19,201 research outputs found
Dynamically localized systems: entanglement exponential sensitivity and efficient quantum simulations
We study the pairwise entanglement present in a quantum computer that
simulates a dynamically localized system. We show that the concurrence is
exponentially sensitive to changes in the Hamiltonian of the simulated system.
Moreover, concurrence is exponentially sensitive to the ``logic'' position of
the qubits chosen. These sensitivities could be experimentally checked
efficiently by means of quantum simulations with less than ten qubits. We also
show that the feasibility of efficient quantum simulations is deeply connected
to the dynamical regime of the simulated system.Comment: 5 pages, 6 figure
Massive young clusters in the disc of M31
We have studied the properties of a sample of 67 very blue and likely young
massive clusters in M31 extracted from the Bologna Revised Catalog of globular
clusters, selected according to their color [(B-V) < 0.45] and/or to the
strength of their Hbeta spectral index (Hbeta > 3.5 A). Their existence in M31
has been noted by several authors in the past; we show here that these Blue
Luminous Compact Clusters (BLCCs) are a significant fraction (>~ 15%) of the
whole globular cluster system of M31. Compared to the global properties of the
M31 globular cluster system, they appear to be intrinsically fainter,
morphologically less concentrated, and with a shallower Balmer jump and
enhanced absorption in their spectra.
Empirical comparison with integrated properties of clusters with known age as
well as with theoretical SSP models consistently indicate that their typical
age is less than ~2 Gyr, while they probably are not so metal-poor as deduced
if considered to be old. Either selecting BLCCs by their (B-V) colors or by the
strength of their Hbeta index the cluster sample turns out to be distributed
onto the outskirts of M31 disc, sharing the kinematical properties of the thin,
rapidly rotating disc component.
If confirmed to be young and not metal-poor, these clusters indicate the
occurrence of a significant recent star formation in the thin disc of M31,
although they do not set constraints on the epoch of its early formation.Comment: Submitted for publication in the Astronomical Journal. Aastex Latex
file of 22 pages, 12 figures and 3 table
Infinite index extensions of local nets and defects
Subfactor theory provides a tool to analyze and construct extensions of
Quantum Field Theories, once the latter are formulated as local nets of von
Neumann algebras. We generalize some of the results of [LR95] to the case of
extensions with infinite Jones index. This case naturally arises in physics,
the canonical examples are given by global gauge theories with respect to a
compact (non-finite) group of internal symmetries. Building on the works of
Izumi, Longo, Popa [ILP98] and Fidaleo, Isola [FI99], we consider generalized
Q-systems (of intertwiners) for a semidiscrete inclusion of properly infinite
von Neumann algebras, which generalize ordinary Q-systems introduced by Longo
[Lon94] to the infinite index case. We characterize inclusions which admit
generalized Q-systems of intertwiners and define a braided product among the
latter, hence we construct examples of QFTs with defects (phase boundaries) of
infinite index, extending the family of boundaries in the grasp of [BKLR16].Comment: 50 page
Hamiltonian analysis of subcritical stochastic epidemic dynamics
We extend a technique of approximation of the long-term behavior of a
supercritical stochastic epidemic model, using the WKB approximation and a
Hamiltonian phase space, to the subcritical case. The limiting behavior of the
model and approximation are qualitatively different in the subcritical case,
requiring a novel analysis of the limiting behavior of the Hamiltonian system
away from its deterministic subsystem. This yields a novel, general technique
of approximation of the quasistationary distribution of stochastic epidemic and
birth-death models, and may lead to techniques for analysis of these models
beyond the quasistationary distribution. For a classic SIS model, the
approximation found for the quasistationary distribution is very similar to
published approximations but not identical. For a birth-death process without
depletion of susceptibles, the approximation is exact. Dynamics on the phase
plane similar to those predicted by the Hamiltonian analysis are demonstrated
in cross-sectional data from trachoma treatment trials in Ethiopia, in which
declining prevalences are consistent with subcritical epidemic dynamics
Problematizações das práticas psi : articulações com o pensamento foucaultiano
A problematização das práticas de intervenção na área psi tem sido orientada, muitas vezes, por alguns conceitos foucaultianos como poder, saber e regimes de verdade e tem introduzido questões diferenciadas em relação àquelas que tradicionalmente tem-se caracterizado como uma compreensão do que são as práticas psicológicas. Se por um lado essas reflexões passam por uma desacomodação produzidas pelo olhar foucaultiano, por outro lado, esse incômodo é suscitado pelas práticas psicológicas tradicionais que desfrutam de um estatuto de legitimidade. Esses questionamentos instigam o pensar sobre deslocamentos nas formas de intervenção e compreensão das práticas psi.The problematization of the practices of intervention in Psychology has been helped by foucauldian concepts such as power, knowledge, and truth regimes. These concepts have altered the questions which have traditionally characterized views of psychological practices. However, such analysis has been accused of focusing only on the condition of visibility of power relations and modes of production of truth regimes, instead of instituting new forms of action or intervention. In this article we aim to produce a space for new links between foucauldian thought and current ways of conceiving the interventions in the psychology field
Fractal Fidelity as a signature of Quantum Chaos
We analyze the fidelity of a quantum simulation and we show that it displays
fractal fluctuations iff the simulated dynamics is chaotic. This analysis
allows us to investigate a given simulated dynamics without any prior
knowledge. In the case of integrable dynamics, the appearance of fidelity
fractal fluctuations is a signal of a highly corrupted simulation. We
conjecture that fidelity fractal fluctuations are a signature of the appearance
of quantum chaos. Our analysis can be realized already by a few qubit quantum
processor.Comment: 5 pages, 5 figure
Leptogenesis in models with keV sterile neutrino dark matter
We analyze leptogenesis in gauge extensions of the Standard Model with keV
sterile neutrino dark matter. We find that both the observed dark matter
abundance and the correct baryon asymmetry of the Universe can simultaneously
emerge in these models. Both the dark matter abundance and the leptogenesis are
controlled by the out of equilibrium decays of the same heavy right handed
neutrino.Comment: 6 pages, 1 figur
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