4,901 research outputs found
Complexity in parametric Bose-Hubbard Hamiltonians and structural analysis of eigenstates
We consider a family of chaotic Bose-Hubbard Hamiltonians (BHH) parameterized
by the coupling strength between neighboring sites. As increases the
eigenstates undergo changes, reflected in the structure of the Local Density of
States. We analyze these changes, both numerically and analytically, using
perturbative and semiclassical methods. Although our focus is on the quantum
trimer, the presented methodology is applicable for the analysis of longer
lattices as well.Comment: 4 pages, 4 figure
Sonoluminescence as Quantum Vaccum Radiation
We argue that the available experimental data is not compatible with models
of sonoluminescence which invoke dynamical properties of the interface without
regard to the compositional properties of the trapped gas inside the bubble.Comment: 2 pages,Revtex,No figures,Submitted to PRL(comments
Controlled quantum stirring of Bose-Einstein condensates
By cyclic adiabatic change of two control parameters of an optical trap one
can induce a circulating current of condensed bosons. The amount of particles
that are transported per period depends on the "radius" of the cycle, and this
dependence can be utilized in order to probe the interatomic interactions. For
strong repulsive interaction the current can be regarded as arising from a
sequence of Landau-Zener crossings. For weaker interaction one observes either
gradual or coherent mega crossings, while for attractive interaction the
particles are glued together and behave like a classical ball. For the analysis
we use the Kubo approach to quantum pumping with the associated Dirac monopoles
picture of parameter space.Comment: 12 pages, 8 figure
Chiral transition in a magnetic field and at finite baryon density
We consider the quark-meson model with two quark flavors in a constant
external magnetic field at finite temperature and finite baryon
chemical potential . We calculate the full renormalized effective
potential to one-loop order in perturbation theory. We study the system in the
large- limit, where we treat the bosonic modes at tree level. It is shown
that the system exhibits dynamical chiral symmetry breaking, i. e. that an
arbitrarily weak magnetic field breaks chiral symmetry dynamically, in
agreement with earlier calculations using the NJL model. We study the influence
on the phase transition of the fermionic vacuum fluctuations. For strong
magnetic fields, and in the chiral limit, the transition
is first order in the entire plane if vacuum fluctuations are not
included and second order if they are included. At the physical point, the
transition is a crossover for with and without vacuum fluctuations.Comment: 11 pages. 5figs. V2: fixed a few typos and added refs. Submitted to
PRD. V3: Added refs and substantial revision of tex
Spectrum of Higgsonium in the SM and beyond
Using the formalism of Bethe-Salpeter equation (BSE) the Higgsonium bound
state is studied. The condition for formation of Higgsonium bound states are
discussed in SM and in the simple extension of.Comment: 7 pages, talk presented at SCADRON 70, Workshop on Scalar Mesons and
Related Topics, February 2008, Lisbo
Mesons and tachyons with confinement and chiral restoration, and NA60
In this paper the spectrum of quark-antiquark systems, including light mesons
and tachyons, is studied in the true vacuum and in the chiral invariant vacuum.
The mass gap equation for the vacua and the Salpeter-RPA equation for the
mesons are solved for a simple chiral invariant and confining quark model. At
T=0 and in the true vacuum, the scalar and pseudoscalar, or the vector and
axial vector are not degenerate, and in the chiral limit, the pseudoscalar
groundstates are Goldstone bosons. At T=0 the chiral invariant vacuum is an
unstable vacuum, decaying through an infinite number of scalar and pseudoscalar
tachyons. Nevertheless the axialvector and vector remain mesons, with real
masses. To illustrate the chiral restoration, an arbitrary path between the two
vacua is also studied. Different families of light-light and heavy-light
mesons, sensitive to chiral restoration, are also studied. At higher
temperatures the potential must be suppressed, and the chiral symmetry can be
restored without tachyons, but then all mesons have small real masses.
Implications for heavy-ion collisions, in particular for the recent vector
meson spectra measured by the NA60 collaboration, are discussed.Comment: 9 pages, 5 figures, 3 table
Nucleon resonance contributions to unpolarised inclusive electron scattering
The first CLAS12 experiments will provide high-precision data on inclusive
electron scattering observables at a photon virtuality ranging from 0.05
GeV to 12 GeV and center-of-mass energies up to 4 GeV. In view of
this endeavour, we present the modeling of the resonant contributions to the
inclusive electron scattering observables. As input, we use the existing CLAS
electrocoupling results obtained from exclusive meson electroproduction data
off protons, and evaluate for the first time the resonant contributions based
on the experimental results on the nucleon resonance electroexcitation. The
uncertainties are given by the data and duly propagated through a Monte Carlo
approach. In this way, we obtain estimates for the resonant contributions,
important for insight into the nucleon parton distributions in the resonance
region and for the studies of quark-hadron duality
Polarized proton structure in the resonance region
In view of the precise data available on inclusive polarized electron
scattering off polarized proton targets in the nucleon resonance excitation
region, we compare these results with the coherent sum of resonant
contributions to the polarized structure function and virtual photon
asymmetry . To this goal, we employ the nucleon resonance
electroexcitation amplitudes determined for photon virtualities 5.0
GeV from analyses of the CLAS data on exclusive electroproduction off
protons in the resonance region. Most of the well established resonances of
four star PDG status in the mass range up to 1.75~GeV are included. We find
that the resonance-like structures observed in the inclusive data are
related to the resonant contributions in the entire range of photon virtuality
where the data on are available. In the range of invariant mass of
the final hadron system 1.5 GeV, the data on the asymmetry are
well reproduced even when accounting for resonant contributions only,
especially for the larger values of and energies analysed. This
observation offers an interesting hint to quark-hadron duality seen in
polarized inclusive electron scattering observables.Comment: Contribution to proceedings: Emergence and Structure of Baryons -
Selected Contributions from the International Conference Baryons 202
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