1,174 research outputs found
Testing Primordial Black Holes as Dark Matter through LISA
The idea that primordial black holes (PBHs) can comprise most of the dark
matter of the universe has recently reacquired a lot of momentum. Observational
constraints, however, rule out this possibility for most of the PBH masses,
with a notable exception around . These light PBHs may be
originated when a sizeable comoving curvature perturbation generated during
inflation re-enters the horizon during the radiation phase. During such a
stage, it is unavoidable that gravitational waves (GWs) are generated. Since
their source is quadratic in the curvature perturbations, these GWs are
generated fully non-Gaussian. Their frequency today is about the mHz, which is
exactly the range where the LISA mission has the maximum of its sensitivity.
This is certainly an impressive coincidence. We show that this scenario of PBHs
as dark matter can be tested by LISA by measuring the GW two-point correlator.
On the other hand, we show that the short observation time (as compared to the
age of the universe) and propagation effects of the GWs across the perturbed
universe from the production point to the LISA detector suppress the bispectrum
to an unobservable level. This suppression is completely general and not
specific to our model.Comment: 22 pages, 12 figures. v3: matching published versio
Can unstable relics save pure Cold Dark Matter?
The standard CDM model fails to describe the power spectrum of fluctuations since it gives too much power at small scales. Among other possible improvements, it has been suggested that an agreement with observations can be achieved with the addition of a late decaying particle, through the injection of non-thermal radiation and the consequent increase of the horizon length at the equivalence time. We analyze the possibility of implementing this idea in extensions of the electroweak standard model, with particular attention to supersymmetry with and without R-parity. After considering cosmological and astrophysical bounds, only few candidate models survive as viable solutions
Persistent Challenges of Quantum Chromodynamics
Unlike some models whose relevance to Nature is still a big question mark,
Quantum Chromodynamics will stay with us forever. Quantum Chromodynamics (QCD),
born in 1973, is a very rich theory supposed to describe the widest range of
strong interaction phenomena: from nuclear physics to Regge behavior at large
E, from color confinement to quark-gluon matter at high densities/temperatures
(neutron stars); the vast horizons of the hadronic world: chiral dynamics,
glueballs, exotics, light and heavy quarkonia and mixtures thereof, exclusive
and inclusive phenomena, interplay between strong forces and weak interactions,
etc. Efforts aimed at solving the underlying theory, QCD, continue. In a
remarkable entanglement, theoretical constructions of the 1970s and 1990s
combine with today's ideas based on holographic description and strong-weak
coupling duality, to provide new insights and a deeper understanding.Comment: Julius Edgar Lilienfeld Prize Lecture at the April Meeting of APS,
Dallas, TX, April 22-25, 2006; v.2: reference added; v.3: reference adde
Preheating with Trilinear Interactions: Tachyonic Resonance
We investigate the effects of bosonic trilinear interactions in preheating
after chaotic inflation. A trilinear interaction term allows for the complete
decay of the massive inflaton particles, which is necessary for the transition
to radiation domination. We found that typically the trilinear term is
subdominant during early stages of preheating, but it actually amplifies
parametric resonance driven by the four-legs interaction. In cases where the
trilinear term does dominate during preheating, the process occurs through
periodic tachyonic amplifications with resonance effects, which is so effective
that preheating completes within a few inflaton oscillations. We develop an
analytic theory of this process, which we call tachyonic resonance. We also
study numerically the influence of trilinear interactions on the dynamics after
preheating. The trilinear term eventually comes to dominate after preheating,
leading to faster rescattering and thermalization than could occur without it.
Finally, we investigate the role of non-renormalizable interaction terms during
preheating. We find that if they are present they generally dominate (while
still in a controllable regime) in chaotic inflation models. Preheating due to
these terms proceeds through a modified form of tachyonic resonance.Comment: 19 pages, 10 figures, refs added, published versio
Avaliação de linhagens de feijão do grupo comercial carioca no Estado de Sergipe no ano agrícola 2001.
Objetivando selecionar genótipos de feijão do grupo carioca mais produtivos e melhor adaptados às condições edafoclimáticas do Estado, foram estabelecidos três experimentos em 2001, sendo 2 ensaios realizados no Município de Simão Dias (Ensaios Nacionais de Feijão dos Grupos Comerciais Carioca A e B) e um outro ensaio instalado no Município de Umbaúba (Ensaio Nacional de Feijão do Grupo Comercial C)
Avaliação de linhagens de feijão do grupo mulatinho do Estado de Sergipe.
Desenvolveu-se este trabalho visando à seleção de linhagens superiores de feijão do grupo mulatinho para fins de exploração na região. Este tipo de feijão de grãos mais pequenos, segundo Voysest, 1983, é originário da América Central, sendo um dos tipos preferidos dos brasileiros
Low-scale inflation in a model of dark energy and dark matter
We present a complete particle physics model that explains three major
problems of modern cosmology: inflation, dark matter and dark energy, and also
gives a mechanism for leptogenesis. The model has a new gauge group
that grows strong at a scale eV. We focus on the
inflationary aspects of the model. Inflation occurs with a Coleman-Weinberg
potential at a low scale, down to \sim 6\times 10^5\gev, being compatible
with observational data.Comment: 5 two-column pages, RevTex4; two reference added and minor changes
made in the text; published in JCA
Definition of Nonresponse to Analgesic Treatment of Arthritic Pain: An Analytical Literature Review of the Smallest Detectable Difference, the Minimal Detectable Change, and the Minimal Clinically Important Difference on the Pain Visual Analog Scale
Our objective was to develop a working definition of nonresponse to analgesic treatment of arthritis, focusing on the measurement of pain on the 0–100 mm pain visual analog scale (VAS). We reviewed the literature to assess the smallest detectable difference (SDD), the minimal detectable change (MDC), and the minimal clinically important difference (MCID). The SDD for improvement reported in three studies of rheumatoid arthritis was 18.6, 19.0, and 20.0. The median MDC was 25.4 for 7 studies of osteoarthritis and 5 studies of rheumatoid arthritis (calculated for a reliability coefficient of 0.85). The MCID increased with increasing baseline pain score. For baseline VAS tertiles defined by scores of 30–49, 50–65, and >65, the MCID for improvement was, respectively, 7–11 units, 19–27 units, and 29–37 units. Nonresponse can thus be defined in terms of the MDC for low baseline pain scores and in terms of the MCID for high baseline scores
Characterizing the cosmological gravitational wave background: Anisotropies and non-Gaussianity
A future detection of the stochastic gravitational wave background (SGWB) with gravitational wave (GW) experiments is expected to open a new window on early universe cosmology and on the astrophysics of compact objects. In this paper we study SGWB anisotropies, that can offer new tools to discriminate between different sources of GWs. In particular, the cosmological SGWB inherits its anisotropies both (i) at its production and (ii) during its propagation through our perturbed universe. Concerning (i), we show that it typically leads to anisotropies with order one dependence on frequency. We then compute the effect of (ii) through a Boltzmann approach, including contributions of both large-scale scalar and tensor linearized perturbations. We also compute for the first time the three-point function of the SGWB energy density, which can allow one to extract information on GW non-Gaussianity with interferometers. Finally, we include nonlinear effects associated with long wavelength scalar fluctuations, and compute the squeezed limit of the 3-point function for the SGWB density contrast. Such limit satisfies a consistency relation, conceptually similar to that found in the literature for the case of cosmic microwave background perturbations
Damage of cowpea mild mottle virus and incidence of Bemisia tabaci biotype B in transgenic common bean lines resistant to bean golden mosaic virus.
The development of Embrapa 5.1 event of genetically modified (GM) common bean resistant to BGMV, and near isogenic lines of two commercial cultivars (Pérola and BRS Pontal) allows the evaluation of the damage caused only by CpMMV.This is because these transgenic isolines do not get infected by BGMV
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