1,434 research outputs found
How to reconcile the Rosenbluth and the polarization transfer method in the measurement of the proton form factors
The apparent discrepancy between the Rosenbluth and the polarization transfer
method for the ratio of the electric to magnetic proton form factors can be
explained by a two-photon exchange correction which does not destroy the
linearity of the Rosenbluth plot. Though intrinsically small, of the order of a
few percent of the cross section, this correction is kinematically enhanced in
the Rosenbluth method while it is small for the polarization transfer method,
at least in the range of (Q^2) where it has been used until now.Comment: 4 pages, 4 figures. Version accepted for publication in Phys. Rev.
Let
Superfluid states with moving condensate in nuclear matter
Superfluid states of symmetric nuclear matter with finite total momentum of
Cooper pairs (nuclear LOFF phase) are studied with the use of Fermi-liquid
theory in the model with Skyrme effective forces. It is considered the case of
four-fold splitting of the excitation spectrum due to finite superfluid
momentum and coupling of T=0 and T=1 pairing channels. It has been shown that
at zero temperature the energy gap in triplet-singlet (TS) pairing channel (in
spin and isospin spaces) for the SkM force demonstrates double-valued
behavior as a function of superfluid momentum. As a consequence, the phase
transition at the critical superfluid momentum from the LOFF phase to the
normal state will be of a first order. Behavior of the energy gap as a function
of density for TS pairing channel under increase of superfluid momentum changes
from one-valued to universal two-valued. It is shown that two-gap solutions,
describing superposition of states with singlet-triplet (ST) and TS pairing of
nucleons appear as a result of branching from one-gap ST solution. Comparison
of the free energies shows that the state with TS pairing of nucleons is
thermodynamically most preferable.Comment: Report on DAAD summer school "Dense matter in Particle- and
Astrophysics". Prepared with RevTeX4, 5p., 4 eps figure
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
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
Neutron electric form factor at large momentum transfer
Based on the recent, high precision data for elastic electron scattering from
protons and deuterons, at relatively large momentum transfer , we
determine the neutron electric form factor up to GeV. The values
obtained from the data (in the framework of the nonrelativistic impulse
approximation) are larger than commonly assumed and are in good agreement with
the Gari-Kr\"umpelmann parametrization of the nucleon electromagnetic form
factors.Comment: 11 pages 2 figure
Anisotropic multi-gap superfluid states in nuclear matter
It is shown that under changing density or temperature a nucleon Fermi
superfluid can undergo a phase transition to an anisotropic superfluid state,
characterized by nonvanishing gaps in pairing channels with singlet-singlet
(SS) and triplet-singlet (TS) pairing of nucleons (in spin and isospin spaces).
In the SS pairing channel nucleons are paired with nonzero orbital angular
momentum. Such two-gap states can arise as a result of branching from the
one-gap solution of the self-consistent equations, describing SS or TS pairing
of nucleons, that depends on the relationship between SS and TS coupling
constants at the branching point. The density/temperature dependence of the
order parameters and the critical temperature for transition to the anisotropic
two-gap state are determined in a model with the SkP effective interaction. It
is shown that the anisotropic SS-TS superfluid phase corresponds to a
metastable state in nuclear matter.Comment: Prepared with RevTeX4, 7p., 5 fi
Ultrarelativistic nanoplasmonics as a new route towards extreme intensity attosecond pulses
The generation of ultra-strong attosecond pulses through laser-plasma
interactions offers the opportunity to surpass the intensity of any known
laboratory radiation source, giving rise to new experimental possibilities,
such as quantum electrodynamical tests and matter probing at extremely short
scales. Here we demonstrate that a laser irradiated plasma surface can act as
an efficient converter from the femto- to the attosecond range, giving a
dramatic rise in pulse intensity. Although seemingly similar schemes have been
presented in the literature, the present setup deviates significantly from
previous attempts. We present a new model describing the nonlinear process of
relativistic laser-plasma interaction. This model, which is applicable to a
multitude of phenomena, is shown to be in excellent agreement with
particle-in-cell simulations. We provide, through our model, the necessary
details for an experiment to be performed. The possibility to reach intensities
above 10^26 W/cm^2, using upcoming 10 petawatt laser sources, is demonstrated.Comment: 15 pages, 5 figure
Competition of ferromagnetic and antiferromagnetic spin ordering in nuclear matter
In the framework of a Fermi liquid theory it is considered the possibility of
ferromagnetic and antiferromagnetic phase transitions in symmetric nuclear
matter with Skyrme effective interaction. The zero temperature dependence of
ferromagnetic and antiferromagnetic spin polarization parameters as functions
of density is found for SkM, SGII effective forces. It is shown that in the
density domain, where both type of solutions of self--consistent equations
exist, ferromagnetic spin state is more preferable than antiferromagnetic one.Comment: 9p., 3 figure
On the theory of magnetization in multiferroics: competition between ferro- and antiferromagnetic domains
Many technological applications of multiferroics are based on their ability
to reconstruct the domain structure (DS) under the action of small external
fields. In the present paper we analyze the different scenarios of the DS
behavior in a multiferroic that shows simultaneously ferro- and
antiferromagnetic ordering on the different systems of magnetic ions. We
consider the way to control a composition of the DS and macroscopic properties
of the sample by an appropriate field treatment. We found out that sensitivity
of the DS to the external magnetic field and the magnetic susceptibility in a
low-field region are determined mainly by the destressing effects (that have
magnetoelastic origin). In a particular case of SrCuOCl
crystal we anticipate the peculiarities of the elastic and magnetoelastic
properties at K.Comment: 16 pages, 10 figure
Reversibility conditions for quantum channels and their applications
A necessary condition for reversibility (sufficiency) of a quantum channel
with respect to complete families of states with bounded rank is obtained. A
full description (up to isometrical equivalence) of all quantum channels
reversible with respect to orthogonal and nonorthogonal complete families of
pure states is given. Some applications in quantum information theory are
considered.
The main results can be formulated in terms of the operator algebras theory
(as conditions for reversibility of channels between algebras of all bounded
operators).Comment: 28 pages, this version contains strengthened results of the previous
one and of arXiv:1106.3297; to appear in Sbornik: Mathematics, 204:7 (2013
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