ShantanuT01/DACTYL-Pretraining huggingface dataset:
The measurement device independent (MDI) Quantum Key Distribution (QKD) is a practically implementable method for transmitting secret keys between respective partners performing quantum communication. SARG04 (Scarani-Ac\`{i}n-Ribordy-Gisin 2004) is a protocol tailored to struggle against photon number splitting (PNS) attacks by eavesdroppers and its MDI-QKD version is reviewed and optimized from secret key bitrate versus communication distance point of view. We consider the effect of several important factors such as error correction function, dark counting parameter and quantum efficiency in order to achieve the largest key bitrate versus longest communication distance.
We present high spatial resolution observations of ground-state OH masers achieved with the Australia Telescope Compact Array (ATCA). These observations targeted 253 pointing centres containing OH maser candidates at all four ground-state OH transitions identified in the Southern Parkes Large-Area Survey in Hydroxyl (SPLASH) across 96 square degrees of the Southern Galactic plane (332\degree$<l<$334\degree and $-$2\degree$<b<+$2\degree, 344\degree$<l<$355\degree and $-$2\degree$<b<+$2\degree, 358\degree$<l<$4\degree and $+$2\degree$<b<+$6\degree, 5\degree$<l<$10\degree and $-$2\degree$<b<+$2\degree). We detect maser emission towards 236 fields and suggest that 7 out of 17 non-detections are due to the slightly lower sensitivity of the ATCA observations, combined with some temporal variability. The superior resolution provided by the ATCA data has allowed us to identify 362 OH maser sites in the 236 target fields. Almost half (160 of 362) of these masers have been detected for the first time. Comparison between these 362 maser sites with information presented in the literature allowed us to categorize 238 sites as evolved star sites (66\%), 63 as star formation (17\%), eight as supernova remnants and 53 unknown maser sites (15\%). We present analysis of the OH masers across the full SPLASH survey range (176 square degrees) and find that the detection rate of 1.7 GHz radio continuum sources (18\%) is lower than that previously found at 8.2 and 9.2 GHz (38\%). We also find that the velocity separations of evolved star sites with symmetric 1612 MHz maser profiles are generally smaller than those with asymmetric profiles.
Variational formulas for the Laplace transform of the exit time from an open set of a Hunt process generated by a regular lower bounded semi-Dirichlet form are established. While for symmetric Markov processes, variational formulas are derived for the exponential moments of the exit time. As applications, we provide some comparison theorems and quantitative relations of the exponential moments and Poincar\'e inequalities.
We consider the classical evolution of the inflaton field $\phi(t)$ and the Hubble parameter $H(t)$ in homogeneous and isotropic single-field inflation models. Under an extremely broad assumption, we show that the universe generically emerges from an initial singularity in a non-inflating state where the kinetic energy of the inflaton dominates its potential energy, $\dot{\phi}^2 \gg V(\phi)$. In this kinetically-dominated regime, the dynamical equations admit simple analytic solutions for $\phi(t)$ and $H(t)$, which are independent of the form of $V(\phi)$. In such models, these analytic solutions thus provide a simple way of setting the initial conditions from which to start the (usually numerical) integration of the coupled equations of motion for $\phi(t)$ and $H(t)$. We illustrate this procedure by applying it to spatially-flat models with polynomial and exponential potentials, and determine the background evolution in each case; generically $H(t)$ and $|\phi(t)|$ as well as their time derivatives decrease during kinetic dominance until $\dot{\phi}^2\sim V(\phi)$, marking the onset of a brief period of fast-roll inflation prior to a slow roll phase. We also calculate the approximate spectrum of scalar perturbations produced in each model and show that it exhibits a generic damping of power on large scales. This may be relevant to the apparent low-$\ell$ falloff in the CMB power spectrum.
If light--flavor squarks and gluinos are indeed heavy and chargino pair production is plagued with overwhelming backgrounds, pair production and associated production of stops and charginos will become the key signatures in the upcoming LHC runs. We present fully automated next-to-leading order predictions for heavy flavor squark production at the LHC, including stop-chargino associated production, based on MadGolem. We compute the total and differential NLO rates for a variety of MSSM scenarios with a light third generation. We focus on theoretical uncertainties on differential rates, including a comparison to multi-jet merging and the impact of bottom parton densities for stop-chargino associated production. We find that for the associated production channel the rates can reach tens of femtobarns, but the scale dependence does not provide a conservative estimate of the theoretical uncertainties.
The prototype of the Beta Cep class of pulsating stars, Beta Cep, rotates relatively slowly, and yet displays episodic Halpha emission. Such behaviour is typical of a classical Be star. For some time this posed a contradiction to our understanding of the Be phenomena as rapid rotation is thought to be a prerequisite for the emission phases of Be stars. Recent work has demonstrated that the Halpha emission is in fact due to a close companion (separation ~0.25") of the star. This resolves the apparent enigma if this close companion is a classical Be star. We aim to test the hypothesis that this close companion is a valid Be star by determining properties such as its spectral type and vsin i. We employed spectroastrometry to investigate the close binary system. Using the spectroastrometric signatures observed, we split the composite binary spectra into its constituent spectra in the B band and R band. The split spectra allow us to estimate spectral types of the binary components. We find that the primary of the close binary system has a spectral type of B2III and the secondary a spectral type of B5Ve. From the relationship between mass and spectral type, we determine the masses of the binary components to be M_p = 12.6+/-3.2 M_* and M_s = 4.4+/-0.7 M_* respectively. The spectroastrometric data allow some constraint on the orbit, and we suggest a moderate revision to the previously determined orbit. We confirm that the primary of the system is a slow rotator (vsin i =29 +43/-29 km/s), while the secondary rotates significantly faster, at a vsin i =230+/-45 km/s. We show that the close companion to the beta Cep primary is a valid classical Be star. It has a spectral type of B5Ve and is a relatively fast rotator.
Another introduction to perverse sheaves with some exercises. Expanded version of five lectures at the 2015 PCMI.
How can probabilities make sense in a deterministic many-worlds theory? We address two facets of this problem: why should rational agents assign subjective probabilities to branching events, and why should branching events happen with relative frequencies matching their objective probabilities. To address the first question, we generalise the Deutsch-Wallace theorem to a wide class of many-world theories, and show that the subjective probabilities are given by a norm that depends on the dynamics of the theory: the 2-norm in the usual Many-Worlds interpretation of quantum mechanics, and the 1-norm in a classical many-worlds theory known as Kent's universe. To address the second question, we show that if one takes the objective probability of an event to be the proportion of worlds in which this event is realised, then in most worlds the relative frequencies will approximate well the objective probabilities. This suggests that the task of determining the objective probabilities in a many-worlds theory reduces to the task of determining how to assign a measure to the worlds.
X-ray spectral analysis of quiescent low-mass X-ray binaries (LMXBs) has been one of the most common tools to measure the radius of neutron stars (NSs) for over a decade. So far, this method has been mainly applied to NSs in globular clusters, primarily because of their well-constrained distances. Here, we study Chandra data of seven transient LMXBs in the Galactic plane in quiescence to investigate the potential of constraining the radius (and mass) of the NSs inhabiting these systems. We find that only two of these objects had X-ray spectra of sufficient quality to obtain reasonable constraints on the radius, with the most stringent being an upper limit of $R\lesssim$14.5 km for EXO 0748-676 (for assumed ranges for mass and distance). Using these seven sources, we also investigate systematic biases on the mass/radius determination; for Aql X-1 we find that omitting a power-law spectral component when it does not seem to be required by the data, results in peculiar trends in the obtained radius with changing mass and distance. For EXO 0748-676 we find that a slight variation in the lower limit of the energy range chosen for the fit leads to systematically different masses and radii. Finally, we simulated Athena spectra and found that some of the biases can be lifted when higher quality spectra are available and that, in general, the search for constraints on the equation of state of ultra-dense matter via NS radius and mass measurements may receive a considerable boost in the future.
It is shown that Connes' generalized gauge field in non-commutative geometry is derived by simply requiring that Dirac lagrangian be invariant under local transformations of the unitary elements of the algebra, which define the gauge group. The spontaneous breakdown of the gauge symmetry is guaranteed provided the chiral fermions exist in more than one generations as first observed by Connes-Lott. It is also pointed out that the most general gauge invariant lagrangian in the bosonic sector has two more parameters than in the original Connes-Lott scheme.
We perform a comparison of the properties of galaxies in compact groups, loose groups and in the field to deepen our understanding of the physical mechanisms acting upon galaxy evolution in different environments. We select samples of galaxies in compact groups identified by McConnachie et al., loose groups identified by Zandivarez and Martinez, and field galaxies from the Sloan Digital Sky Survey. We compare properties of the galaxy populations in these different environments: absolute magnitude, colour, size, surface brightness, stellar mass and concentration. We also study the fraction of red and early type galaxies, the luminosity function, the colour-luminosity and luminosity-size relations. The population of galaxies in compact groups differ from that of loose groups and the field. The fraction of read and early type galaxies is higher in compact groups. On average, galaxies in compact groups are systematically smaller, more concentrated and have higher surface brightness than galaxies in the field and in loose groups. For fixed absolute magnitude, or fixed surface brightness, galaxies in compact groups are smaller. The physical mechanisms that transform galaxies into earlier types could be more effective within compact groups given the high densities and low velocity dispersion that characterise that particular environment, this could explain the large fraction of red and early type galaxies we found in compact groups. Galaxies inhabiting compact groups have undergone a major transformation compared to galaxies that inhabit loose groups.
The integer and fractional quantum Hall states are known to break down at high dc bias, exhibiting deviation from the ideal incompressible behavior. We measure breakdown of the \nu = 2, 3, 4, 5 integer and the \nu = 4/3 and 5/3 fractional states in a quantum point contact (QPC) of lithographic width ~600 nm. Dependence of the critical current on magnetic field, QPC gate voltage, and QPC width are presented. Of particular interest, the critical current of the 4/3 and 5/3 fractional states shows the opposite dependence on QPC width compared to the integer states. This previously unobserved result is not explained by current theories of breakdown.
We present an ab initio modeling framework to simulate Majorana transport in 2D semiconducting materials, paving the way for topological qubits based on 2D nanoribbons. By combining density-functional-theory and quantum transport calculations, we show that the signature of Majorana bound states (MBSs) can be found in 2D material systems as zero-energy modes with peaks in the local density-of-states. The influence of spin-orbit coupling and external magnetic fields on Majorana transport is studied for two relevant 2D materials, WSe2 and PbI2. To illustrate the capabilities of the proposed ab initio platform, a device structure capable of hosting MBSs is created from a PbI2 nanoribbon and carefully investigated. These results are compared to InSb nanowires and used to provide design guidelines for 2D topological qubits.
The top-hat spherical collapse model (TSC) is one of the most fundamental analytical frameworks to describe the non-linear growth of cosmic structure. TSC has motivated, and been widely applied in, various researches even in the current era of precision cosmology. While numerous studies exist to examine its validity against numerical simulations in a statistical fashion, there are few analyses to compare the TSC dynamics in an individual object-wise basis, which is what we attempt in the present paper. We extract 100 halos at z = 0 from a cosmological N-body simulation according to the conventional TSC criterion for the spherical over-density. Then we trace back their spherical counter-parts at earlier epochs. Just prior to the turn-around epoch of the halos, their dynamics is well approximated by TSC, but their turn-around epochs are systematically delayed and the virial radii are larger by ~ 20 percent on average relative to the TSC predictions. We find that this systematic deviation is mainly ascribed to the non-uniformity/inhomogeneity of dark matter density profiles and the non-zero velocity dispersions, both of which are neglected in TSC. In particular, the inside-out-collapse and shell-crossing of dark matter halos play an important role in generating the significant velocity dispersion. The implications of the present result are briefly discussed.
We study the abundance of substructure in the matter density near galaxies using ALMA Science Verification observations of the strong lensing system SDP.81. We present a method to measure the abundance of subhalos around galaxies using interferometric observations of gravitational lenses. Using simulated ALMA observations, we explore the effects of various systematics, including antenna phase errors and source priors, and show how such errors may be measured or marginalized. We apply our formalism to ALMA observations of SDP.81. We find evidence for the presence of a $M=10^{8.96\pm 0.12} M_{\odot}$ subhalo near one of the images, with a significance of $6.9\sigma$ in a joint fit to data from bands 6 and 7; the effect of the subhalo is also detected in both bands individually. We also derive constraints on the abundance of dark matter subhalos down to $M\sim 2\times 10^7 M_{\odot}$, pushing down to the mass regime of the smallest detected satellites in the Local Group, where there are significant discrepancies between the observed population of luminous galaxies and predicted dark matter subhalos. We find hints of additional substructure, warranting further study using the full SDP.81 dataset (including, for example, the spectroscopic imaging of the lensed carbon monoxide emission). We compare the results of this search to the predictions of $\Lambda$CDM halos, and find that given current uncertainties in the host halo properties of SDP.81, our measurements of substructure are consistent with theoretical expectations. Observations of larger samples of gravitational lenses with ALMA should be able to improve the constraints on the abundance of galactic substructure.
Context: Stars with about 1$-$2 solar masses at the red giant branch (RGB) represent an intriguing period of stellar evolution, i.e. when the convective envelope interacts with the fast-rotating core. During these mixing episodes freshly synthesized lithium can come up to the stellar surface along with high angular momentum material. This high angular momentum may alter the surface rotation pattern.   Aims: The single rapidly rotating K-giant V1192 Ori is revisited to determine its surface differential rotation, lithium abundance, and basic stellar properties such as a precise rotation period. The aim is to independently verify the antisolar differential rotation of the star and possibly find a connection to the surface lithium abundance.   Methods: We applied time-series Doppler imaging to a new multi-epoch data set. Altogether we reconstructed 11 Doppler images from spectroscopic data collected with the STELLA robotic telescope between 2007--2016. We used our inversion code iMap to reconstruct all stellar surface maps. We extracted the differential rotation from these images by tracing systematic spot migration as a function of stellar latitude from consecutive image cross-correlations.   Results: The position of V1192 Ori in the Hertzsprung-Russell diagram suggests that the star is in the helium core-burning phase just leaving the RGB bump. We measure $A({\rm Li})_{\rm NLTE}=1.27$, i.e. a value close to the anticipated transition value of 1.5 from Li-normal to Li-rich giants. Doppler images reveal extended dark areas arranged quasi-evenly along an equatorial belt. No cool polar spot is found during the investigated epoch. Spot displacements clearly suggest antisolar surface differential rotation with $\alpha=-0.11\pm0.02$ shear coefficient.   Conclusions: The surface Li enrichment and the peculiar surface rotation pattern may indicate a common origin.
We investigate the supernova explosions that end the lives of massive Population III stars in low-mass minihalos (M~10^6 M_sun) at redshifts z~20. Employing the smoothed particle hydrodynamics method, we carry out numerical simulations in a cosmological set-up of pair-instability supernovae with explosion energies of E_SN=10^51 and 10^53 ergs. We find that the more energetic explosion leads to the complete disruption of the gas in the minihalo, whereas the lower explosion energy leaves much of the halo intact. The higher energy supernova expels > 90% of the stellar metals into a region ~1 kpc across over a timescale of 3-5 Myr. Due to this burst-like initial star formation episode, a large fraction of the universe could have been endowed with a metallicity floor, Z_min>10^-4 Z_sun, already at z>15.
The hive model is a combinatorial device that may be used to determine Littlewood-Richardson coefficients and study their properties. It represents an alternative to the use of the Littlewood-Richardson rule. Here properties of hives are used to determine all possible multiplicity-free Schur function products and skew Schur function expansions. This confirms the results of Stembridge, Gutschwager, and Thomas and Yong, and sheds light on the combinatorial origin of the conditions for being multiplicity-free, as well as illustrating some of the key features and power of the hive model.
We construct a single scalar field model with tachyon field non-minimally coupled to itself, its derivative and to the curvature. We study the cosmological dynamics of the equation of state in this setup. While it is expected that in the case of single scalar field the crossing of the phantom divide line can not be realized [10], we show that incorporating quantum corrections, namely, non-minimal derivative coupling of scalar field with curvature in our model, lead to phantom divide crossing.
We study the analogy between propagation of light rays in a stationary curved spacetime and in a toroidal (meta-)material. After introducing a novel gravitational analog of the index of refraction of a magneto-electric medium, it is argued that light rays not only feel a Lorentz-like force in a magneto-electric medium due to the non-vanishing curl of the toroidal moment, but also there exists an optical analog of Aharonov-Bohm effect for the rays traveling in a region with a curl-free toroidal moment. Experimental realization of this effect could utilize either a multiferroic material or a toroidal metamaterial.
We continue our empirical study of the emission line flux originating in the cool ($T\sim10^4$ K) gas that populates the halos of galaxies and their environments. Specifically, we present results obtained for a sample of nearly half a million individual galaxies, groups, and clusters of galaxies, intersected by more than two million SDSS lines of sight at projected separations of up to a quarter of the virial radius. Adopting simple power law relationships between the circumgalactic (CGM) cool gas fraction and either the halo or stellar mass, we present expressions for the CGM cool gas fraction as a function of either halo or stellar mass, $f_{\rm cool}(M_h) = (0.25^{+0.07}_{-0.06}) \times (M_h/10^{12}M_\odot)^{(-0.39^{+0.06}_{-0.07})}$ or $f_{\rm cool}(M_{*}) = (0.28^{+0.07}_{-0.06}) \times (M_{\rm *}/10^{10.0}M_\odot)^{(-0.33\pm 0.06)}$. Where we can compare, our results are consistent with previous constraints from absorption line studies, our own previous emission line work, and simulations. The cool gas can be the dominant baryonic CGM component, comprising a fraction as high as $> 90\%$ of halo gaseous baryons, in low mass halos, $M_h\sim$ $10^{10.5} M_\odot$, and a minor fraction, $<$ 5\%, in groups and clusters, $M_h > 10^{14} M_\odot$.
The dc conductance of a short spin-incoherent Hubbard chain coupled to leads is investigated using quantum Monte Carlo calculations. In contrast with the Luttinger liquid regime, where the conductance is equal to the noninteracting value, the spin-incoherent regime displays a conductance that decreases rapidly with chain length down to a value of roughly 1.5e2/h for a four site chain followed by a slower decrease for longer chains. We also discuss the resistance contribution from scattering in the contacts.
Kesten and Lee [36] proved that the total length of a minimal spanning tree on certain random point configurations in $\mathbb{R}^d$ satisfies a central limit theorem. They also raised the question: how to make these results quantitative? However, techniques employed to tackle the same problem for other functionals studied in geometric probability do not apply directly to the minimal spanning tree. Thus the problem of determining the convergence rate in the central limit theorem for Euclidean minimal spanning trees has remained open. In this work, we establish bounds on the convergence rate for the Poissonized version of this problem by using a variation of Stein's method. We also derive bounds on the convergence rate for the analogous problem in the setup of the lattice $\mathbb{Z}^d$.   The contribution of this paper is twofold. First, we develop a general technique to compute convergence rates in central limit theorems satisfied by minimal spanning trees on sequence of weighted graphs which includes minimal spanning trees on Poisson points. Secondly, we present a way of quantifying the Burton-Keane argument for the uniqueness of the infinite open cluster. The latter is interesting in its own right and based on a generalization of our technique, Duminil-Copin, Ioffe and Velenik [28] have recently obtained bounds on probability of two-arm events in a broad class of translation-invariant percolation models.