7,628 research outputs found
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
Influence of estimated training status on anti and pro-oxidant activity, nitrite concentration, and blood pressure in middle-aged and older women
The purpose of this study was to compare the association between anti and pro-oxidant activity, nitrite concentration, and blood pressure (BP) in middle-aged and older women with different levels of estimated training status (TS). The sample consisted of 155 females (50-84 years) who were submitted to a physical examination to evaluate estimated TS through the "Functional Fitness Battery Test," BP measurements, and plasma blood samples to evaluate pro-oxidant and antioxidant activity and nitrite concentrations. Participants were separated by age into a middle-aged group (< 65 years) and an older (≥65 years) group and then subdivided in each group according to TS. Blood biochemistry was similar between groups. On the other hand, protein oxidation was lower in participants with higher TS, independent of age. Older females with higher TS presented higher nitrite concentrations, lower lipoperoxidation, and lower values of BP compared with those with lower TS. Lower GPx activity was observed in participants with higher TS compared with middle-aged with lower TS. Thus, our results suggest that good levels of TS may be associated with lower oxidative stress and higher nitrite concentration and may contribute to maintain normal or reduced blood pressure values.Fil: Jacomini, André M.. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Dias, Danielle da Silva. Universidade Nove de Julho; BrasilFil: Brito, Janaina de Oliveira. Universidade Nove de Julho; BrasilFil: da Silva, Roberta F.. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Monteiro, Henrique L.. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Llesuy, Susana Francisca. Universidade Nove de Julho; Brasil. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Bioquímica y Medicina Molecular. Universidad de Buenos Aires. Facultad Medicina. Instituto de Bioquímica y Medicina Molecular; ArgentinaFil: De Angelis, Kátia. Universidade Nove de Julho; BrasilFil: Amaral, Sandra L.. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Zago, Anderson S.. Universidade Estadual Paulista Julio de Mesquita Filho; Brasi
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
Glassy states in lattice models with many coexisting crystalline phases
We study the emergence of glassy states after a sudden cooling in lattice
models with short range interactions and without any a priori quenched
disorder. The glassy state emerges whenever the equilibrium model possesses a
sufficient number of coexisting crystalline phases at low temperatures,
provided the thermodynamic limit be taken before the infinite time limit. This
result is obtained through simulations of the time relaxation of the standard
Potts model and some exclusion models equipped with a local stochastic dynamics
on a square lattice.Comment: 12 pages, 4 figure
Fractal geometry of spin-glass models
Stability and diversity are two key properties that living entities share
with spin glasses, where they are manifested through the breaking of the phase
space into many valleys or local minima connected by saddle points. The
topology of the phase space can be conveniently condensed into a tree
structure, akin to the biological phylogenetic trees, whose tips are the local
minima and internal nodes are the lowest-energy saddles connecting those
minima. For the infinite-range Ising spin glass with p-spin interactions, we
show that the average size-frequency distribution of saddles obeys a power law
, where w=w(s) is the number of minima that can be
connected through saddle s, and D is the fractal dimension of the phase space
Two formation channels of UCDs in Hickson Compact Groups
The formation of ultra-compact dwarf galaxies (UCDs) is believed to be
interaction driven, and UCDs are abundant in the cores of galaxy clusters,
environments that mark the end-point of galaxy evolution. Nothing is known
about the properties of UCDs in compact groups of galaxies, environments where
most of galaxy evolution and interaction is believed to occur and where UCDs in
intermediate state of evolution may be expected. The main goal of this study is
to detect and characterize, for the first time, the UCD population of compact
groups. For that, 2 groups in different evolutionary stages, HCG 22 and HCG 90,
were targeted with VLT/FORS2/MXU. We detect 16 and 5 objects belonging to HCG
22 and HCG 90, respectively, covering the magnitude range -10.0 > M_R > -11.5
mag. Their colours are consistent with old ages covering a broad range in
metallicities. Photometric mass estimates put 4 objects in HCG 90 and 9 in HCG
22 in the mass range of UCDs (>2x10^6 M_Sun) for an assumed age of 12 Gyr.
These UCDs are on average 2-3 times larger than typical Galactic GCs, covering
a range of 2 >~ r_h >~ 21 pc. The UCDs in HCG 22 are more concentrated around
the central galaxy than in HCG 90, at the 99% confidence level. They cover a
broad range in [alpha/Fe] abundances from sub- to super-solar. The spectra of 3
UCDs show tentative evidence for intermediate age stellar populations. We
calculate the specific frequency (S_N) of UCDs for both groups, finding that
HCG 22 has about three times higher S_N than HCG 90. The ensemble properties of
the detected UCDs supports 2 co-existing formation channels: a star cluster
origin and an origin as tidally stripped dwarf nuclei. Our results imply that
the UCDs detected in both groups do not, in their majority, originate from
relatively recent galaxy interactions. Most of the detected UCDs have likely
been brought into the group with their host galaxies.[abridged]Comment: Accepted for publication at A&A, 17 pages, 9 figures + 2 additional
figure
Quantum Return Probability for Substitution Potentials
We propose an effective exponent ruling the algebraic decay of the average
quantum return probability for discrete Schrodinger operators. We compute it
for some non-periodic substitution potentials with different degrees of
randomness, and do not find a complete qualitative agreement with the spectral
type of the substitution sequences themselves, i.e., more random the sequence
smaller such exponent.Comment: Latex, 13 pages, 6 figures; to be published in Journal of Physics
Spinning dust emission: the effect of rotation around a non-principal axis
We investigate the rotational emission from dust grains that rotate around
non- principal axes. We argue that in many phases of the interstellar medium,
the smallest grains, which dominate spinning dust emission, are likely to have
their nutation state (orientation of principal axes relative to the angular
momentum vector) randomized during each thermal spike. We recompute the
excitation and damping rates associated with rotational emission from the grain
permanent dipole, grain-plasma interactions, infrared photon emission, and
collisions. The resulting spinning dust spectra gener- ally show a shift toward
higher emissivities and peak frequencies relative to previous calculations.Comment: Version accepted for publication in MNRAS. The derivation of the
emission spectrum was clarified. The companion code, SPDUST.2, can be
downloaded from http://www.tapir.caltech.edu/~yacine/spdust/spdust.htm
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