20,373 research outputs found
Stabilizing Entangled States with Quasi-Local Quantum Dynamical Semigroups
We provide a solution to the problem of determining whether a target pure
state can be asymptotically prepared using dissipative Markovian dynamics under
fixed locality constraints. Beside recovering existing results for a large
class of physically relevant entangled states, our approach has the advantage
of providing an explicit stabilization test solely based on the input state and
constraints of the problem. Connections with the formalism of frustration-free
parent Hamiltonians are discussed, as well as control implementations in terms
of a switching output-feedback law.Comment: 11 pages, no figure
Dark Matter Seeding in Neutron Stars
We present a mechanism that may seed compact stellar objects with stable
lumps of quark matter, or {\it strangelets}, through the self-annihilation of
gravitationally accreted WIMPs. We show that dark matter particles with masses
above a few GeV may provide enough energy in the nuclear medium for quark
deconfinement and subsequent strangelet formation. If this happens this effect
may then trigger a partial or full conversion of the star into a strange star.
We set a new limit on the WIMP mass in the few-GeV range that seems to be
consistent with recent indications in dark matter direct detection experiments.Comment: 3 pages, 1 figure. Prepared for 19th Particles and Nuclei
International Conference (PANIC 2011), Boston, USA 25-29 Jul 201
Analysis of the acoustic cut-off frequency and HIPs in six Kepler stars with stochastically excited pulsations
Gravito-acoustic modes in the Sun and other stars propagate in resonant
cavities with a frequency below a given limit known as the cut-off frequency.
At higher frequencies, waves are no longer trapped in the stellar interior and
become traveller waves. In this article we study six pulsating solar-like stars
at different evolutionary stages observed by the NASA Kepler mission. These
high signal-to-noise targets show a peak structure that extends at very high
frequencies and are good candidates for studying the transition region between
the modes and the interference peaks or pseudo-modes. Following the same
methodology successfully applied on Sun-as-a-star measurements, we uncover the
existence of pseudo-modes in these stars with one or two dominant interference
patterns depending on the evolutionary stage of the star. We also infer their
cut-off frequency as the midpoint between the last eigenmode and the first peak
of the interference patterns. By using ray theory we show that, while the
period of one of the interference pattern is very close to half the large
separation the other, one depends on the time phase of mixed waves, thus
carrying additional information on the stellar structure and evolution.Comment: Accepted for publication in A&A. 14 pages, 28 figure
Personal relatedness and attachment in infants of mothers with borderline personality disorder
The principal aim of this study was to assess personal relatedness and attachment patterns in 12-month-old infants of mothers with borderline personality disorder (BPD). We also evaluated maternal intrusive insensitivity toward the infants in semistructured play. We videotaped 10 mother-infant dyads with borderline mothers and 22 dyads where the mothers were free from psychopathology, in three different settings: a modification of Winnicott's Set Situation in which infants faced an initially unresponsive ("still-face") stranger, who subsequently tried to engage the infant in a game of give and take; the Strange Situation of Ainsworth and Wittig; and a situation in which mothers were requested to teach their infants to play with miniature figures and a toy train. In relation to a set of a priori predictions, the results revealed significant group differences as follows: (a) compared with control infants, toward the stranger the infants of mothers with BPD showed lower levels of "availability for positive engagement," lower ratings of "behavior organization and mood state," and a lower proportion of interpersonally directed looks that were positive; (b) in the Strange Situation, a higher proportion (8 out of 10) of infants of borderline mothers were categorized as Disorganized; and (c) in play, mothers with BPD were rated as more "intrusively insensitive" toward their infants. The results are discussed in relation to hypotheses concerning the interpersonal relations of women with BPD, and possible implications for their infants' development
Dark matter, neutron stars and strange quark matter
We show that self-annihilating neutralino WIMP dark matter accreted onto
neutron stars may provide a mechanism to seed compact objects with long-lived
lumps of strange quark matter, or strangelets, for WIMP masses above a few GeV.
This effect may trigger a conversion of most of the star into a strange star.
We use an energy estimate for the long-lived strangelet based on the Fermi gas
model combined with the MIT bag model to set a new limit on the possible values
of the WIMP mass that can be especially relevant for subdominant species of
massive neutralinos.Comment: 5 pages, 2 figures, accepted for publication in Phys. Rev. Let
Efficient measurement-based quantum computing with continuous-variable systems
We present strictly efficient schemes for scalable measurement-based quantum
computing using continuous-variable systems: These schemes are based on
suitable non-Gaussian resource states, ones that can be prepared using
interactions of light with matter systems or even purely optically. Merely
Gaussian measurements such as optical homodyning as well as photon counting
measurements are required, on individual sites. These schemes overcome
limitations posed by Gaussian cluster states, which are known not to be
universal for quantum computations of unbounded length, unless one is willing
to scale the degree of squeezing with the total system size. We establish a
framework derived from tensor networks and matrix product states with infinite
physical dimension and finite auxiliary dimension general enough to provide a
framework for such schemes. Since in the discussed schemes the logical encoding
is finite-dimensional, tools of error correction are applicable. We also
identify some further limitations for any continuous-variable computing scheme
from which one can argue that no substantially easier ways of
continuous-variable measurement-based computing than the presented one can
exist.Comment: 13 pages, 3 figures, published versio
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