20,779 research outputs found
Light- and strange-quark mass dependence of the meson revisited
Recent lattice data on -scattering phase shifts in the
vector-isovector channel, pseudoscalar meson masses and decay constants for
strange-quark masses smaller or equal to the physical value allow us to study
the strangeness dependence of these observables for the first time. We perform
a global analysis on two kind of lattice trajectories depending on whether the
sum of quark masses or the strange-quark mass is kept fixed to the physical
point. The quark mass dependence of these observables is extracted from
unitarized coupled-channel one-loop Chiral Perturbation Theory. This analysis
guides new predictions on the meson properties over trajectories
where the strange-quark mass is lighter than the physical mass, as well as on
the SU(3) symmetric line. As a result, the light- and strange-quark mass
dependence of the meson parameters are discussed and precise values
of the Low Energy Constants present in unitarized one-loop Chiral Perturbation
Theory are given. Finally, the current discrepancy between two- and
three-flavor lattice results for the meson is studied.Comment: 44 pages, 41 figures, 11 table
Spectral statistics of molecular resonances in erbium isotopes: How chaotic are they?
We perform a comprehensive analysis of the spectral statistics of the
molecular resonances in Er and Er observed in recent ultracold
collision experiments [Frisch et al., Nature {\bf 507}, 475 (2014)] with the
aim of determining the chaoticity of this system. We calculate different
independent statistical properties to check their degree of agreement with
random matrix theory (RMT), and analyze if they are consistent with the
possibility of having missing resonances. The analysis of the short-range
fluctuations as a function of the magnetic field points to a steady increase of
chaoticity until G. The repulsion parameter decreases for higher
magnetic fields, an effect that can be interpreted as due to missing
resonances. The analysis of long-range fluctuations allows us to be more
quantitative and estimate a fraction of missing levels. Finally, a
study of the distribution of resonance widths provides additional evidence
supporting missing resonances of small width compared with the experimental
magnetic field resolution. We conclude that further measurements with increased
resolution will be necessary to give a final answer to the problem of missing
resonances and the agreement with RMT.Comment: 9 pages, 6 figure
Controlled localization of interacting bosons in a disordered optical lattice
We show that tunneling and localization properties of interacting ultracold
atoms in an optical lattice can be controlled by adiabatically turning on a
fast oscillatory force even in the presence of disorder. Our calculations are
based on the exact solution of the time-dependent Schroedinger equation, using
the Floquet formalism. Implications of our findings for larger systems and the
possibility of controlling the phase diagram of disordered-interacting bosonic
systems are discussed.Comment: 7 pages 7 fig
Length-dependent oscillations of the conductance through atomic chains: The importance of electronic correlations
We calculate the conductance of atomic chains as a function of their length.
Using the Density Matrix Renormalization Group algorithm for a many-body model
which takes into account electron-electron interactions and the shape of the
contacts between the chain and the leads, we show that length-dependent
oscillations of the conductance whose period depends on the electron density in
the chain can result from electron-electron scattering alone. The amplitude of
these oscillations can increase with the length of the chain, in contrast to
the result from approaches which neglect the interactions.Comment: 7 pages, 4 figure
Dispersive spherical optical model of neutron scattering from Al27 up to 250 MeV
A spherical optical model potential (OMP) containing a dispersive term is
used to fit the available experimental database of angular distribution and
total cross section data for n + Al27 covering the energy range 0.1- 250 MeV
using relativistic kinematics and a relativistic extension of the Schroedinger
equation. A dispersive OMP with parameters that show a smooth energy dependence
and energy independent geometry are determined from fits to the entire data
set. A very good overall agreement between experimental data and predictions is
achieved up to 150 MeV. Inclusion of nonlocality effects in the absorptive
volume potential allows to achieve an excellent agreement up to 250 MeV.Comment: 13 figures (11 eps and 2 jpg), 3 table
meson in dense matter
We study the properties of mesons in nuclear matter using a
unitary approach in coupled channels within the framework of the local hidden
gauge formalism and incorporating the decay channel in matter. The
in-medium interaction accounts for Pauli blocking effects and
incorporates the self-energy in a self-consistent manner. We also
obtain the (off-shell) spectral function and analyze its behaviour
at finite density and momentum. At normal nuclear matter density, the meson feels a moderately attractive potential while the width
becomes five times larger than in free space. We estimate the transparency
ratio of the reaction, which we propose as
a feasible scenario at present facilities to detect the changes of the
properties of the meson in the nuclear medium.Comment: 26 pages, 9 figures, one new section added, version published in
Phys. ReV. C, http://link.aps.org/doi/10.1103/PhysRevC.82.04521
Spin-wave amplification and lasing driven by inhomogeneous spin transfer torques
We show that an inhomogeneity in the spin-transfer torques in a metallic
ferromagnet under suitable conditions strongly amplifies incoming spin waves.
Moreover, at nonzero temperatures the incoming thermally occupied spin waves
will be amplified such that the region with inhomogeneous spin transfer torques
emits spin waves spontaneously, thus constituting a spin-wave laser. We
determine the spin-wave scattering amplitudes for a simplified model and
set-up, and show under which conditions the amplification and lasing occurs.
Our results are interpreted in terms of a so-called black-hole laser, and could
facilitate the field of magnonics, that aims to utilize spin waves in logic and
data-processing devices.Comment: 5 pages, 4 figure
A new interpretation for the and the prediction of novel exotic charmed mesons
In this manuscript we study the vector - vector interaction within the hidden
gauge formalism in a coupled channel unitary approach. In the sector
we get a pole in the T-matrix around MeV that we identify
with the , coupling strongly to the
(()) channels. In addition we obtain resonances in
other exotic sectors which have not been studied before such as ,
and . This 'flavor-exotic' states are interpreted as
, and molecular states but have not been
observed yet. In total we obtain nine states with different spin, isospin,
charm and strangeness of non and character, which have been
reported before
First clear evidence of quantum chaos in the bound states of an atomic nucleus
We study the spectral fluctuations of the Pb nucleus using the
complete experimental spectrum of 151 states up to excitation energies of
MeV recently identified at the Maier-Leibnitz-Laboratorium at Garching,
Germany. For natural parity states the results are very close to the
predictions of Random Matrix Theory (RMT) for the nearest-neighbor spacing
distribution. A quantitative estimate of the agreement is given by the Brody
parameter , which takes the value for regular systems and
for chaotic systems. We obtain which
is, to our knowledge, the closest value to chaos ever observed in experimental
bound states of nuclei. By contrast, the results for unnatural parity states
are far from RMT behavior. We interpret these results as a consequence of the
strength of the residual interaction in Pb, which, according to
experimental data, is much stronger for natural than for unnatural parity
states. In addition our results show that chaotic and non-chaotic nuclear
states coexist in the same energy region of the spectrum.Comment: 9 pages, 1 figur
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