589 research outputs found
Coherent states for the q-deformed quantum mechanics on a circle
The q-deformed coherent states for a quantum particle on a circle are
introduced and their properties investigated.Comment: 11 pages, 2 PostScript figure
Local thermal equilibrium and ideal gas Stephani universes
The Stephani universes that can be interpreted as an ideal gas evolving in
local thermal equilibrium are determined. Five classes of thermodynamic schemes
are admissible, which give rise to five classes of regular models and three
classes of singular models. No Stephani universes exist representing an exact
solution to a classical ideal gas (one for which the internal energy is
proportional to the temperature). But some Stephani universes may approximate a
classical ideal gas at first order in the temperature: all of them are
obtained. Finally, some features about the physical behavior of the models are
pointed out.Comment: 20 page
On the uncertainty relations and squeezed states for the quantum mechanics on a circle
The uncertainty relations for the position and momentum of a quantum particle
on a circle are identified minimized by the corresponding coherent states. The
sqeezed states in the case of the circular motion are introduced and discussed
in the context of the uncertainty relations.Comment: 4 figure
Dynamics of the Pionium with the Density Matrix Formalism
The evolution of pionium, the hydrogen-like atom, while passing
through matter is solved within the density matrix formalism in the first Born
approximation. We compare the influence on the pionium break-up probability
between the standard probabilistic calculations and the more precise picture of
the density matrix formalism accounting for interference effects. We focus our
general result in the particular conditions of the DIRAC experiment at CERN.Comment: 14 pages, 2 figures, submitted to J. Phys. B: At. Mol. Phy
The gravitational energy-momentum flux
We present a continuity equation for the gravitational energy-momentum, which
is obtained in the framework of the teleparallel equivalent of general
relativity. From this equation it follows a general definition for the
gravitational energy-momentum flux. This definition is investigated in the
context of plane waves and of cylindrical Einstein-Rosen waves. We obtain the
well known value for the energy flux of plane gravitational waves, and conclude
that the latter exhibit features similar to plane electromagnetic waves.Comment: 20 pages, latex file, no figures, two references added, accepted for
publication in Class. Quantum Gravit
Energetics of a black hole: constraints on the jet velocity and the nature of the X-ray emitting region in Cyg X-1
We investigate the energetics of the jet and X-ray corona of Cyg X-1. We show
that the current estimates of the jet power obtained from Halpha and [O III]
measurements of the optical nebula surrounding the X-ray source allow one to
constrain the bulk velocity of the jet. It is definitely relativistic (v >0.1c)
and most probably in the range (0.3-0.8)c. The exact value of the velocity
depends on the accretion efficiency. These constraints are obtained
independently of, and are consistent with, previous estimates of the jet bulk
velocity based on radio measurements. We then show that the X-ray emission does
not originate in the jet. Indeed, the energy budget does not allow the corona
to be ejected to infinity at relativistic speed. Rather, either a small
fraction of the corona escapes to infinity, or the ejection velocity of the
corona is vanishingly low. Although the corona could constitute the jet
launching region, it cannot be identified with the jet itself. We discuss the
consequences for various X-ray emission models.Comment: 9 pages, 4 figures, to appear in MNRA
SAWA experiment ? properties of mineral dust aerosol as seen by synergic lidar and sun-photometer measurements
International audienceWe propose a method of retrieving basic information on mineral dust aerosol particles from synergic sun-photometer and multi-wavelength lidar measurements as well as from the observations of lidar light depolarisation. We use this method in a case study of mineral dust episode in Central Europe. Lidar signals are inversed with a modified Klett-Fernald algorithm. Aerosol optical depth measured with the sun-photometer allows to reduce uncertainties in the inversion procedure through which we estimate vertical profile of aerosol extinction. Next we assume that aerosol particles may be represented by ensemble of randomly oriented, identical spheroids. Having calculated vertical profiles of aerosol extinction coefficients for lidar wavelengths, we compute the profiles of local Angstrom exponent. We use laser beam depolarisation together with the calculated Angstrom exponents to estimate the shapes (aspect ratios) and sizes of the spheroids. Numerical calculations are performed with the transition matrix (T-matrix) algorithm by M. Mishchenko. The proposed method was first used during SAWA measurement campaign in Warsaw, spring 2005, to characterise the particles of desert dust, drifting over Poland with a southern-eastern wind (13?14 April). Observations and T-matrix calculations show that mode radii of spheroids representative for desert aerosols' particles are in the range of 0.15?0.3 ?m, while their aspect ratios are lower than 0.7 or larger than 1.7
Hidden symmetries in the asymmetric exclusion process
We present a spectral study of the evolution matrix of the totally asymmetric
exclusion process on a ring at half filling. The natural symmetries
(translation, charge conjugation combined with reflection) predict only two
fold degeneracies. However, we have found that degeneracies of higher order
also exist and, as the system size increases, higher and higher orders appear.
These degeneracies become generic in the limit of very large systems. This
behaviour can be explained by the Bethe Ansatz and suggests the presence of
hidden symmetries in the model.
Keywords: ASEP, Markov matrix, symmetries, spectral degeneracies, Bethe
Ansatz.Comment: 16 page
<i>Spitzer</i> microlens measurement of a massive remnant in a well-separated binary
We report the detection and mass measurement of a binary lens OGLE-2015-BLG-1285La,b, with the more massive component having M1 > 1.35 M⊙ (80% probability). A main-sequence star in this mass range is ruled out by limits on blue light, meaning that a primary in this mass range must be a neutron star (NS) or black hole (BH). The system has a projected separation r⊥ = 6.1 ± 0.4 AU and lies in the Galactic bulge. These measurements are based on the "microlens parallax" effect, i.e., comparing the microlensing light curve as seen from Spitzer, which lay at 1.25 AU projected from Earth, to the light curves from four ground-based surveys, three in the optical and one in the near-infrared. Future adaptive optics imaging of the companion by 30 m class telescopes will yield a much more accurate measurement of the primary mass. This discovery both opens the path and defines the challenges to detecting and characterizing BHs and NSs in wide binaries, with either dark or luminous companions. In particular, we discuss lessons that can be applied to future Spitzer and Kepler K2 microlensing parallax observations
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