ShantanuT01/DACTYL-Pretraining huggingface dataset:
If the Higgs boson indeed weighs about 114 to 115 GeV, there must be new physics beyond the Standard Model at some scale \la 10^6 GeV. The most plausible new physics is supersymmetry, which predicts a Higgs boson weighing \la 130 GeV. In the CMSSM with R and CP conservation, the existence, production and detection of a 114 or 115 GeV Higgs boson is possible if \tan\beta \ga 3. However, for the radiatively-corrected Higgs mass to be this large, sparticles should be relatively heavy: m_{1/2} \ga 250 GeV, probably not detectable at the Tevatron collider and perhaps not at a low-energy e^+ e^- linear collider. In much of the remaining CMSSM parameter space, neutralino-stau coannihilation is important for calculating the relic neutralino density, and we explore implications for the elastic neutralino-nucleon scattering cross section.
Here, we report the unusual behaviour shown by the (BiFeO3)1-x-(PbTiO3)x (BF-xPT) films prepared using a multilayer deposition approach by chemical solution deposition method. Thin film samples of various compositions were prepared by depositing several bilayers of BF and PT precursors by varying the BF or PT layer thicknesses. X-ray diffraction showed that final samples of all compositions show mixing of the two compounds resulting in a single phase mixture, also confirmed by transmission electron microscopy. In contrast to bulk equilibrium compositions, our samples show a monoclinic (MA type) structure suggesting disappearance of morphotropic phase boundary (MPB) about x = 0.30 as observed in the bulk. This is accompanied by the lack of any enhancement of remnant polarization at MPB as shown by the ferroelectric measurements. Magnetic measurements show that the magnetization of the samples increases with increasing BF content. Significant magnetization of the samples indicates melting of spin spirals in the BF-xPT arising from random distribution of iron atoms across the film. Absence of Fe2+ ions in the films was corroborated by X-ray photoelectron spectroscopy measurements. The results illustrate that used thin film processing methodology significantly changes the structural evolution in contrast to predictions from the equilibrium phase diagram as well as modify the functional characteristics of BP-xPT system dramatically.
We show that the energy splitting between the bonding and antibonding molecular states of holes in vertically stacked quantum dots can be tuned using longitudinal magnetic fields. With increasing field, the energy splitting first decreases down to zero and then to negative values, which implies a bonding-to-antibonding ground state transition. This effect is a consequence of the enhancement of the valence band spin-orbit interaction induced by the magnetic field, and it provides a flexible mechanism to switch the molecular ground state from bonding to antibonding.
We investigate the magnetic phase diagram of the two-dimensional model for e_g electrons which describes layered nickelates. One finds a generic tendency towards magnetic order accompanied by orbital polarization. For two equivalent orbitals with diagonal hopping such orbitally polarized phases are induced by finite crystal field.
This is a series of remedial lectures on open and unoriented strings for the heterotic string generation. The particular focus is on the interesting features that arise under T-duality---D-branes and orientifolds. The final lecture discusses the application to string duality. There will be no puns. Lectures presented by J. P. at the ITP from Nov. 16 to Dec. 5, 1995. References updated through Jan. 25, 1996.
The evolution of the magnetic field of an accreting magnetic white dwarf with an initially dipolar field at the surface has been studied for non-spherical accretion under simplifying assumptions. Accretion on to the polar regions tends to advect the field toward the stellar equator which is then buried. This tendency is countered by Ohmic diffusion and magneto-hydrodynamic instabilities. It is argued that if matter is accreted at a rate of $\dot{M}_{\rm crit} \sim 10^{16}$ g s$^{-1}$ and the total mass accreted exceeds a critical value $\Delta M_{\rm crit} \sim 0.1-0.2\ms$, the field may be expected to be restructured, and the polar field to be reduced} reaching a minimum value of $\sim 10^3$ G (the "bottom field") independently of the initial field strength. Below this critical accretion rate, the field diffuses faster than it can be advected, and accretion has little effect on field strength and structure.
We present the results of a search for rapidly evolving transients in the Dark Energy Survey Supernova Programme. These events are characterized by fast light curve evolution (rise to peak in $\lesssim 10$ d and exponential decline in $\lesssim30$ d after peak). We discovered 72 events, including 37 transients with a spectroscopic redshift from host galaxy spectral features. The 37 events increase the total number of rapid optical transients by more than factor of two. They are found at a wide range of redshifts ($0.05<z<1.56$) and peak brightnesses ($-15.75>M_\mathrm{g}>-22.25$). The multiband photometry is well fit by a blackbody up to few weeks after peak. The events appear to be hot ($T\approx10000-30000$ K) and large ($R\approx 10^{14}-2\cdot10^{15}$ cm) at peak, and generally expand and cool in time, though some events show evidence for a receding photosphere with roughly constant temperature. Spectra taken around peak are dominated by a blue featureless continuum consistent with hot, optically thick ejecta. We compare our events with a previously suggested physical scenario involving shock breakout in an optically thick wind surrounding a core-collapse supernova (CCSNe), we conclude that current models for such a scenario might need an additional power source to describe the exponential decline. We find these transients tend to favor star-forming host galaxies, which could be consistent with a core-collapse origin. However, more detailed modeling of the light curves is necessary to determine their physical origin.
We present a comparative study of the fate of an Ising ferromagnet on the square lattice with periodic boundary conditions evolving under three different zero-temperature dynamics. The first one is Glauber dynamics, the two other dynamics correspond to two limits of the directed Ising model, defined by rules that break the full symmetry of the former, yet sharing the same Boltzmann-Gibbs distribution at stationarity. In one of these limits the directed Ising model is reversible, in the other one it is irreversible. For the kinetic Ising-Glauber model, several recent studies have demonstrated the role of critical percolation to predict the probabilities for the system to reach the ground state or to fall in a metastable state. We investigate to what extent the predictions coming from critical percolation still apply to the two other dynamics.
Counting pattern avoiding ballot paths begins with a careful analysis of the pattern. Not the length, but the characteristics of the pattern are responsible for the difficulties in finding explicit solutions. Certain features, like overlap and difference in number of right and up steps determine the solution of the recursion formula. If the recursion can be solved by a polynomial sequence, we apply the Finite Operator Calculus to find an explicit form of the solution in terms of binomial coefficients. Keywords: Pattern avoidance, ballot path, Dyck path, Finite Operator Calculus, Umbral Calculus
The moduli space $\mathscr{M}$ of surfaces of general type with $p_g=q=1, K^2=g=3$ (where $g$ is the genus of the Albanese fibration) was constructed by Catanese and Ciliberto in \cite{CaCi93}. In this paper we characterize the subvariety $\mathscr{M}_2 \subset \mathscr{M}$ corresponding to surfaces containing a genus 2 pencil, and moreover we show that there exists a non-empty, dense subset $\mathscr{M}^0 \subset \mathscr{M}$ which parametrizes isomorphism classes of surfaces with birational bicanonical map.
The mass function of galaxy clusters is an important cosmological probe. Differences in the selection method could potentially lead to biases when determining the mass function. From the optical and X-ray data of the XMM-Newton Follow-Up Survey, we obtained a sample of galaxy cluster candidates using weak gravitational lensing, the optical Postman matched filter method, and a search for extended X-ray sources. We developed our weak-lensing search criteria by testing the performance of the aperture mass statistic on realistic ray-tracing simulations matching our survey parameters and by comparing two filter functions. We find that the dominant noise source for our survey is shape noise at almost all significance levels and that spurious cluster detections due to projections of large-scale structures are negligible, except possibly for highly significantly detected peaks. Our full cluster catalog has 155 cluster candidates, 116 found with the Postman matched filter, 59 extended X-ray sources, and 31 shear selected potential clusters. Most of these cluster candidates were not previously known. The present catalog will be a solid foundation for studying possible selection effects in either method.
There have been a few reports in the literature of counter-Evershed flows observed in well developed sunspot penumbrae, i.e. flows directed towards the umbra along penumbral filaments. Here we investigate the driving forces of such counter-Evershed flows in a radiative magnetohydrodynamic simulation of a sunspot and compare them with the forces acting on the normal Evershed flow. The simulation covers a timespan of 100 solar hours and generates an Evershed outflow exceeding 8 km s$^{-1}$ in the penumbra along radially aligned filaments where the magnetic field is almost horizontal. Additionally, the simulation produces a fast counter-Evershed flow (i.e., an inflow near $\tau = 1$) in some regions within the penumbra, reaching peak flow speeds of $\sim$12 km s$^{-1}$. The counter-Evershed flows are transient and typically last a few hours before they turn into outflows again. By using the kinetic energy equation and evaluating its various terms in the simulation box, we found that the Evershed flow occurs due to overturning convection in a strongly inclined magnetic field while the counter-Evershed flows can be well described as siphon flows.
The subject of this paper is a generalized Camassa-Holm equation under random perturbation. We first establish local existence and uniqueness results as well as blow-up criteria for pathwise solutions in the Sobolev spaces $H^s$ with $s>3/2$. Then we analyze how noise affects the dependence of solutions on initial data. Even though the noise has some already known regularization effects, much less is known concerning the dependence on initial data. As a new concept we introduce the notion of stability of exiting times and construct an example showing that multiplicative noise (in It\^{o} sense) cannot improve the stability of the exiting time, and simultaneously improve the continuity of the dependence on initial data. Finally, we obtain global existence theorems and estimate associated probabilities.
We consider the solution of the equation of motion of a classical/quantum spin subject to a monochromatical, elliptically polarized external field. The classical Rabi problem can be reduced to third order differential equations with polynomial coefficients and hence solved in terms of power series in close analogy to the confluent Heun equation occurring for linear polarization. Application of Floquet theory yields the physically interesting quasienergy as a function of the parameters of the problem and expressions for the Bloch-Siegert shift of resonance frequencies. Various limit cases cases have been thoroughly investigated.
Three binaries are now established sources of emission at very high energies (>1e11 eV). They are composed of a massive star and a compact object. The emission can be due to the interaction of the relativistic wind from a young ms pulsar with the stellar wind of the companion, by which rotation-power ends up as non-thermal flux. Variations at VHE energies are explained as due to gamma-gamma absorption and/or changes in shock location along the orbit. Resolved radio emission is due to cooling particles trailing the pulsar.
Sparse voxel-based 3D convolutional neural networks (CNNs) are widely used for various 3D vision tasks. Sparse voxel-based 3D CNNs create sparse non-empty voxels from the 3D input and perform 3D convolution operations on them only. We propose a simple yet effective padding scheme --- interpolation-aware padding to pad a few empty voxels adjacent to the non-empty voxels and involve them in the 3D CNN computation so that all neighboring voxels exist when computing point-wise features via the trilinear interpolation. For fine-grained 3D vision tasks where point-wise features are essential, like semantic segmentation and 3D detection, our network achieves higher prediction accuracy than the existing networks using the nearest neighbor interpolation or the normalized trilinear interpolation with the zero-padding or the octree-padding scheme. Through extensive comparisons on various 3D segmentation and detection tasks, we demonstrate the superiority of 3D sparse CNNs with our padding scheme in conjunction with feature interpolation.
The magnetic and optical properties of titanium dichalcogenide compounds, TiX$_2$ (X = S, Se and Te) have been calculated by first principles calculations using density functional theory (DFT) as implemented in SIESTA code. A 3x3 supercell of the compounds is taken in this study to be able to tune the properties obtained from the unit cell of these compounds. With magnetic states (ferromagnetic nature) as the attained ground state, spin polarized calculations are performed to obtain the mentioned properties. Further, with spin polarization into effect, external electric field (along z-direction) and biaxial strain (along x and y-directions) is employed to study their effect on these properties. The effect of biaxial strain on the geometry of the compounds is also studied. It is observed that the pristine supercell of the compounds possess a good amount of magnetic moment and this can be modulated using the applied field and strain. For the optical properties, polarized light along the z-direction (c axis) is used. These properties include the calculation of real & imaginary parts of dielectric function, absorption coefficient, reflectance, optical conductivity and refractive index in 0-25 eV energy range. Various modulations of these properties are observed including the blue-shifts and red-shifts of energies with highest peaks in the visible region and also shifting of energies to other regions of the electromagnetic spectrum. Hence, with the tunable magnetic and diverse optical properties, the compounds can be useful in the field of spintronics and in making various optical devices.
The discovery of relativistic jets and superluminal sources associated with accreting X-ray binaries in the Galaxy opened new ways of investigating the physics of outflows from compact objects. The short timescales and relatively large angular sizes of Galactic jets allow to probe the physics of relativistic outflows to unprecedented details. In this article I discuss results of recent modelling of Galactic jets, covering both radiative and dynamical aspects, which can shed light on different features of their extragalactic cousins.
The origins of the stellar-mass black hole mergers discovered by LIGO/Virgo are still unknown. Here we show that, if migration traps develop in the \add{accretion} disks of Active Galactic Nuclei (AGNs) and promote the mergers of their captive black holes, the majority of black holes within disks will undergo hierarchical mergers---with one of the black holes being the remnant of a previous merger. 40% of AGN-assisted mergers detected by LIGO/Virgo will include a black hole with mass $\gtrsim 50$ M$_\odot$, the mass limit from stellar core collapse. Hierarchical mergers at traps in AGNs will exhibit black hole spins (anti-)aligned with the binary's orbital axis, a distinct property from other hierarchical channels. Our results are suggestive, although not definitive (with Odds ratio of $\sim 1$), that LIGO's heaviest merger so far, GW170729, could have originated from this channel.
A review on current theories and observations of high-mass star formation is given. Particularly the influence of magnetic fields and feedback mechanisms, and of varying initial conditions on theories are discussed. The, in my biased view, most important observations to put strong constraints on models of high-mass star formation are pres ented, in particular bearing on the existence and properties of high-mass starless cores, the role of filaments in the mass transport to high-mass cores, and the propertie s of disks around high-mass stars.
An analogue of Talagrand's convex distance for binomial and Poisson point processes is defined. A corresponding large deviation inequality is proved.
We present stellar dynamical models of the lopsided, double-peaked nucleus of M31, derived from Hubble Space Telescope (HST) photometry. A Schwarzscild-type method, in conjunction with Richardson-Lucy deconvolution, was employed to construct steadily rotating, hot, stellar disks. The stars orbit a massive dark object, on prograde and retrograde quasi-periodic loop orbits. Our results support Tremaine's eccentric disk model, extended to include a more massive disk, non zero pattern speed ($\Omega$), and different viewing angle. Most of the disk mass populated prograde orbits, with $\simeq 3.4%$ on retrograde orbits. The best fits to photometric and kinematic maps were disks with $\Omega\approx 16\kmspc $. We speculate on the origins of the lopsidedness, invoking recent work on the linear overstability of nearly Keplerian disks, that possess even a small amount of a counter-rotating component. Accretion of material-no more massive than a globular cluster-onto a preexisting stellar disk, will account for the mass in our retrograde orbits, and could have stimulated the lopsidedness seen in the nucleus of M31.
We propose a scenario for the formation of DA white dwarfs with very thin helium buffers. For these stars we explore the possible occurrence of diffusion-induced CNO- flashes, during their early cooling stage. In order to obtain very thin helium buffers, we simulate the formation of low mass remnants through an AGB final/late thermal pulse (AFTP/LTP scenario). Then we calculate the consequent white dwarf cooling evolution by means of a consistent treatment of element diffusion and nuclear burning. Based on physically sounding white dwarf models, we find that the range of helium buffer masses for these diffusion-induced novas to occur is significantly smaller than that predicted by the only previous study of this scenario. As a matter of fact, we find that these flashes do occur only in some low-mass (M < 0.6M) and low metallicity (Z_ZAMS <0.001) remnants about 10^6 - 10^7 yr after departing from the AGB. For these objects, we expect the luminosity to increase by about 4 orders of magnitude in less than a decade. We also show that diffusion-induced novas should display a very typical eruption lightcurve, with an increase of about a few magnitudes per year before reaching a maximum of M_V ~ -5 to -6. Our simulations show that surface abundances after the outburst are characterized by logNH/NHe ~ -0.15...0.6 and N>C>O by mass fractions. Contrary to previous speculations we show that these events are not recurrent and do not change substantially the final H-content of the cool (DA) white dwarf. (Abridged)
We describe the effect of rational singularities on the Brauer group of a surface, and compute the Brauer groups of all singular del Pezzo surfaces over an algebraically closed field.
It is shown that the gravitational field, as a physical field developing in the Minkowsky space, does not lead to unlimited gravitational collapse of massive bodies and, hence, excludes a possibility of the formation of the ``black holes''.
A model is presented for the quantum transport of electrons, across finite atomic wire nanojunctions between electric leads, at zero bias limit. In order to derive the appropriate transmission and reflection spectra, familiar in the Landauer-B\"{u}ttiker formalism, we develop the algebraic phase field matching theory (PFMT). In particular, we apply our model calculations to determine the electronic conductance for freely suspended monatomic linear sodium wires (MLNaW) between leads of the same element, and for the diatomic copper-cobalt wires (DLCuCoW) between copper leads on a Cu(111) substrate. Calculations for the MLNaW system confirm the correctness and functionality of our PFMT approach. We present novel transmission spectra for this system, and show that its transport properties exhibit the conductance oscillations for the odd- and even-number wires in agreement with previously reported first-principle results. The numerical calculations for the DLCuCoW wire nanojunctions are motivated by the stability of these systems at low temperatures. Our results for the transmission spectra yield for this system, at its Fermi energy, a monotonic exponential decay of the conductance with increasing wire length of the Cu-Co pairs. This is a cumulative effect which is discussed in detail in the present work, and may prove useful for applications in nanocircuits. Furthermore, our PFMT formalism can be considered as a compact and efficient tool for the study of the electronic quantum transport for a wide range of nanomaterial wire systems. It provides a trade-off in computational efficiency and predictive capability as compared to slower first-principle based methods, and has the potential to treat the conductance properties of more complex molecular nanojunctions.
We establish the existence and symmetry of all minimizers of a constrained variational problem involving the fractional gradient. This problem is closely connected to some fractional kinetic equations.
After a summary of the motivations for searching flavour violating decays and electric dipole moments in the leptonic sector, I briefly sketch the present status of the limits on lepton-slepton misalignement and discuss the potentialities of the planned experimental improvements. Candidates for theories beyond the Standard Model have to satisfy all these experimental constraints; I will discuss in particular how the supersymmetric SM extended with the see-saw faces the flavour problem.
We present time-resolved spectroscopy and photometry of the dwarf nova SBSS 1108+574, obtained during the 2012 outburst. Its quiescent spectrum is unusually rich in helium, showing broad, double-peaked emission lines from the accretion disc. We measure a line flux ratio HeI 5875/Halpha = 0.81 +/- 0.04, a much higher ratio than typically observed in cataclysmic variables (CVs). The outburst spectrum shows hydrogen and helium in absorption, with weak emission of Halpha and HeI 6678, as well as strong HeII emission.   From our photometry, we find the superhump period to be 56.34 +/- 0.18 minutes, in agreement with the previously published result. The spectroscopic period, derived from the radial velocities of the emission lines, is found to be 55.3 +/- 0.8 minutes, consistent with a previously identified photometric orbital period, and significantly below the normal CV period minimum. This indicates that the donor in SBSS 1108+574 is highly evolved. The superhump excess derived from our photometry implies a mass ratio of q = 0.086 +/- 0.014. Our spectroscopy reveals a grazing eclipse of the large outbursting disc. As the disc is significantly larger during outburst, it is unlikely that an eclipse will be detectable in quiescence. The relatively high accretion rate implied by the detection of outbursts, together with the large mass ratio, suggests that SBSS 1108+574 is still evolving towards its period minimum.