1,701 research outputs found

### Bose-Einstein-condensed gases with arbitrary strong interactions

Bose-condensed gases are considered with an effective interaction strength
varying in the whole range of the values between zero and infinity. The
consideration is based on the usage of a representative statistical ensemble
for Bose systems with broken global gauge symmetry. Practical calculations are
illustrated for a uniform Bose gas at zero temperature, employing a
self-consistent mean-field theory, which is both conserving and gapless.Comment: Latex file, 23 pages, 4 figure

### Non-perturbative solutions in the electro-weak theory with $\bar t t$ condensate and the $t$-quark mass

We apply Bogoliubov compensation principle to the gauge electro-weak
interaction to demonstrate a spontaneous generation of anomalous three-boson
gauge invariant effective interaction. The non-trivial solution of compensation
equations uniquely defines the form-factor of the anomalous interaction and
parameters of the theory including value of gauge electro-weak coupling
$g(M_W^2)$ in satisfactory agreement with its experimental value. A possibility
of spontaneous generation of effective four-fermion interaction of heavy quarks
is also demonstrated. This interaction defines an equation for a scalar bound
state of heavy quarks which serve as a substitute for the elementary scalar
Higgs doublet. As a result we calculate the $t$-quark mass $m_t\,=\,177\,GeV$
in satisfactory agreement with the experimental value. The results strongly
support idea of $\bar t\,t$ condensate as a source of the electro-weak symmetry
breaking.Comment: 16 pages, 5 figures. arXiv admin note: substantial overlap with
arXiv:1103.395

### CDF Wjj anomaly as a non-perturbative effect of the electro-weak interaction

The recently reported CDF excess at $120\,-\, 160\,GeV$ in invariant mass
distribution of jet pairs accompanying $W$-boson is tentatively interpreted as
a bound state of two $W$ decaying to quark-anti-quark pair. Non-perturbative
effects of EW interaction obtained by application of Bogoliubov compensation
approach lead to such bound state due to existence of anomalous three-boson
gauge-invariant effective interaction. The application of this scheme gives
satisfactory agreement with existing data without any adjusting parameter but
the bound state mass $145\,GeV$.Comment: 5 pages, 2 figure

### Finite temperature effects in light scattering off Cooper-paired Fermi atoms

We study stimulated light scattering off a superfluid Fermi gas of atoms at
finite temperature. We derive response function that takes into account vertex
correction due to final state interactions; and analyze finite temperature
effects on collective and quasiparticle excitations of a uniform superfluid
Fermi gas. Light polarization is shown to play an important role in
excitations. Our results suggest that it is possible to excite
Bogoliubov-Anderson phonon at a large scattering length by light scattering.Comment: 18 pages, 4 figures, Accepted in J. Phys. B: At. Mol. & Opt. Phy

### Gapless Hartree-Fock-Bogoliubov Approximation for Bose Gases

A dilute Bose system with Bose-Einstein condensate is considered. It is shown
that the Hartree-Fock-Bogolubov approximation can be made both conserving as
well as gapless. This is achieved by taking into account all physical
normalization conditions, that is, the normalization condition for the
condensed particles and that for the total number of particles. Two Lagrange
multipliers, introduced for preserving these normalization conditions, make the
consideration completely self-consistent.Comment: Latex file, 22 pages, 2 figure

### Microscopic calculation of 240Pu scission with a finite-range effective force

Hartree-Fock-Bogoliubov calculations of hot fission in $^{240}\textrm{Pu}$
have been performed with a newly-implemented code that uses the D1S
finite-range effective interaction. The hot-scission line is identified in the
quadrupole-octupole-moment coordinate space. Fission-fragment shapes are
extracted from the calculations. A benchmark calculation for
$^{226}\textrm{Th}$ is obtained and compared to results in the literature. In
addition, technical aspects of the use of HFB calculations for fission studies
are examined in detail. In particular, the identification of scission
configurations, the sensitivity of near-scission calculations to the choice of
collective coordinates in the HFB iterations, and the formalism for the
adjustment of collective-variable constraints are discussed. The power of the
constraint-adjustment algorithm is illustrated with calculations near the
critical scission configurations with up to seven simultaneous constraints.Comment: 18 pages, 24 figures, to be published in Physical Review

### Stability of quasi-two-dimensional Bose-Einstein condensates with dominant dipole-dipole interactions

We consider quasi-two-dimensional atomic/molecular Bose-Einstein condensates
with both contact and dipole-dipole interactions. It is shown that, as a
consequence of the dimensional reduction, and within mean-field theory, the
condensates do not develop unstable excitation spectra, even when the
dipole-dipole interaction completely dominates the contact interaction.Comment: 4 pages of RevTex4, 3 figures; Rapid Communication in Physical Review
A (to be published

### Coupling running through the Looking-Glass of dimensional Reduction

The dimensional reduction, in a form of transition from four to two
dimensions, was used in the 90s in a context of HE Regge scattering. Recently,
it got a new impetus in quantum gravity where it opens the way to
renormalizability and finite short-distance behavior. We consider a QFT model
$g\,\varphi^4\,$ with running coupling defined in both the two domains of
different dimensionality; the \gbar(Q^2)\, evolutions being duly conjugated
at the reduction scale $\,Q\sim M.$ Beyond this scale, in the deep UV 2-dim
region, the running coupling does not increase any more. Instead, it {\it
slightly decreases} and tends to a finite value \gbar_2(\infty) \,< \,
\gbar_2(M^2)\, from above. As a result, the global evolution picture looks
quite peculiar and can propose a base for the modified scenario of gauge
couplings behavior with UV fixed points provided by dimensional reduction
instead of leptoquarks.Comment: 8 pages, 4 figures,Version to match the one which (besides the
Appendix) will appear in "Particles and Nuclei (PEPAN), Letters", v.7, No
6(162) 2010 pp 625-631. Slightly edited, one more reference and related
numerical estimate adde

### Nonequilibrium Fock space for the electron transport problem

Based on the formalism of thermo field dynamics we propose a concept of
nonequilibrium Fock space and nonequilibrium quasiparticles for quantum
many-body system in nonequilibrium steady state. We develop a general theory as
well as demonstrate the utility of the approach on the example of electron
transport through the interacting region. The proposed approach is compatible
with advanced methods of electronic structure calculations such as coupled
cluster theory and configuration interaction

### Subgap features due to quasiparticle tunneling in quantum dots coupled to superconducting leads

We present a microscopic theory of transport through quantum dot set-ups
coupled to superconducting leads. We derive a master equation for the reduced
density matrix to lowest order in the tunneling Hamiltonian and focus on
quasiparticle tunneling. For high enough temperatures transport occurs in the
subgap region due to thermally excited quasiparticles, which can be used to
observe excited states of the system for low bias voltages. On the example of a
double quantum dot we show how subgap transport spectroscopy can be done.
Moreover, we use the single level quantum dot coupled to a normal and a
superconducting lead to give a possible explanation for the subgap features
observed in the experiments published in Appl. Phys. Lett. 95, 192103 (2009).Comment: 18 pages, 20 figures, revised according to published versio

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