6,220 research outputs found
Black-hole scattering with general spin directions from minimal-coupling amplitudes
We study the link between classical scattering of spinning black holes and quantum amplitudes for massive spin- particles. Generic spin orientations of the black holes are considered, allowing their spins to be deflected on par with their momenta. We re-derive the spin-exponentiated structure of the relevant tree-level amplitude from minimal coupling to Einstein's gravity, which in the limit generates the black holes' complete series of spin-induced multipoles. The resulting scattering function is seen to encode in a simple way the known net changes in the black-hole momenta and spins at first post-Minkowskian order. We connect our findings to a rigorous framework developed elsewhere for computing such observables from amplitudes
Surface Waves and Forced Oscillations in QHE Planar Samples
Dispersion relations and polarizations for surface waves in infinite planar
samples in the QHE regime are explicitly determined in the small wavevector
limit in which the dielectric tensor can be considered as local. The wavelength
and frequency regions of applicability of the results extends to the infrared
region for typical experimental conditions. Then, standard samples with
millimetric sizes seem to be able to support such excitations. Forced
oscillations are also determined which should be generated in the 2DEG by
external electromagnetic sources. They show an almost frequency independent
wavevelength which decreases with the magnetic field. A qualitative model based
in these solutions is also presented to describe a recently found new class of
resonances appearing near the edge of a 2DEG in the QHE regime.Comment: latex file, 18 pages, 3 figures, spelling correcte
Pseudoscalar pole light-by-light contributions to the muon in Resonance Chiral Theory
We have studied the transition form-factors
() within a chiral invariant framework that allows us to
relate the three form-factors and evaluate the corresponding contributions to
the muon anomalous magnetic moment , through pseudoscalar pole
contributions. We use a chiral invariant Lagrangian to describe the
interactions between the pseudo-Goldstones from the spontaneous chiral symmetry
breaking and the massive meson resonances. We will consider just the lightest
vector and pseudoscalar resonance multiplets. Photon interactions and flavor
breaking effects are accounted for in this covariant framework. This article
studies the most general corrections of order within this setting.
Requiring short-distance constraints fixes most of the parameters entering the
form-factors, consistent with previous determinations. The remaining ones are
obtained from a fit of these form-factors to experimental measurements in the
space-like () region of photon momenta. The combination of data,
chiral symmetry relations between form-factors and high-energy constraints
allows us to determine with improved precision the on-shell -pole
contribution to the Hadronic Light-by-Light scattering of the muon anomalous
magnetic moment: we obtain for
our best fit. This result was obtained excluding BaBar data, which our
analysis finds in conflict with the remaining experimental inputs. This study
also allows us to determine the parameters describing the system
in the two-mixing angle scheme and their correlations. Finally, a preliminary
rough estimate of the impact of loop corrections () and higher vector
multiplets (asym) enlarges the uncertainty up to .Comment: 43 pages, 5 figures. Accepted for publication in JHEP. New subsection
involving error analysis and some minor change
Helium- and Lithium-like ionic sequences: Critical charges
In non-relativistic quantum mechanics we study the Coulomb systems of
infinitely massive center of charge Z and two-three electrons: and
. It is shown that in both cases the total energy curve in is
smooth, without any visible irregularities. Thus, for both systems the physical
integer charges do not play a distinguished role as would be
associated with charge quantization. By definition, a critical charge
is a charge which separates a domain of the existence of bound states from a
domain of unbound ones (continuum). For both systems the critical charges are
found, and , respectively. Based on
numerical analysis, the Puiseux expansion in fractional powers of
is constructed for both systems. Our results indicate the existence of a
square-root branch point singularity at with exponent 3/2. A
connection between the critical charge and the radius of convergence of
1/Z-expansion is briefly discussed.Comment: 10 pages, LaTeX, typos corrected, Fig.1 added, a Note Added with
calculated critical charge for state for system,
$Z_{cr,2e}^{(2^1S)}\ =\ 1.02
Speeding up antidynamical Casimir effect with nonstationary qutrits
The antidynamical Casimir effect (ADCE) is a term coined to designate the
coherent annihilation of excitations due to resonant external perturbation of
system parameters, allowing for extraction of quantum work from nonvacuum
states of some field. Originally proposed for a two-level atom (qubit) coupled
to a single cavity mode in the context of nonstationary quantum Rabi model, it
suffered from very low transition rate and correspondingly narrow resonance
linewidth. In this paper we show analytically and numerically that the ADCE
rate can be increased by at least one order of magnitude by replacing the qubit
by an artificial three-level atom (qutrit) in a properly chosen configuration.
For the cavity thermal state we demonstrate that the dynamics of the average
photon number and atomic excitation is completely different from the qubit's
case, while the behavior of the total number of excitations is qualitatively
similar yet significantly faster.Comment: 9 pages, 4 figure
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