3,951 research outputs found
Stationary Black Holes in a Generalized Three-Dimensional Theory of Gravity
We consider a generalized three-dimensional theory of gravity which is
specified by two fields, the graviton and the dilaton, and one parameter. This
theory contains, as particular cases, three-dimensional General Relativity and
three-dimensional String Theory. Stationary black hole solutions are generated
from the static ones using a simple coordinate transformation. The stationary
black holes solutions thus obtained are locally equivalent to the corresponding
static ones, but globally distinct. The mass and angular momentum of the
stationary black hole solutions are computed using an extension of the Regge
and Teitelboim formalism. The causal structure of the black holes is described.Comment: 12 pages, Late
Generation of Superposition States and Charge-Qubit Relaxation Probing in a Circuit
We demonstrate how a superposition of coherent states can be generated for a
microwave field inside a coplanar transmission line coupled to a single
superconducting charge qubit, with the addition of a single classical magnetic
pulse for chirping of the qubit transition frequency. We show how the qubit
dephasing induces decoherence on the field superposition state, and how it can
be probed by the qubit charge detection. The character of the charge qubit
relaxation process itself is imprinted in the field state decoherence profile.Comment: 6 pages, 4 figure
Pion-Pion Phase-Shifts and the Value of Quark-Antiquark Condensate in the Chiral Limit
We use low energy pion-pion phase-shifts in order to make distinction between
the alternatives for the value of the quark-antiquark condensate in the
chiral limit. We will consider the amplitude up to and including contributions within the Standard and Generalized Chiral Perturbation
Theory frameworks. They are unitarized by means of Pad\'e approximants in order
to fit experimental phase-shifts in the resonance region. As the best fits
correspond to , we conclude that pion-pion phase-shift
analysis favors the standard ChPT scenario, which assumes just one, large
leading order parameter .Comment: 5 pages, 3 figures and 1 tabl
Temperature Measurement and Phonon Number Statistics of a Nanoelectromechanical Resonator
Measuring thermodynamic quantities can be easy or not, depending on the
system that is being studied. For a macroscopic object, measuring temperatures
can be as simple as measuring how much a column of mercury rises when in
contact with the object. At the small scale of quantum electromechanical
systems, such simple methods are not available and invariably detection
processes disturb the system state. Here we propose a method for measuring the
temperature on a suspended semiconductor membrane clamped at both ends. In this
method, the membrane is mediating a capacitive coupling between two
transmission line resonators (TLR). The first TLR has a strong dispersion, that
is, its decaying rate is larger than its drive, and its role is to pump in a
pulsed way the interaction between the membrane and the second TLR. By
averaging the pulsed measurements of the quadrature of the second TLR we show
how the temperature of the membrane can be determined. Moreover the statistical
description of the state of the membrane, which is directly accessed in this
approach is significantly improved by the addition of a Josephson Junction
coupled to the second TLR.Comment: 9 pages, 5 figures. To appear in New Journal of Physic
Gravitational wave generation in hybrid quintessential inflationary models
We investigate the generation of gravitational waves in the hybrid
quintessential inflationary model. The full gravitational-wave energy spectrum
is calculated using the method of continuous Bogoliubov coefficients. The
post-inflationary kination period, characteristic of quintessential
inflationary models, leaves a clear signature on the spectrum, namely, a peak
at high frequencies. The maximum of the peak is firmly located at the MHz-GHz
region of the spectrum and corresponds to . This
peak is substantially smaller than the one appearing in the gravitational-wave
energy spectrum of the original quintessential inflationary model, therefore
avoiding any conflict with the nucleosynthesis constraint on
\Omega_\Omega_{GW}.Comment: 10 pages, 11 figures, one reference adde
Capacitive Coupling of Two Transmission Line Resonators Mediated by the Phonon Number of a Nanoelectromechanical Oscillator
Detection of quantum features in mechanical systems at the nanoscale
constitutes a challenging task, given the weak interaction with other elements
and the available technics. Here we describe how the interaction between two
monomodal transmission-line resonators (TLRs) mediated by vibrations of a
nano-electromechanical oscillator can be described. This scheme is then
employed for quantum non-demolition detection of the number of phonons in the
nano-electromechanical oscillator through a direct current measurement in the
output of one of the TLRs. For that to be possible an undepleted field inside
one of the TLR works as a amplifier for the interaction between the mechanical
resonator and the remaining TLR. We also show how how the non-classical nature
of this system can be used for generation of tripartite entanglement and
conditioned mechanical coherent superposition states, which may be further
explored for detection processes.Comment: 6 pages, 5 figure
Adaptation to β-myrcene catabolism in Pseudomonas sp. M1: An expression proteomics analysis
β-Myrcene, a monoterpene widely used as a fragrance and flavoring additive, also possesses analgesic, anti-mutagenic, and tyrosinase inhibitory properties. In order to get insights into the molecular mechanisms underlying the ability of Pseudomonas sp. M1 to catabolize β-myrcene, an expression proteomics approach was used in this study. Results indicate that the catabolic enzyme machinery for β-myrcene utilization (MyrB, MyrC, and MyrD and other uncharacterized proteins) is strongly induced when β-myrcene is present in the growth medium. Since an M1 mutant, lacking a functional 2-methylisocitrate dehydratase, is not able to grow in mineral medium with β-myrcene or propionic acid as the sole C-source, and also based on the expression proteomic analysis carried out in this study, it is suggested that the β-myrcene catabolic intermediate propionyl-CoA is channeled into the central metabolism via the 2-methylcitrate cycle. Results also suggest that the major alteration occurring in the central carbon metabolism of cells growing in β-myrcene-containing media is related with the redistribution of the metabolic fluxes leading to increased oxaloacetate production. Other upregulated proteins are believed to prevent protein misfolding and aggregation or to play important structural roles, contributing to the adaptive alteration of cell wall and membrane organization and integrity, which are essential features to allow the bacterium to cope with the highly lipophilic β-myrcene as C-source.- (undefined
Gravitational wave generation in loop quantum cosmology
We calculate the full spectrum, as observed today, of the cosmological
gravitational waves generated within a model based on loop quantum cosmology.
It is assumed that the universe, after the transition to the classical regime,
undergoes a period of inflation driven by a scalar field with a chaotic-type
potential. Our analysis shows that, for certain conditions, loop quantum
effects leave a clear signature on the spectrum, namely, an over-production of
low-frequency gravitational waves. One of the aims of our work is to show that
loop quantum cosmology models can be tested and that, more generally,
pre-inflationary physical processes, contrary to what is usually assumed, leave
their imprint in those spectra and can also be tested.Comment: 7 pages, 8 figures, revtex
Arquiteturas funerárias, materiais de construção e interação com o espaço na Idade do Bronze da Serra da Freita (Centro-Norte de Portugal). O caso do tumulus de Laceiras do Côvo 3, Vale de Cambra
Pretende-se com este artigo dar a conhecer os resultados dos trabalhos arqueológicos levados a cabo no monu-mento funerário de Laceiras do Côvo 3, estrutura tumular enquadrável, provavelmente, na Idade do Bronze, localizada na freguesia de Arões, concelho de Vale de Cambra. Este monumento revela-se de particular inte-resse pela policromia intencional na matéria usada na sua construção e pela disposição cuidada dos elementos litológicos do tumulus, em que nada parece estar ao acaso. Tais caracterÃsticas sugerem a intenção de manter o espaço dos mortos visÃvel, assim como uma interligação simbólica entre rochas e minerais e as práticas relacio-nadas com a morte. Na linha de Tim Ingold (2000) consideramos, ainda, que a matéria do monumento seria portadora de determinadas propriedades, revelando-se como entidade viva e atuante na construção de sentidos e memórias associadas ao mundo dos mortos.Fundação para a Ciência e a Tecnologia (FCT
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