasar absorption line data to study the filling factor and distribution of these gaseous clouds in the halo at HI densities below 10^19 1/cm^2. This study is important to understand the evolution of the MW in particular and the gas accretion mechanisms of galaxies in general.
The ground state energy of the sinh-Gordon model defined on the strip is studied using the boundary thermodynamic Bethe ansatz equation. Its ultraviolet (small width of the strip) behavior is compared with the one obtained from the boundary Liouville reflection amplitude. The results are in perfect agreement in the allowable range of the parameters and provide convincing support for both approaches. We also describe how the ultraviolet limit of the effective central charge can exceed one in the parameter range when the Liouville zero mode forms a bound state.
Here we consider a metric-affine theory of gravity in which the gravitational Lagrangian is the scalar curvature. The matter action is allowed to depend also on the torsion and the nonmetricity, which are considered as the field variables together with the metric. We find the field equations of the theory and show that they reduce to Einstein equations in vacuum