1,237 research outputs found
Search for evidence of two photon contribution in elastic electron proton data
We reanalyze the most recent data on elastic electron proton scattering. We
look for a deviation from linearity of the Rosenbluth fit to the differential
cross section, which would be the signature of the presence of two photon
exchange. The two photon contribution is parametrized by a one parameter
formula, based on symmetry arguments. The present data do not show evidence for
such deviation.Comment: 15 pages 3 figures More details on the fitting procedure, more
explicit explanation
Random matrices, non-backtracking walks, and orthogonal polynomials
Several well-known results from the random matrix theory, such as Wigner's
law and the Marchenko--Pastur law, can be interpreted (and proved) in terms of
non-backtracking walks on a certain graph. Orthogonal polynomials with respect
to the limiting spectral measure play a role in this approach.Comment: (more) minor change
Physics issues in simulations with dynamical overlap fermions
We discuss the impact of various improvements on simulations of dynamical
overlap fermions using the Hybrid Monte Carlo algorithm. We focus on the usage
of fat links and multiple pseudo-fermion fields.Comment: 14 pages, 10 figure
Strongly coupled large-angle stimulated Raman scattering of short laser pulses in plasma-filled capillaries
Strongly coupled large-angle stimulated Raman scattering (LA SRS) of a short
intense laser pulse proceeds in a plane plasma-filled capillary differently
than in a plasma with open boundaries. Oblique mirror reflections off capillary
walls partly suppress the lateral convection of scattered radiation and
increase the growth rate of the instability: the convective gain of the LA SRS
falls with an angle much slower than in an unbounded plasma and even for the
near-forward SRS can be close to that of the direct backscatter. The long-term
evolution of LA SRS in the interior of the capillary is dominated by
quasi-one-dimensional leaky modes, whose damping is related to the transmission
of electromagnetic waves through capillary walls.Comment: 11 pages, 6 figures; to be submitted to Physics of Plasma
Polarization effects in the reaction and determination of the meson form factors in the time--like region
The electron positron annihilation reaction into four pion production has
been studied, through the channel . The
differential (and total) cross sections and various polarization observables
for this reaction have been calculated in terms of the electromagnetic form
factors of the corresponding current. The elements of the
spin--density matrix of the meson were also calculated. Numerical
estimations have been done, with the help of phenomenological form factors
obtained in the space--like region of the momentum transfer squared and
analytically extended to the time-like region.Comment: 19 pages, 2 figures, to appear in Phys Rev
Radiative double electron capture by bare nucleus with emission of one photon
Calculation of the cross-section for the process of double electron capture
by bare nucleus with emission of a single photon is presented. The double
electron capture is evaluated within the framework of Quantum Electrodynamics
(QED). Line-Profile Approach (LPA) is employed. Since the radiative double
electron capture is governed by the electron correlation, corrections to the
interelectron interaction were calculated with high accuracy, partly to all
orders of the perturbation theory
Limiting Laws of Linear Eigenvalue Statistics for Unitary Invariant Matrix Models
We study the variance and the Laplace transform of the probability law of
linear eigenvalue statistics of unitary invariant Matrix Models of
n-dimentional Hermitian matrices as n tends to infinity. Assuming that the test
function of statistics is smooth enough and using the asymptotic formulas by
Deift et al for orthogonal polynomials with varying weights, we show first that
if the support of the Density of States of the model consists of two or more
intervals, then in the global regime the variance of statistics is a
quasiperiodic function of n generically in the potential, determining the
model. We show next that the exponent of the Laplace transform of the
probability law is not in general 1/2variance, as it should be if the Central
Limit Theorem would be valid, and we find the asymptotic form of the Laplace
transform of the probability law in certain cases
On the efficiency of Hamiltonian-based quantum computation for low-rank matrices
We present an extension of Adiabatic Quantum Computing (AQC) algorithm for
the unstructured search to the case when the number of marked items is unknown.
The algorithm maintains the optimal Grover speedup and includes a small
counting subroutine.
Our other results include a lower bound on the amount of time needed to
perform a general Hamiltonian-based quantum search, a lower bound on the
evolution time needed to perform a search that is valid in the presence of
control error and a generic upper bound on the minimum eigenvalue gap for
evolutions.
In particular, we demonstrate that quantum speedup for the unstructured
search using AQC type algorithms may only be achieved under very rigid control
precision requirements.Comment: 17 pages, no figures, to appear in JM
Analysis of polarization observables and radiative effects for the reaction
The expressions for the differential cross section and of the polarization
observables for the reaction are given in terms
of the nucleon electromagnetic form factors in the laboratory system. Radiative
corrections due to the emission of virtual and real soft photons from the
leptons are also calculated. Unlike the center-of- mass system case, they
depend on the scattering angle. Polarization effects are derived in the case
when the antiproton beam, the target and the electron in the final state are
polarized. Numerical estimations have been done for all observables for the
PANDA experimental conditions using models for the nucleon electromagnetic form
factors in the time-like region. The radiative corrections to the differential
cross section are calculated as function of the beam energy and of the electron
angle.Comment: 18 pages, 8 figure
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