ShantanuT01/DACTYL-Pretraining huggingface dataset:
We study the effects of strong coupling of a localized state charge to one-dimensional electronic channels out of equilibrium. While the state of this charge and the coupling strengths determine the scattering phase shifts in the channels, the nonequilibrium partitioning noise induces the tunneling transitions to the localized state. The strong coupling leads to a nonperturbative backaction effect which is manifested in the orthogonality catastrophe and the Fermi-edge singularity in the transition rates. We predict an unusually pronounced manifestation of the non-Gaussian component of noise that breaks the charge symmetry, resulting in a nontrivial shape, and a shift of the position of the tunneling resonance.
We theoretically investigate dynamics of antiferromagnetic domain walls driven by spin-orbit torques in antiferromagnet/heavy metal bilayers. We show that spin-orbit torques drive antiferromagnetic domain walls much faster than ferromagnetic domain walls. As the domain wall velocity approaches the maximum spin-wave group velocity, the domain wall undergoes Lorentz contraction and emits spin-waves in the terahertz frequency range. The interplay between spin orbit torques and the relativistic dynamics of antiferromagnetic domain walls leads to the efficient manipulation of antiferromagnetic spin textures and paves the way for the generation of high frequency signals in antiferromagnets.
This work considers a generalization of Grover's search problem, viz., to find any one element in a set of acceptable choices which constitute a fraction f of the total number of choices in an unsorted data base. An infinite family of sure-success quantum algorithms are introduced here to solve this problem, each member for a different range of f. The nth member of this family involves n queries of the data base, and so the lowest few members of this family should be very convenient algorithms within their ranges of validity. The even member {A}_{2n} of the family covers ever larger range of f for larger n, which is expected to become the full range 0 <= f <= 1 in the limit n -->infinity.
We derive a simple bijection between geometric plane perfect matchings on $2n$ points in convex position and triangulations on $n+2$ points in convex position. We then extend this bijection to monochromatic plane perfect matchings on periodically $k$-colored vertices and $(k+2)$-gonal tilings of convex point sets. These structures are related to a generalization of Temperley-Lieb algebras and our bijections provide explicit one-to-one relations between matchings and tilings. Moreover, for a given element of one class, the corresponding element of the other class can be computed in linear time.
We perform 1D calculations of neutrino opacities inside a young "strange star" assumed to be the result of the conversion process of a normal neutron object. We evaluate the deleptonization and cooling timescales, which happen to be longer than the proto-NS analogues, and preliminary address the features of the emerging neutrino signal.
In this paper, we consider maximum possible value for the sum of cardinalities of hyperedges of a hypergraph without a Berge $4$-cycle. We significantly improve the previous upper bound provided by Gerbner and Palmer. Furthermore, we provide a construction that slightly improves the previous lower bound.
We construct phenomenologically viable models of lepton masses and mixing based on modular $A_4$ invariance broken to residual symmetries $\mathbb{Z}^{T}_3$ or $\mathbb{Z}^{ST}_3$ and $\mathbb{Z}^S_2$ respectively in the charged lepton and neutrino sectors. In these models the neutrino mixing matrix is of trimaximal mixing form. In addition to successfully describing the charged lepton masses, neutrino mass-squared differences and the atmospheric and reactor neutrino mixing angles $\theta_{23}$ and $\theta_{13}$, these models predict the values of the lightest neutrino mass (i.e., the absolute neutrino mass scale), of the Dirac and Majorana CP violation(CPV) phases, as well as the existence of specific correlations between i) the values of the solar neutrino mixing angle $\theta_{12}$ and the angle $\theta_{13}$ (which determines $\theta_{12}$), ii) the values of the Dirac CPV phase $\delta$ and of the angles $\theta_{23}$ and $\theta_{13}$, iii) the sum of the neutrino masses and $\theta_{23}$, and iv) between the two Majorana phases.
Wood et al suggested that mass-loss rate is a function of X-ray flux ($\dot{M} \propto F_x^{1.34}$) for dwarf stars with $F_x \lesssim F_{x,6} \equiv 10^6$ erg cm$^{-2}$ s$^{-1}$. However, more active stars do not obey this relation. These authors suggested that the break at $F_{x,6}$ could be caused by significant changes in magnetic field topology that would inhibit stellar wind generation. Here, we investigate this hypothesis by analysing the stars in Wood et al's sample that had their surface magnetic fields reconstructed through Zeeman-Doppler Imaging (ZDI). Although the solar-like outliers in the $\dot{M}$ -- $F_x$ relation have higher fractional toroidal magnetic energy, we do not find evidence of a sharp transition in magnetic topology at $F_{x,6}$. To confirm this, further wind measurements and ZDI observations at both sides of the break are required. As active stars can jump between states with highly toroidal to highly poloidal fields, we expect significant scatter in magnetic field topology to exist for stars with $F_x \gtrsim F_{x,6}$. This strengthens the importance of multi-epoch ZDI observations. Finally, we show that there is a correlation between $F_x$ and magnetic energy, which implies that $\dot{M}$ -- magnetic energy relation has the same qualitative behaviour as the original $\dot{M}$ -- $F_x$ relation. No break is seen in any of the $F_x$ -- magnetic energy
The angular motion of a few-body system is described with global vectors which depend on the positions of the particles. The previous study using a single global vector is extended to make it possible to describe both natural and unnatural parity states. Numerical examples include three- and four-nucleon systems interacting via nucleon-nucleon potentials of AV8 type and a 3$\alpha$ system with a nonlocal $\alpha\alpha$ potential. The results using the explicitly correlated Gaussian basis with the global vectors are shown to be in good agreement with those of other methods. A unique role of the unnatural parity component, caused by the tensor force, is clarified in the $0^-_1$ state of $^4$He. Two-particle correlation function is calculated in the coordinate and momentum spaces to show different characteristics of the interactions employed.
We present a systematic analysis of the extended X-ray emission discovered around 35 FR II radio galaxies from the revised Third Cambridge catalog (3CR) Chandra Snapshot Survey with redshifts between 0.05 to 0.9.   We aimed to (i) test for the presence of extended X-ray emission around FR II radio galaxies, (ii) investigate if the extended emission origin is due to Inverse Compton scattering of seed photons arising from the Cosmic Microwave Background (IC/CMB) or to thermal emission from an intracluster medium (ICM) and (iii) test the impact of this extended emission on hotspot detection.   We investigated the nature of the extended X-ray emission by studying its morphology and compared our results with low-frequency radio observations (i.e., $\sim$150 MHz), in the TGSS and LOFAR archives, as well as with optical images from Pan-STARRS. In addition, we optimized a search for X-ray counterparts of hotspots in 3CR FR II radio galaxies.   We found statistically significant extended emission ($>$3$\sigma$ confidence level) along the radio axis for $\sim$90%, and in the perpendicular direction for $\sim$60% of our sample. We confirmed the detection of 7 hotspots in the 0.5 - 3 keV.   In the cases where the emission in the direction perpendicular to the radio axis is comparable to that along the radio axis, we suggest that the underlying radiative process is thermal emission from ICM. Otherwise, the dominant radiative process is likely non-thermal IC/CMB emission from lobes. We found that non-thermal IC/CMB is the dominant process in $\sim$70% of the sources in our sample, while thermal emission from the ICM dominates in $\sim$15% of them.
The structure of bundles of single-walled carbon nanotubes (SWNT) has been refined by Rietveld analysis using neutron and X-ray powder diffraction data. Based on previous simulation studies of powder diffraction data of SWNT and standard Rietveld analyses, we have developed a pattern fit technique for SWNT which provides precise structure parameters. We also show that the present technique can be used with the maximum entropy method (MEM), which is complementary to the Rietveld analysis. Using the neutron diffraction data of pristine SWNT, we have successfully reconstructed the density of carbon nuclei and zero density in the inner cavity of SWNT by MEM.
It is establish regularity results for weak solutions of quasilinear elliptic problems driven by the well known $\Phi$-Laplacian operator given by \begin{equation*}   \left\{\   \begin{array}{cl}   \displaystyle-\Delta_\Phi u= g(x,u), & \mbox{in}~\Omega,   u=0, & \mbox{on}~\partial \Omega,   \end{array}   \right.   \end{equation*} where $\Delta_{\Phi}u :=\mbox{div}(\phi(|\nabla u|)\nabla u)$ and $\Omega\subset\mathbb{R}^{N}, N \geq 2,$ is a bounded domain with smooth boundary $\partial\Omega$. Our work concerns on nonlinearities $g$ which can be homogeneous or non-homogeneous. For the homogeneous case we consider an existence result together with a regularity result proving that any weak solution remains bounded. Furthermore, for the non-homogeneous case, the nonlinear term $g$ can be subcritical or critical proving also that any weak solution is bounded. The proofs are based on Moser's iteration in Orclicz and Orlicz-Sobolev spaces.
We present preliminary results from our spectroscopic search for planets within 1 AU of metal-poor field dwarfs using NASA time with HIRES on Keck I. The core accretion model of gas giant planet formation is sensitive to the metallicity of the raw material, while the disk instability model is not. By observing metal-poor stars in the field we eliminate the role of dynamical interactions in dense stellar environments, such as a globular cluster. The results of our survey should allow us to distinguish the relative roles of the two competing giant planet formation scenarios.
We derive a Higgs inflationary model in the context of holographic cosmology, where we consider a universe filled with a Higgs field non-minimally coupled to gravity in a slow-roll regime. The amplitude of density (scalar) perturbations is calculated. In this regard, we show that the background and perturbative parameters characterising the inflationary era are related to the standard one through corrections terms. We found that for the e-fold number $N\sim 58$, the spectral index,$n_{r}$, and the tensor-to-scalar ratio,$r$, values are $0.965$ and $0.021$, respectively, which are in agreement with 2018 Planck observational data. However, as soon as we move from $N\sim 58$, the model is ruled out by the current data.
We develop high temperature series expansions for the thermodynamic properties of the honeycomb-lattice Kitaev-Heisenberg model. Numerical results for uniform susceptibility, heat capacity and entropy as a function of temperature for different values of the Kitaev coupling $K$ and Heisenberg exachange coupling $J$ (with $|J|\le |K|$) are presented. These expansions show good convergence down to a temperature of a fraction of $K$ and in some cases down to $T=K/10$. In the Kitaev exchange dominated regime, the inverse susceptibility has a nearly linear temperature dependence over a wide temperature range. However, we show that already at temperatures $10$-times the Curie-Weiss temperature, the effective Curie-Weiss constant estimated from the data can be off by a factor of 2. We find that the magnitude of the heat capacity maximum at the short-range order peak, is substantially smaller for small $J/K$ than for $J$ of order or larger than $K$. We suggest that this itself represents a simple marker for the relative importance of the Kitaev terms in these systems. Somewhat surprisingly, both heat capacity and susceptibility data on Na$_2$IrO$_3$ are consistent with a dominant {\it antiferromagnetic} Kitaev exchange constant of about $300-400$ $K$.
We extend the validity of a simple method for the existence of a density for stochastic differential equations, first introduced in [DebRom2014], by proving local estimate for the density, existence for the density with summable drift, and by improving the regularity of the density.
We present observations of the recently discovered supernova 2008iz in M82 with the VLBI High Sensitivity Array at 22 GHz, the Very Large Array at frequencies of 1.4, 4.8, 8.4, 22 and 43 GHz, and the Chandra X-ray observatory. The supernova was clearly detected on two VLBI images, separated by 11 months. The source shows a ring-like morphology and expands with a velocity of ~23000 km/s. The most likely explosion date is in mid February 2008. The measured expansion speed is a factor of ~2 higher than expected under the assumption that synchrotron self-absorption dominates the light curve at the peak, indicating that this absorption mechanism may not be important for the radio emission. We find no evidence for an asymmetric explosion. The VLA spectrum shows a broken power law, indicating that the source was still optically thick at 1.4 GHz in April 2009. Finally, we report upper limits on the X-ray emission from SN 2008iz and a second radio transient recently discovered by MERLIN observations.
Classical bremsstrahlung of a massless scalar field $\Phi$ is studied in gravity mediated ultra-relativistic collisions with impact parameter $b$ of two massive point particles in the presence of $d$ non-compact or toroidal extra dimensions. The spectral and angular distribution of the scalar radiation are analyzed, while the total emitted $\Phi-$energy is found to be strongly enhanced by a $d-$dependent power of the Lorentz factor $\gamma$. The direct radiation amplitude from the accelerated particles is shown to interfere destructively (in the first two leading ultra-relativistic orders) with the one due to the $\Phi-\Phi-graviton$ interaction in the frequency regime $\gamma/b\lesssim \omega \lesssim \gamma^2/b$ in all dimensions.
In this paper we prove the algebraic-tropical correspondence for stable maps of rational curves with marked points to toric varieties such that the marked points are mapped to given orbits in the big torus and in the boundary divisor, the map has prescribed tangency to the boundary divisor, and certain quadruples of marked points have prescribed cross-ratios. In particular, our results generalize the results of Nishinou and Siebert. The proof is very short, involves only the standard theory of schemes, and works in arbitrary characteristic (including the mixed characteristic case).
We consider three states which are likely to be realized in bi-layer quantum Hall systems at total Landau level filling fraction ${\nu_T}=1$. Two of these states may be understood as paired states. One can occur as an instability of a compressible state in the large $d/l_B$ limit, where $d$ and $l_B$ are the interlayer distance and magnetic length. The other is the $(1,1,1)$ state, which is expected in the small $d/l_B$ limit. We propose that the longitudinal and Hall drag resistivities can be used to distinguish these different quantum Hall states. The drag resistivities may be computed in a straightforward manner using the paired state formulation.
Let \mathcal{F}_k denote the family of 2-edge-colored complete graphs on 2k vertices in which one color forms either a clique of order k or two disjoint cliques of order k. Bollob\'as conjectured that for every \epsilon>0 and positive integer k there is an n(k,\epsilon) such that every 2-edge-coloring of the complete graph of order n \geq n(k,\epsilon) which has at least \epsilon {n \choose 2} edges in each color contains a member of \mathcal{F}_k. This conjecture was proved by Cutler and Mont\'agh, who showed that n(k,\epsilon)<4^{k/\epsilon}. We give a much simpler proof of this conjecture which in addition shows that n(k,\epsilon)<\epsilon^{-ck} for some constant c. This bound is tight up to the constant factor in the exponent for all k and \epsilon. We also discuss similar results for tournaments and hypergraphs.
We prove the existence of one quarter supersymmetric type IIB configurations that arise as non-trivial scaling solutions of the standard five dimensional Kerr-AdS black holes by the explicit construction of its Killing spinors. This neutral, spinning solution is asymptotic to the static anti-deSitter space-time with cosmological constant $-\textstyle{\frac{1}{\ell^2}}$, it has two finite equal angular momenta $J_1=\pm J_2$, mass $M=\textstyle{\frac{1}{\ell}} (|J_1|+|J_2|)$ and a naked singularity.We also address the scaling limit associated with one half supersymmetric solution with only one angular momentum.
Let $d_{\alpha, \beta}(n)=\sum\limits_{\substack{n=kl \alpha l<k\leq\beta l}}1$ be the number of ways of factoring n into two almost equal integers. For rational numbers $0<\alpha <\beta $, we consider the following Zeta function $\zeta_{\alpha,\beta}(s)=\sum\limits_{n=1}^{\infty}\frac{d_{\alpha, \beta}(n)}{n^{s}}$ for $\Re s>1.$ It has an analytic continuation to $\Re s>1/3.$ We get an asymptotic formula for the mean square of $\zeta_{\alpha,\beta}(s)$ in the strip $1/2<\Re s<1$. As an application, we improve an result on the distribution of primitive Pythagorean triangles.
We study intrinsic DC spin and valley Hall conductivity in doped ferromagnetic silicene in the presence of an electric filed applied perpendicular to silicene sheet. By calculating its energy spectrum and wavefunction and by making use of Kubo formalism, we obtain a general relation for the transverse Hall conductivity which can be used to obtain spin- and valley-Hall conductivity. Our results, in the zero limit of the exchange field, reduces to the previous results. Furthermore we discuss electrically tunable spin and valley polarized transport in ferromagnetic silicene and obtain the necessary conditions for observing a fully spin or valley polarized transport.
A family of perfect matchings of $K_{2n}$ is $t$-$intersecting$ if any two members share $t$ or more edges. We prove for any $t \in \mathbb{N}$ that every $t$-intersecting family of perfect matchings has size no greater than $(2(n-t) - 1)!!$ for sufficiently large $n$, and that equality holds if and only if the family is composed of all perfect matchings that contain a fixed set of $t$ disjoint edges. This is an asymptotic version of a conjecture of Godsil and Meagher that can be seen as the non-bipartite analogue of the Deza-Frankl conjecture proven by Ellis, Friedgut, and Pilpel.
The accelerated expansion of the universe is ascribed to the existence of dark energy. Black holes accretion of dark energy induces a mass change proportional to the energy density and pressure of the background dark energy fluid. The time scale during which the mass of black holes changes considerably is too long relative to the age of the universe, thus beyond detection possibilities. We propose to take advantage of the modified black hole masses for exploring the equation of state $w[z]$ of dark energy, by investigating the evolution of supermassive black hole binaries on a dark energy background. Deriving the signatures of dark energy accretion on the evolution of binaries, we find that dark energy imprints on the emitted gravitational radiation and on the changes in the orbital radius of the binary can be within detection limits for certain supermassive black hole binaries. In this talk I describe how binaries can provide a useful tool in obtaining complementary information on the nature of dark energy, based on the work done with A.Kelleher.
Context. Luminous Blue Variables (LBVs) are thought to be in a transitory phase between O stars on the main-sequence and the Wolf-Rayet stage. Recent studies suggest that they might be formed through binary interaction. Only a few are known in binary systems but their multiplicity fraction is uncertain. Aims. This study aims at deriving the binary fraction among the Galactic (confirmed and candidate) LBV population. We combine multi-epoch spectroscopy and long-baseline interferometry. Methods. We use cross-correlation to measure their radial velocities. We identify spectroscopic binaries through significant RV variability (larger than 35 km/s). We investigate the observational biases to establish the intrinsic binary fraction. We use CANDID to detect interferometric companions, derive their parameters and positions. Results. We derive an observed spectroscopic binary fraction of 26 %. Considering period and mass ratio ranges from Porb=1 to 1000 days, and q = 0.1-1.0, and a representative set of orbital parameter distributions, we find a bias-corrected binary fraction of 62%. From interferometry, we detect 14 companions out of 18 objects, providing a binary fraction of 78% at projected separations between 1 and 120 mas. From the derived primary diameters, and the distances of these objects, we measure for the first time the exact radii of Galactic LBVs to be between 100 and 650 Rsun, making unlikely to have short-period systems. Conclusions. This analysis shows that the binary fraction among the Galactic LBV population is large. If they form through single-star evolution, their orbit must be initially large. If they form through binary channel that implies that either massive stars in short binary systems must undergo a phase of fully non-conservative mass transfer to be able to sufficiently widen the orbit or that LBVs form through merging in initially binary or triple systems.
The temperature dependence of the manganese magnetic moment and the spin-lattice relaxation rate measured by the muon spin relaxation technique in the magnetically ordered phase of the chiral intermetallic cubic MnSi system are both explained in terms of helimagnon excitations of a localized spin model. The two free parameters characterizing the helimagnon dispersion relation are determined. A combined analysis of the two data sets cannot be achieved using the self-consistent renormalization theory of spin fluctuations which assumes the magnetism of MnSi to arise uniquely from electronic bands. As a result of this work, MnSi is proposed to be a dual electronic system composed of localized and itinerant magnetic electrons. Finally we note that the analysis framework can be applied to other helimagnets such as the magnetoelectric compound Cu2OSeO3.
Motivated by forthcoming experiments at RHIC and LHC, we study event-by-event fluctuations in ultrarelativistic heavy-ion collisions in participant nucleon as well as thermal models. The calculated physical observables, including multiplicity, kaon to pion ratios, and transverse momenta agree well with recent NA49 data at the SPS, and indicate that such studies do not yet reveal the presence of new physics. Finally, we present a simple model of how a first order phase transition can be signaled by very large fluctuations.
The cross section for elastic vector meson production in photon-proton interactions at large $t$ is considered using the exact analytic solution of the BFKL equation in the azimuthally symmetric $n=0$ limit. We use a non-relativistic model for the vector meson production and find a small shrinkage in the $t$-distribution with increasing energy.
The nonabelian Berry phase is computed in the T dualized quantum mechanics obtained from the USp(2k) matrix model. Integrating the fermions, we find that each of the spacetime points X_{\nu}^{(i)} is equipped with a pair of su(2) Lie algebra valued pointlike singularities located at a distance m_{(f)} from the orientifold surface. On a four dimensional paraboloid embedded in the five dimensional Euclidean space, these singularities are recognized as the BPST instantons.