808,887 research outputs found
Kondo screening suppression by spin-orbit interaction in quantum dots
We study the transport properties of a quantum dot embedded in an
Aharonov-Bohm ring in the presence of spin-orbit interactions. Using a
numerical renormalization group analysis of the system in the Kondo regime, we
find that the competition of Aharonov-Bohm and spin-orbit dynamical phases
induces a strong suppression of the Kondo state singlet, somewhat akin to an
effective intrinsic magnetic field in the system. This effective field breaks
the spin degeneracy of the localized state and produces a finite magnetic
moment in the dot. By introducing an {\em in-plane} Zeeman field we show that
the Kondo resonance can be fully restored, reestablishing the spin singlet and
a desired spin filtering behavior in the Kondo regime, which may result in full
spin polarization of the current through the ring.Comment: 4 pages, 4 figure
Saturation and Critical Phenomena in DIS
It is argued that the expected turn-down in of the cross sections
(structure functions ), assumed to result from the saturation of
parton densities in the nucleon, is related to a phase transition from the
(almost) ideal partonic gas, obeying Bjorken scaling, to a partonic "liquid".
This can be quantified in the framework of statistical models, percolation and
other approaches to collective phenomena of the strongly interacting matter.
Similarities and differences between the case of lepton-hadron, hadron-hadron
and nuclear collisions are discussed.Comment: 7 pages, 2 figures, talk given by L.L. Jenkovszky at the EDS'09
Conferenc
Viable f(T) models are practically indistinguishable from LCDM
We investigate the cosmological predictions of several models, with up
to two parameters, at both the background and the perturbation levels. Using
current cosmological observations (geometric supernovae type Ia, cosmic
microwave background and baryonic acoustic oscillation and dynamical growth
data) we impose constraints on the distortion parameter, which quantifies the
deviation of these models from the concordance cosmology at the
background level. In addition we constrain the growth index predicted
in the context of these models using the latest perturbation growth data in the
context of three parametrizations for . The evolution of the best fit
effective Newton constant, which incorporates the -gravity effects, is
also obtained along with the corresponding error regions. We show
that all the viable parameter sectors of the gravity models considered
practically reduce these models to CDM. Thus, the degrees of freedom
that open up to CDM in the context of gravity models are not
utilized by the cosmological data leading to an overall disfavor of these
models.Comment: 16 pages, 9 figures, changes match published versio
Analytic Solution for the Ground State Energy of the Extensive Many-Body Problem
A closed form expression for the ground state energy density of the general
extensive many-body problem is given in terms of the Lanczos tri-diagonal form
of the Hamiltonian. Given the general expressions of the diagonal and
off-diagonal elements of the Hamiltonian Lanczos matrix, and
, asymptotic forms and can be defined in
terms of a new parameter ( is the Lanczos iteration and is
the size of the system). By application of theorems on the zeros of orthogonal
polynomials we find the ground-state energy density in the bulk limit to be
given in general by .Comment: 10 pages REVTex3.0, 3 PS figure
Theoretical backgrounds of durability analysis by normalized equivalent stress functionals
Generalized durability diagrams and their properties are considered for a material under a multiaxial loading given by an arbitrary function of time. Material strength and durability under such loading are described in terms of durability, safety factor and normalized equivalent stress. Relations between these functionals are analysed. We discuss some material properties including time and load stability, self-degradation (ageing), and monotonic damaging. Phenomenological strength conditions are presented in terms of the normalized equivalent stress. It is shown that the damage based durability analysis is reduced to a particular case of such strength conditions. Examples of the reduction are presented for some known durability models. The approach is applicable to the strength and durability description at creep and impact loading and their combination
Comment on "Acoustics of tachyon Fermi gas" [E. Trojan and G.V. Vlasov, arXiv:1103.2276 (hep-ph)]
In contrast to Trojan and Vlasov [arXiv:1103.2276 (hep-ph)], it is found that
an ideal Fermi gas of tachyons has a subluminous velocity of sound for any
particle density and, therefore, the causality condition for a tachyon gas
holds always true. Also, an ideal Fermi gas of tachyons never possesses an
exotic equation of state with the pressure exceeding the energy density.Comment: 1 page + Ref
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