Miracle-dz/UniFAR-FTUs huggingface dataset:
An Untriggered Search for Optical Bursts

We present an untriggered search for optical bursts with the Robotic Optical Transient Search Experiment (ROTSE-I) telephoto array. Observations were taken that monitor an effective 256 deg2 field continuously over 125 hr to mROTSE = 15.7. The uniquely large field, moderate limiting magnitude, and fast cadence of ~10 minutes permit transient searches in a new region of sensitivity. Our search reveals no candidate events. To quantify this result, we simulate potential optical bursts with peak magnitude mp at t = 10 s, which fade as f = , where αt < 0. Simple estimates based on observational evidence indicate that a search of this sensitivity begins to probe the possible region occupied by gamma-ray burst (GRB) orphan afterglows. Our observing protocol and image sensitivity result in a broad region of high detection efficiency for light curves to the bright and slowly varying side of a boundary running from [αt,mp] = [-2.0, 6.0] to [-0.3, 13.2]. Within this region, the integrated rate of brief optical bursts is less than 1.1 × 10-8 s-1 deg-2. At ~22 times the observed GRB rate from BATSE, this suggests a limit on θopt/θγ ≲ 5, where θopt and θγ are the optical and gamma-ray collimation angles, respectively. Several effects might explain the absence of optical bursts, and a search of the kind described here but more sensitive by about 4 mag should offer a more definitive probe.
A D-brane alternative to the MSSM

The success of SU(5)-like gauge coupling unification boundary conditions g32 = g22 = 5/3g12 has biased most attempts to embed the SM interactions into a unified structure. After discussing the limitations of the orthodox approach, we propose an alternative that appears to be quite naturally implied by recent developments based on D-brane physics. In this new alternative: 1) The gauge group, above a scale of order 1 TeV, is the minimal left-right symmetric extension SU(3) × SU(2)L × SU(2)R × U(1)B−L of the SM; 2) Quarks, leptons and Higgs fields come in three generations; 3) Couplings unify at an intermediate string scale Ms = 9 × 1011 GeV with boundary conditions g32 = gL2 = gR2 = 32/3 gB−L2. This corresponds to the natural embedding of gauge interactions into D-branes and is different from the standard SO(10) embedding which corresponds to kB−L = 8/3. Unification only works in the case of three generations; 4) Proton stability is automatic due to the presence of 2 discrete R-parity and lepton parities. A specific type-IIB string orientifold model with the above characteristics is constructed. The existence of three generations is directly related to the existence of three complex extra dimensions. In this model the string scale can be identified with the intermediate scale and SUSY is broken also at that scale due to the presence of anti-branes in the vacuum. We discuss a number of phenomenological issues in this model including Yukawa couplings and a built-in axion solution to the strong-CP problem. The present framework could be tested by future accelerators by finding the left-right symmetric extension of the SM at a scale of order 1 TeV.
Coexistence of antiferromagnetism and superconductivity in CeRhIn5 under high pressure and magnetic field

We report on detailed ac calorimetry measurements under high pressure and magnetic field of CeRhIn5. Under hydrostatic pressure the antiferromagnetic order vanishes near p_c*=2 GPa due to a first order transition. Superconductivity is found for pressures above 1.5 GPa inside the magnetic ordered phase. However, the superconductivity differ from the pure homogeneous superconducting ground state above 2 GPa. The application of an external magnetic field H || ab induces a transition inside the superconducting state above pc* which is strongly related to the re-entrance of the antiferromagnetism with field. This field-induced supplementary state vanishes above the quantum critical point in this system. The analogy to CeCoIn5 is discussed.
"Growing Evanescent Envelopes" and Anomalous Tunneling in Cascaded Sets of Frequency-Selective Surfaces in Their Stop Bands

Abstrac t: The presence of wave tunneling and the “growing evanescent envelope” for field distributions in suitably designed, periodically layered stacks of frequency selective surfaces (FSS) is discussed in this paper. It is known that a slab of double-negative (DNG) or left-handed metamaterial sandwiched between two vacuum half-spaces may lead to “growing” evanescent plane waves, which may be used to restore sub-wavelength information in Pendry’s “perfect” lens [ Phys. Rev. Lett. , 85, 3966, (2000)]. In this paper, it is shown that a completely different setup allows an analogous buildup of evanescently modulated waves. In particular, it is shown how an interface resonance phenomenon similar to the one present at the interface between metamaterials with oppositely signed constitutive parameters may be induced by a proper choice of the periodicities of the FSS stacks and the geometrical properties of these surfaces. The analysis is performed through an equivalent transmission-line approach, and some physical insights into this phenomenon are presented. Salient features, such as the complete wave tunneling through the pair of cascaded FSS, each operating at its bandgap, are presented and discussed.
The solar wind in time: a change in the behaviour of older winds?

In the present paper, we model the wind of solar analogues at different ages to investigate the evolution of the solar wind. Recently, it has been suggested that winds of solar type stars might undergo a change in properties at old ages, whereby stars older than the Sun would be less efficient in carrying away angular momentum than what was traditionally believed. Adding to this, recent observations suggest that old solar-type stars show a break in coronal properties, with a steeper decay in X-ray luminosities and temperatures at older ages. We use these X-ray observations to constrain the thermal acceleration of winds of solar analogues. Our sample is based on the stars from the `Sun in time' project with ages between 120-7000 Myr. The break in X-ray properties leads to a break in wind mass-loss rates ($\dot{M}$) at roughly 2 Gyr, with $\dot{M}$ (t 2 Gyr) $\propto$ $t^{-3.9}$. This steep decay in $\dot{M}$ at older ages could be the reason why older stars are less efficient at carrying away angular momentum, which would explain the anomalously rapid rotation observed in older stars. We also show that none of the stars in our sample would have winds dense enough to produce thermal emission above 1-2 GHz, explaining why their radio emissions have not yet been detected. Combining our models with dynamo evolution models for the magnetic field of the Earth we find that, at early ages ($\approx$100 Myr) our Earth had a magnetosphere that was 3 or more times smaller than its current size.
How Do Disks and Planetary Systems in High-mass Open Clusters Differ from Those around Field Stars?

Only star clusters that are sufficiently compact and massive survive largely unharmed beyond 10 . However, their compactness means a high stellar density, which can lead to strong gravitational interactions between the stars. As young stars are often initially surrounded by protoplanetary disks and later on potentially by planetary systems, the question arises to what degree these strong gravitational interactions influence planet formation and the properties of planetary systems. Here, we perform simulations of the evolution of compact high-mass clusters like Trumpler 14 and Westerlund 2 from the embedded to the gas-free phase and study the influence of stellar interactions. We concentrate on the development of the mean disk size in these environments. Our simulations show that in high-mass open clusters 80%–90% of all disks/planetary systems should be smaller than 50 just as a result of the strong stellar interactions in these environments. Already in the initial phases, three to four close flybys lead to typical disk sizes within the range of 18–27 . Afterward, the disk sizes are altered only to a small extent. Our findings agree with the recent observation that the disk sizes in the once dense environment of the Upper Scorpio OB association, NGC 2362, and h/χPersei are at least three times smaller in size than, for example, in Taurus. We conclude that the observed planetary systems in high-mass open clusters should also be on average smaller than those found around field stars; in particular, planets on wide orbits are expected to be extremely rare in such environments.
Study of plasmonic slot waveguides with a nonlinear metamaterial core: semi-analytical and numerical methods

Two distinct models are developed to investigate the transverse magnetic stationary solutions propagating in one-dimensional anisotropic nonlinear plasmonic structures made from a Kerr-type nonlinear metamaterial core embedded between two semi-infinite metal claddings. The first model is semi-analytical, in which we assume that the anisotropic nonlinearity depends only on the transverse component of the electric field and that the nonlinear refractive index modification is small compared to the linear one. This method allows us to derive analytically the field profiles and nonlinear dispersion relations in terms of the Jacobi elliptical functions. The second model is fully numerical and is based on the finite element method in which all the components of the electric field are considered in the Kerr-type nonlinearity, with no presumptions as to the nonlinear refractive index change. Our finite-element-based model is valid beyond the weak nonlinearity regime and generalizes the well-known single-component fixed power algorithm that is usually used. Examples of the main cases are investigated, including those with strong spatial nonlinear effects at low power. Loss issues are reduced through the use of a gain medium in the nonlinear metamaterial core. Using anisotropic nonlinear FDTD simulations, we provide some results for the properties of the main solution.
Global Core Plasma Model

The global core plasma model (GCPM) provides empirically derived core plasma density as a function of geomagnetic and solar conditions throughout the inner magnetosphere. It is continuous in value and gradient and is composed of separate models for the ionosphere, plasmasphere, plasmapause, trough, and polar cap. The relative composition of plasmaspheric H+, He+, and O+ is included in the GCPM. A blunt plasmaspheric bulge and rotation of the bulge with changing geomagnetic conditions is included. The GCPM is an amalgam of density models intended to serve as a framework for continued improvement as new measurements become available and are used to characterize core plasma density, composition, and temperature.
Model-independent reconstruction of the linear anisotropic stress η

In this work, we use recent data on the Hubble expansion rate H(z), the quantity fσ8(z) from redshift space distortions and the statistic Eg from clustering and lensing observables to constrain in a model-independent way the linear anisotropic stress parameter η. This estimate is free of assumptions about initial conditions, bias, the abundance of dark matter and the background expansion. We denote this observable estimator as ηobs. If ηobs turns out to be different from unity, it would imply either a modification of gravity or a non-perfect fluid form of dark energy clustering at sub-horizon scales. Using three different methods to reconstruct the underlying model from data, we report the value of ηobs at three redshift values, z=0.29, 0.58, 0.86. Using the method of polynomial regression, we find ηobs=0.57±1.05, ηobs=0.48±0.96, and ηobs=−0.11±3.21, respectively. Assuming a constant ηobs in this range, we find ηobs=0.49±0.69. We consider this method as our fiducial result, for reasons clarified in the text. The other two methods give for a constant anisotropic stress ηobs=0.15±0.27 (binning) and ηobs=0.53 ± 0.19 (Gaussian Process). We find that all three estimates are compatible with each other within their 1σ error bars. While the polynomial regression method is compatible with standard gravity, the other two methods are in tension with it.
Particle Creation in the Effective Action Method

Abstract The effect of particle creation by nonstationary external fields is considered as a radiation effect in the expectation-value spacetime. The energy of created massless particles is calculated as the vacuum contribution in the energy-momentum tensor of the expectation value of the metric. The calculation is carried out for an arbitrary quantum field coupled to all external fields entering the general second-order equation. The result is obtained as a functional of the external fields. The paper gives a systematic derivation of this result on the basis of the nonlocal effective action. Although the derivation is quite involved and touches on many aspects of the theory, the result itself is remarkably simple. It brings the quantum problem of particle creation to the level of complexity of the classical radiation problem. For external fields like the electromagnetic or gravitational field there appears a quantity, the radiation moment, that governs both the classical radiation of waves and the quantum particle production. The vacuum radiation of an electrically charged source is considered as an example. The research is aimed at the problem of backreaction of the vacuum radiation.
Random Levy Matrices Revisited

We compare eigenvalue densities of Wigner random matrices whose elements are independent identically distributed (iid) random numbers with a L´evy distribution and maximally random matrices with a rotationally invariant measure exhibiting a power law spectrum given by stable laws of free random variables. We compute the eigenvalue density of Wigner-L´evy (WL) matrices using (and correcting) the method by Bouchaud and Cizeau (BC), and of free random L´evy (FRL) rotationally invariant matrices by adapting results of free probability calculus. We compare the two types of eigenvalue spectra. Both ensembles are spectrally stable with respect to the matrix addition. The discussed ensemble of FRL matrices is maximally random in the sense that it maximizes Shannon’s entropy. We ﬁnd a perfect agreement between the numerically sampled spectra and the analytical results already for matrices of dimension N = 100. The numerical spectra show very weak dependence on the matrix size N as can be noticed by comparing spectra for N = 400. After a pertinent rescaling spectra of Wigner-L´evy matrices and of symmetric FRL matrices have the same tail behavior. As we discuss towards the end of the paper the correlations of large eigenvalues in the two ensembles are however diﬀerent. We illustrate the relation between the two types of stability and show that the addition of many randomly rotated Wigner-L´evy matrices leads by a matrix central limit theorem to FRL spectra, providing an explicit realization of the maximal randomness principle.
Kronig-Penney-Ising picture of colossal magnetoresistance

From general arguments, it is shown that a magnetic Kronig-Penney model based on the thermodynamics of an Ising model can be used for describing the Colossal Magnetoresistance (CMR) phenomenon. The model considers a tunneling-like transmission process of hopping electrons through a dynamic lattice characterized by evolving magnetic clusters. In this model, correlations between the magnetic states are considered to be more relevant than the lattice strain effects for obtaining the CMR features. Physical arguments lead to the theoretical description of the intrinsic temperature and field dependences of the CMR observed in typical manganite materials.
Atomic diffusion from a material surface into a grain boundary

A model problem of stress–induced atomic diffusion from the surface of a material into a semi–infinite grain boundary orthogonal to the surface is analysed. The governing equation is shown to be a singular integro–differential equation. An algorithm for an exact solution to this problem is proposed. It involves reduction to a functional–difference equation in a strip and then to a Riemann–Hilbert boundary–value problem for an open contour that admits solution by quadratures. Analytical continuation of the solution of the difference equation in the strip is constructed. The continuation is a meromorphic function in the exterior of the strip. Its poles form a countable set and are not periodic. In addition to a closed–form solution of the integro–differential equation, a procedure for finding a rapidly convergent series representation and an asymptotic expansion for large arguments are proposed. Asymptotic analysis and numerical results for the grain–boundary traction, the atomic flux in the boundary and the displacement rate are reported and discussed.
GRB 990123: The Optical Flash and the Fireball Model

We show that the ongoing observations of the remarkable burst GRB 990123 agree with the predictions of the fireball model. Specifically, the observations confirm the recent prediction that the reverse shock propagating into the ejecta would produce a very strong prompt optical flash. This reverse shock has also produced the 8.46 GHz radio signal, observed after 1 day. The forward shock, which is the origin of the classical afterglow, has produced the prompt X-ray signal as well as the late optical and IR emission. The observations suggest that the initial Lorentz factor of the ejecta was ~200. Within factors of order unity, this crude model explains all current observations of GRB 990123.
Emergent universe in theories with natural UV cutoffs

We investigate the realization of the emergent universe scenario in theories with natural UV cutoffs, namely a minimum length and a maximum momentum, quantified by a new deformation parameter in the generalized uncertainty principle. We extract the Einstein static universe solutions and we examine their stability through a phase-space analysis. As we show, the role of the new deformation parameter is crucial in a twofold way: firstly, it leads to the appearance of new Einstein static universe critical points, that are absent in standard cosmology. Secondly, it provides a way for a graceful exit from the Einstein static universe into the expanding thermal history, that is needed for a complete and successful realization of the emergent universe scenario.
Microstructure dependence of low-temperature elastic properties in amorphous diamondlike carbon films

We have studied the internal friction and the relative change in the speed of sound of amorphous diamond-like carbon films prepared by pulsed-laser deposition from 0.3 K to room temperature. Like the most of amorphous solids, the internal friction below 10 K exhibits a temperature independent plateau. The values of the internal friction plateau, however, are slightly below the universal ``glassy range'' where the internal frictions of almost all amorphous solids lie. Similar observations have been made in our earlier studies in the thin films of amorphous silicon and amorphous germanium, and the behavior could be well accounted for by the existence of the low-energy atomic tunneling states. In this work, we have varied the concentration of sp^3 versus sp^2 carbon atoms by increasing laser fluence from 1.5 to 30 J/cm^2. Our results show that both the internal friction and the speed of sound have a nonmonotonic dependence on sp^3/sp^2 ratio with the values of the internal friction plateau varying between 6x10^-5 and 1.1x10^-4. We explain our findings as a result of a possible competition between the increase of atomic bonding and the increase of internal strain in the films, both of which are important in determining the tunneling states in amorphous solids. In contrast, no significant dependence of laser fluence is found in shear moduli of the films, which vary between 220 and 250 GPa. The temperature dependence of the relative change in speed of sound, although it shows a similar nonmonotonic dependence on laser fluence as the internal friction, differs from those found in thin films of amorphous silicon and amorphous germanium, which we explain as having the same origin as the anomalous behavior recently observed in the speed of sound of thin nanocrystalline diamond films.
GRAPES, Grism Spectroscopy of the Hubble Ultra Deep Field: Description and Data Reduction

We present deep unbiased spectroscopy of the Hubble Ultra Deep Field (UDF) carried out using the slitless grism spectroscopy mode of the Advanced Camera for Surveys on the Hubble Space Telescope (HST). The Grism ACS Program for Extragalactic Science (GRAPES) achieves continuum detection as faint as zAB = 27.2 using 40 orbits (9.2 × 104 s) on HST. The data were taken at four orientation angles to correct for the overlap of spectra. GRAPES data provide a unique, uninterrupted, low-resolution (R = 100) spectral coverage for 5500 Å < λ < 10500 Å and allow us to detect high-redshift galaxies at 4 < z < 7 whether they have Lyα lines or just show the Lyman break, as well as find low-luminosity active galactic nuclei in an unbiased fashion. This paper describes in detail the observations and the data reduction and examines the quality of the extracted spectra. Subsequent papers will deal with the analysis of the data. The extracted and calibrated GRAPES spectra will be available from MAST at STScI.
The Cyclotron Fundamental Exposed in the High-Field Magnetic Variable V884 Herculis

High-quality phase-resolved optical spectropolarimetry is presented for the magnetic cataclysmic variable V884 Her. The overall circular polarization during active accretion states is low and only slightly variable in the range 5000-8000 Å. However, the polarization is highly structured with wavelength, showing very broad polarization humps, narrow features that are associated with weak absorption lines in the total spectral flux, and sharp reversals across each major emission line. The polarization reversals arise from Zeeman splitting in the funnel gas in a longitudinal magnetic field B ~ 30 kG. The set of narrow, polarized absorption features matches the Zeeman pattern of hydrogen for a nearly uniform magnetic field of B = 150 MG, indicating that the features are "halo" absorption lines formed in a relatively cool reversing layer above the shock. With this identification, the broad polarization humps centered near 7150 Å and below 4000 Å are assigned to cyclotron emission from the fundamental and first harmonic (n = 2), respectively. V884 Her is only the second AM Her system known with a field exceeding 100 MG and the first case in which the cyclotron fundamental has been directly observed from a magnetic white dwarf.
Transit‐time mechanism of plasma instability in high electron mobility transistors

We show that the transit‐time effects in the high‐electric‐field region near the drain edge of the channel of a field effect transistor can increase the increment of plasma wave growth in the device channel. These electron transit‐time effects might lead to the plasma wave instability in high‐electron‐mobility transistors (HEMTs) in the terahertz range of frequencies. We demonstrate that the self‐excitation of plasma oscillations is possible when the ratio of the electron velocity in the high field region, ud, and the gate length, Lg, is sufficiently large in comparison with the electron collision frequency in the gated channel, ν, i.e udLg > ν/k, where k is a constant. Hence, in contrast with the Dyakonov–Shur mechanism of plasma instability in HEMTs, the plasma instability associated with the mechanism under consideration can occur at fairly low values of the electron mobility in the gated portion of the HEMT channel. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)