18,050 research outputs found
Novel techniques in VUV high-resolution spectroscopy
Novel VUV sources and techniques for VUV spectroscopy are reviewed.
Laser-based VUV sources have been developed via non-linear upconversion of
laser pulses in the nanosecond (ns), the picosecond (ps), and femtosecond (fs)
domain, and are applied in high-resolution gas phase spectroscopic studies.
While the ns and ps pulsed laser sources, at Fourier-transform limited
bandwidths, are used in wavelength scanning spectroscopy, the fs laser source
is used in a two-pulse time delayed mode. In addition a Fourier-transform
spectrometer for high resolution gas-phase spectroscopic studies in the VUV is
described, exhibiting the multiplex advantage to measure many resonances
simultaneously.Comment: 17 Pages, 8 figures, Conference proceedings of the VUV/X-ray 2013 at
Hefei, Chin
Symmetry breaking effects upon bipartite and multipartite entanglement in the XY model
We analyze the bipartite and multipartite entanglement for the ground state
of the one-dimensional XY model in a transverse magnetic field in the
thermodynamical limit. We explicitly take into account the spontaneous symmetry
breaking in order to explore the relation between entanglement and quantum
phase transitions. As a result we show that while both bipartite and
multipartite entanglement can be enhanced by spontaneous symmetry breaking deep
into the ferromagnetic phase, only the latter is affected by it in the vicinity
of the critical point. This result adds to the evidence that multipartite, and
not bipartite, entanglement is the fundamental indicator of long range
correlations in quantum phase transitions.Comment: 13 pages, 19 figures, comments welcome. V2: small changes, published
versio
Cumulants of the three state Potts model and of nonequilibrium models with C3v symmetry
The critical behavior of two-dimensional stochastic lattice gas models with
C3v symmetry is analyzed. We study the cumulants of the order parameter for the
three state (equilibrium) Potts model and for two irreversible models whose
dynamic rules are invariant under the symmetry operations of the point group
C3v. By means of extensive numerical analysis of the phase transition we show
that irreversibility does not affect the critical behavior of the systems. In
particular we find that the Binder reduced fourth order cumulant takes a
universal value U* which is the same for the three state Potts model and for
the irreversible models. The same universal behavior is observed for the
reduced third-order cumulant.Comment: gzipped tar file containing: 1 latex file + 6 eps figure
Diffusion in the Continuous-Imaginary-Time Quantum World-Line Monte Carlo Simulations with Extended Ensembles
The dynamics of samples in the continuous-imaginary-time quantum world-line
Monte Carlo simulations with extended ensembles are investigated. In the case
of a conventional flat ensemble on the one-dimensional quantum S=1 bi-quadratic
model, the asymmetric behavior of Monte Carlo samples appears in the diffusion
process in the space of the number of vertices. We prove that a local
diffusivity is asymptotically proportional to the number of vertices, and we
demonstrate the asymmetric behavior in the flat ensemble case. On the basis of
the asymptotic form, we propose the weight of an optimal ensemble as
, where denotes the number of vertices in a sample. It is shown
that the asymmetric behavior completely vanishes in the case of the proposed
ensemble on the one-dimensional quantum S=1 bi-quadratic model.Comment: 4 pages, 2 figures, update a referenc
Irreversible Opinion Spreading on Scale-Free Networks
We study the dynamical and critical behavior of a model for irreversible
opinion spreading on Barab\'asi-Albert (BA) scale-free networks by performing
extensive Monte Carlo simulations. The opinion spreading within an
inhomogeneous society is investigated by means of the magnetic Eden model, a
nonequilibrium kinetic model for the growth of binary mixtures in contact with
a thermal bath. The deposition dynamics, which is studied as a function of the
degree of the occupied sites, shows evidence for the leading role played by
hubs in the growth process. Systems of finite size grow either ordered or
disordered, depending on the temperature. By means of standard finite-size
scaling procedures, the effective order-disorder phase transitions are found to
persist in the thermodynamic limit. This critical behavior, however, is absent
in related equilibrium spin systems such as the Ising model on BA scale-free
networks, which in the thermodynamic limit only displays a ferromagnetic phase.
The dependence of these results on the degree exponent is also discussed for
the case of uncorrelated scale-free networks.Comment: 9 pages, 10 figures; added results and discussion on uncorrelated
scale-free networks; added references. To appear in PR
Scattering and self-adjoint extensions of the Aharonov-Bohm hamiltonian
We consider the hamiltonian operator associated with planar sec- tions of
infinitely long cylindrical solenoids and with a homogeneous magnetic field in
their interior. First, in the Sobolev space , we characterize all
generalized boundary conditions on the solenoid bor- der compatible with
quantum mechanics, i.e., the boundary conditions so that the corresponding
hamiltonian operators are self-adjoint. Then we study and compare the
scattering of the most usual boundary con- ditions, that is, Dirichlet, Neumann
and Robin.Comment: 40 pages, 5 figure
Comportamento de variedades de aipim no estado de Sergipe.
Dez variedades de aipim foram avaliadas quanto à produção de parte aérea, de raízes e teores de matéria seca e de amido, em diferentes épocas de colheita, em três microrregiões do estado de Sergipe, no período de 2004 a 2006, visando à recomendação daquelas mais promissoras para cultivo nessas regiões.bitstream/CPATC/19760/1/bp-20.pd
The finiteness of the four dimensional antisymmetric tensor field model in a curved background
A renormalizable rigid supersymmetry for the four dimensional antisymmetric
tensor field model in a curved space-time background is constructed. A closed
algebra between the BRS and the supersymmetry operators is only realizable if
the vector parameter of the supersymmetry is a covariantly constant vector
field. This also guarantees that the corresponding transformations lead to a
genuine symmetry of the model. The proof of the ultraviolet finiteness to all
orders of perturbation theory is performed in a pure algebraic manner by using
the rigid supersymmetry.Comment: 23 page
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