Integral cross sections for optically allowed electronic-state excitations of atoms and molecules by electron impact, by applying scaled plane-wave Born models, are reviewed. Over 40 years ago, ...Inokuti presented an influential review of charged-particle scattering, based on the theory pioneered by Bethe forty years earlier, which emphasized the importance of reliable cross-section data from low eV energies to high keV energies that are needed in many areas of radiation science with applications to astronomy, plasmas, and medicine. Yet, with a couple of possible exceptions, most computational methods in electron-atom scattering do not, in general, overlap each other's validity range in the region from threshold up to 300 eV and, in particular, in the intermediate region from 30 to 300 eV. This is even more so for electron-molecule scattering. In fact this entire energy range is of great importance and, to bridge the gap between the two regions of low and high energy, scaled plane-wave Born models were developed to provide reliable, comprehensive, and absolute integral cross sections, first for ionization by Kim and Rudd and then extended to optically allowed electronic-state excitation by Kim. These and other scaling models in a broad, general application to electron scattering from atoms and molecules, their theoretical basis, and their results for cross sections along with comparison to experimental measurements are reviewed. Where possible, these data are also compared to results from other computational approaches.
This paper presents the results of a survey exploring the determinants of vacinees' confidence in COVID-19 vaccines and their motivations to become vaccinated. At the threatening rise of the highly ...infectious Omicron variant, in December 2021, we interviewed people in waiting lines of vaccination centers. Our results identify risk-averse and social-distancing-compliant people as showing high confidence in the vaccine, which motivates them to receive it for reasons of protecting themselves and others. By contrast, policy incentives, such as "3G/2G" restrictions, motivate risk-tolerant people who opted for vaccination to get access to public areas. Trusting people who regularly vote are little afraid of vaccines' side effects. Our findings offer insights for policymakers in societies and firms that help to tailor policies promoting vaccination based on people's economic preferences.
Abstract
We release the AllWISE counterparts and Gaia matches to 106 573 and 17 665 X-ray sources detected in the ROSAT 2RXS and XMMSL2 surveys with |b| > 15°. These are the brightest X-ray sources ...in the sky, but their position uncertainties and the sparse multi-wavelength coverage until now rendered the identification of their counterparts a demanding task with uncertain results. New all-sky multi-wavelength surveys of sufficient depth, like AllWISE and Gaia, and a new Bayesian statistics based algorithm, Nway, allow us, for the first time, to provide reliable counterpart associations. Nway extends previous distance and sky density based association methods and, using one or more priors (e.g. colours, magnitudes), weights the probability that sources from two or more catalogues are simultaneously associated on the basis of their observable characteristics. Here, counterparts have been determined using a Wide-field Infrared Survey Explorer (WISE) colour-magnitude prior. A reference sample of 4524 XMM/Chandra and Swift X-ray sources demonstrates a reliability of ∼94.7 per cent (2RXS) and 97.4 per cent (XMMSL2). Combining our results with Chandra-COSMOS data, we propose a new separation between stars and AGN in the X-ray/WISE flux-magnitude plane, valid over six orders of magnitude. We also release the Nway code and its user manual. Nway was extensively tested with XMM-COSMOS data. Using two different sets of priors, we find an agreement of 96 per cent and 99 per cent with published Likelihood Ratio methods. Our results were achieved faster and without any follow-up visual inspection. With the advent of deep and wide area surveys in X-rays (e.g. SRG/eROSITA, Athena/WFI) and radio (ASKAP/EMU, LOFAR, APERTIF, etc.) Nway will provide a powerful and reliable counterpart identification tool.
This paper analyzes gender differences in the disposition effect in an experiment based on Weber and Camerer (1998). The results emphasize that female investors realize less capital losses, have ...significantly higher disposition effects and are more loss averse than men.
•Analysis of Gender Differences in the Disposition effects in a controlled experiment.•Male and female investors both sell more capital gains than capital losses.•Women have higher disposition effects than men and behave more loss averse.•The disposition effect is exclusively driven by women’s reluctance to sell capital losses.
Quantum discord for qubit-qudit systems Vinjanampathy, Sai; Rau, A R P
Journal of physics. A, Mathematical and theoretical,
03/2012, Letnik:
45, Številka:
9
Journal Article
Recenzirano
Odprti dostop
We present two formulae to calculate quantum discord, a kind of quantum correlation, between a qubit and a second party of arbitrary dimension d. The first formula is the original entropic definition ...and the second is a recently proposed geometric distance measure which leads to an analytical formulation. The tracing over the qubit in the entropic calculation is reduced to a very simple prescription. And, when the d-dimensional system is a so-calledX-state, the density matrix having non-zero elements only along the diagonal and anti-diagonal, the entropic calculation can also be carried out analytically. Such states of the full bipartite qubit-qudit system may be named 'extended X-states', whose density matrix is built of four block matrices, each visually appearing as an X. The optimization involved in the entropic calculation is generally over two parameters, reducing to one for many cases, and avoided altogether for an overwhelmingly large set of density matrices as our numerical investigations demonstrate. In the case of N = 2, extended X-states encompass the entire 15-dimensional parameter space, that is, they represent the full qubit-qubit system.
ABSTRACT
White dwarf black hole tidal disruption events (herein WTDEs) present an opportunity to probe the quiescent intermediate mass black hole population in the Universe. We run an extensive set ...of Monte Carlo based simulations to explore SRG/eROSITA’s detection sensitivity to WTDEs as a function of black hole mass, redshift, and time offset between event flaring and it first being observed. A novel estimate of WTDE rate densities from globular clusters and dwarf galaxies is also presented. We combine this with estimated detection sensitivities to infer the rate of eROSITA detecting these events. Depending on the estimate of the intrinsic rate of WTDEs, we anticipate that eROSITA may detect three events over its 4 yr all-sky survey. eROSITA will be most sensitive to systems with black hole masses above $10^4\, \mathrm{M}_{\odot }$, and is most likely to catch these within 5 d of flaring.
We argue that the ‘changing look’ active galactic nucleus (AGN) recently reported by LaMassa et al. could be a luminous flare produced by the tidal disruption of a supersolar mass star passing just a ...few gravitational radii outside the event horizon of a ∼108 M⊙ nuclear black hole. This flare occurred in a massive, star-forming galaxy at redshift z = 0.312, robustly characterized thanks to repeated late-time photometric and spectroscopic observations. By taking difference photometry of the well-sampled multiyear Sloan Digital Sky Survey (SDSS) Stripe-82 light curve, we are able to probe the evolution of the nuclear spectrum over the course of the outburst. The tidal disruption event (TDE) interpretation is consistent with the very rapid rise and the decay time of the flare, which displays an evolution consistent with the well-known t
−5/3 behaviour (with a clear superimposed re-brightening flare). Our analysis places constraints on the physical properties of the TDE, such as the putative disrupted star's mass and orbital parameters, as well as the size and temperature of the emitting material. The properties of the broad and narrow emission lines observed in two epochs of SDSS spectra provide further constraints on the circum-nuclear structure, and could be indicative that the system hosted a moderate-luminosity AGN as recently as a few 104 yr ago, and is likely undergoing residual accretion as late as 10 yr after peak, as seen from the broad Hα emission line. We discuss the complex interplay between TDEs and gas accretion episodes in galactic nuclei, highlighting the implications for future TDE searches and for estimates of their intrinsic rates.
ABSTRACT
We study the quasi‐simultaneous near‐IR, optical, ultraviolet and X‐ray photometry of 11 γ‐ray selected blazars for which redshift estimates larger than 1.2 have been recently provided. Four ...of these objects turn out to be high‐power blazars with the peak of their synchrotron emission between ∼3 × 1015 and ∼1016 Hz, and therefore of a kind predicted to exist but never seen before. This discovery has important implications for our understanding of physical processes in blazars, including the so‐called ‘blazar sequence’, and might also help in constraining the extragalactic background light through γ‐ray absorption since two sources are strongly detected even in the 10–100 GeV Fermi‐LAT band. Based on our previous work and their high powers, these sources are very likely high‐redshift flat‐spectrum radio quasars, with their emission lines swamped by the non‐thermal continuum.
The symmetry SU(2) and its geometric Bloch Sphere rendering have been successfully applied to the study of a single qubit (spin-1/2); however, the extension of such symmetries and geometries to ...multiple qubits—even just two—has been investigated far less, despite the centrality of such systems for quantum information processes. In the last two decades, two different approaches, with independent starting points and motivations, have been combined for this purpose. One approach has been to develop the unitary time evolution of two or more qubits in order to study quantum correlations; by exploiting the relevant Lie algebras and, especially, sub-algebras of the Hamiltonians involved, researchers have arrived at connections to finite projective geometries and combinatorial designs. Independently, geometers, by studying projective ring lines and associated finite geometries, have come to parallel conclusions. This review brings together the Lie-algebraic/group-representation perspective of quantum physics and the geometric–algebraic one, as well as their connections to complex quaternions. Altogether, this may be seen as further development of Felix Klein’s Erlangen Program for symmetries and geometries. In particular, the fifteen generators of the continuous SU(4) Lie group for two qubits can be placed in one-to-one correspondence with finite projective geometries, combinatorial Steiner designs, and finite quaternionic groups. The very different perspectives that we consider may provide further insight into quantum information problems. Extensions are considered for multiple qubits, as well as higher-spin or higher-dimensional qudits.
PDF
