10,259 research outputs found
Density functional theory of superconductivity in doped tungsten oxides
We apply density functional theory for superconductors (SCDFT) to doped tungsten oxide in three forms: electrostatically doped WO3, perovskite WO3−xFx, and hexagonal CsxWO3. We achieve a consistent picture in which the experimental superconducting transition temperature Tc is reproduced, and superconductivity is understood as a weak-coupling state sustained by soft vibrational modes of the WO6 octahedra. SCDFT simulations of CsxWO3 allow us to explain the anomalous Tc behavior observed in most tungsten bronzes, where Tc decreases with increasing carrier density. Here, the opening of structural channels to host Cs atoms induces a softening of strongly coupled W-O modes. By increasing the Cs content, these modes are screened and Tc is strongly reduced
Stochastic Schr\"odinger equations with coloured noise
A natural non-Markovian extension of the theory of white noise quantum
trajectories is presented. In order to introduce memory effects in the
formalism an Ornstein-Uhlenbeck coloured noise is considered as the output
driving process. Under certain conditions a random Hamiltonian evolution is
recovered. Moreover, non-Markovian stochastic Schr\"odinger equations which
unravel non-Markovian master equations are derived.Comment: 4pages, revte
Star formation in early-type galaxies: the role of stellar winds and kinematics
Early-type galaxies (ETGs) host a hot ISM produced mainly by stellar winds,
and heated by Type Ia supernovae and the thermalization of stellar motions.
High resolution 2D hydrodynamical simulations showed that ordered rotation in
the stellar component results in the formation of a centrifugally supported
cold equatorial disc. In a recent numerical investigation we found that
subsequent generations of stars are formed in this cold disc; this process
consumes most of the cold gas, leaving at the present epoch cold masses
comparable to those observed. Most of the new stellar mass formed a few Gyrs
ago, and resides in a disc.Comment: 2 pages, 1 figure, to appear in proceedings of IAU Symposium 315,
"From Interstellar Clouds to Star-Forming Galaxies: Universal Processes?", P.
Jablonka, F. Van der Tak & P. Andre', ed
On the (2,3)-generation of the finite symplectic groups
This paper is a new important step towards the complete classification of the
finite simple groups which are -generated. In fact, we prove that the
symplectic groups are -generated for all . Because
of the existing literature, this result implies that the groups
are -generated for all , with the exception of and
More on regular subgroups of the affine group
This paper is a new contribution to the study of regular subgroups of the
affine group , for any field . In particular we associate to any
partition of abelian regular subgroups in such a
way that different partitions define non-conjugate subgroups. Moreover, we
classify the regular subgroups of certain natural types for . Our
classification is equivalent to the classification of split local algebras of
dimension over . Our methods, based on classical results of linear
algebra, are computer free
The simple classical groups of dimension less than 6 which are (2,3)-generated
In this paper we determine the classical simple groups of dimension r=3,5
which are (2,3)-generated (the cases r = 2, 4 are known). If r = 3, they are
PSL_3(q), q 4, and PSU_3(q^2), q^2 9, 25. If r = 5 they are PSL_5(q), for
all q, and PSU_5(q^2), q^2 >= 9. Also, the soluble group PSU_3(4) is not
(2,3)-generated. We give explicit (2,3)-generators of the linear preimages, in
the special linear groups, of the (2,3)-generated simple groups.Comment: 12 page
The -generation of the finite unitary groups
In this paper we prove that the unitary groups are
-generated for any prime power and any integer . By
previous results this implies that, if , the groups and
are -generated, except when
.Comment: In this version, we obtained a complete classification of the finite
simple unitary groups which are (2,3)-generated; some proofs have been
semplifie
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