2,829 research outputs found
On the chemical equilibration of strangeness-exchange reaction in heavy-ion collisions
The strangeness-exchange reaction pi + Y -> K- + N is shown to be the
dynamical origin of chemical equilibration for K- production in heavy-ion
collisions up to beam energies of 10 A GeV. The hyperons occurring in this
process are produced associately with K+ in baryon-baryon and meson-baryon
interactions. This connection is demonstrated by the ratio K-/K+ which does not
vary with centrality and shows a linear correlation with the yield of pions per
participant. At incident energies above AGS this correlation no longer holds
due to the change in the production mechanism of kaons.Comment: 9 pages, 4 figure
Fast computation of the Kohn-Sham susceptibility of large systems
For hybrid systems, such as molecules grafted onto solid surfaces, the
calculation of linear response in time dependent density functional theory is
slowed down by the need to calculate, in N^4 operations, the susceptibility of
N non interacting Kohn-Sham reference electrons. We show how this
susceptibility can be calculated N times faster within finite precision. By
itself or in combination with previous methods, this should facilitate the
calculation of TDDFT response and optical spectra of hybrid systems.Comment: submitted 25/1/200
Self-consistent Green function approach for calculations of electronic structure in transition metals
We present an approach for self-consistent calculations of the many-body
Green function in transition metals. The distinguishing feature of our approach
is the use of the one-site approximation and the self-consistent quasiparticle
wave function basis set, obtained from the solution of the Schrodinger equation
with a nonlocal potential. We analyze several sets of skeleton diagrams as
generating functionals for the Green function self-energy, including GW and
fluctuating exchange sets. Their relative contribution to the electronic
structure in 3d-metals was identified. Calculations for Fe and Ni revealed
stronger energy dependence of the effective interaction and self-energy of the
d-electrons near the Fermi level compared to s and p electron states.
Reasonable agreement with experimental results is obtained
Dirac Quantization of the Chern-Simons Field Theory in the Coulomb Gauge
In this letter the Chern-Simons field theories are studied in the Coulomb
gauge using the Dirac's canonical formalism for constrained systems. As a
strategy, we first work out the constraints and then quantize, replacing the
Dirac brackets with quantum commutators. We find that the Chern-Simons field
theories become two dimensional models with no propagation along the time
direction. Moreover, we prove that, despite of the presence of non-trivial
self-interactions in the gauge fixed functional, the commutation relations
between the fields are trivial at any order in perturbation theory in the
absence of couplings with matter fields. If these couplings are present,
instead, the commutation relations become rather involved, but it is still
possible to study their main properties and to show that they vanish at the
tree level.Comment: 15 pages, Latex+RevTex, no figure
Experimental realization of the Yang-Baxter Equation via NMR interferometry
The Yang-Baxter equation is an important tool in theoretical physics, with
many applications in different domains that span from condensed matter to
string theory. Recently, the interest on the equation has increased due to its
connection to quantum information processing. It has been shown that the
Yang-Baxter equation is closely related to quantum entanglement and quantum
computation. Therefore, owing to the broad relevance of this equation, besides
theoretical studies, it also became significant to pursue its experimental
implementation. Here, we show an experimental realization of the Yang-Baxter
equation and verify its validity through a Nuclear Magnetic Resonance (NMR)
interferometric setup. Our experiment was performed on a liquid state
Iodotrifluoroethylene sample which contains molecules with three qubits. We use
Controlled-transfer gates that allow us to build a pseudo-pure state from which
we are able to apply a quantum information protocol that implements the
Yang-Baxter equation.Comment: 10 pages and 6 figure
A planar extrapolation of the correlation problem that permits pairing
It was observed previously that an SU(N) extension of the Hubbard model is
dominated, at large N, by planar diagrams in the sense of 't Hooft, but the
possibility of superconducting pairing got lost in this extrapolation. To allow
for this possibility, we replace SU(N) by U(N,q), the unitary group in a vector
space of quaternions. At the level of the free energy, the difference between
the SU(N)and U(N,q) extrapolations appears only to first nonleading order in N.Comment: 8 pages, 2 figure
Integrable multiparametric quantum spin chains
Using Reshetikhin's construction for multiparametric quantum algebras we
obtain the associated multiparametric quantum spin chains. We show that under
certain restrictions these models can be mapped to quantum spin chains with
twisted boundary conditions. We illustrate how this general formalism applies
to construct multiparametric versions of the supersymmetric t-J and U models.Comment: 17 pages, RevTe
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