2,221 research outputs found
Tachyonic Quintessential Inflation
We study the possibility to construct an observationally viable scenario
where both early Inflation and the recently detected accelerated expansion of
the universe can be explained by using a single scalar field associated with
the Tachyon. The Reheating phase becomes crucial to enable us to have a
consistent cosmology and also to get a second accelerated expansion period. A
discussion using an exponential potential is presented.Comment: 5 pages, Revtex4. Added some references. To be published in Physical
Review
Dark energy and Dark matter interaction in light of the second law of thermodynamics
In the context of thermodynamics we discuss the way inevitable emerge an
interaction between dark components, and in this way, provide a mechanism to
understand the limits of the LCDM model and the class of interaction models
between dark components. Using observational data we have tested two models of
explicit interaction between dark components and reconstructed the evolution of
temperatures for both components. We found that observations suggest the
interaction exist with energy flowing from dark energy to dark matter. The best
fit also suggest a phantom equation of state parameter for dark energy. We
discuss the results having in mind the constraints imposed by thermodynamics.Comment: 18 pages, 4 figure
COOPERATION IN LARGE NETWORKS: AN EXPERIMENTAL
We present a new design of a simple public goods experiment with a large number of players, where up to 80 people in a computer lab have the possibility to connect with others in the room to induce more cooperators to contribute to the public good and overcome the social dilemma. This experimental design explores the possibility of social networks to be used and institutional devices to create the same behavioral responses we observe with small groups (e.g. commitments, social norms, reciprocity, trust, shame, guilt) that seem to induce cooperativebehavior in the private provision of public goods. The results of our experiment suggest that the structure of the network affects not only the players´ ability to communicate, but their willingness to do so as well. Finally, we find that the local connectivity structure of the network has an important role as determinant of the willingness of the players to engage in a more costly type of collective action, namely the endogenous creation of new links to individuals previously out of reach.Social capital, social networks, collective action, cooperation, VCM,experiments, public goods provision
The Higgs decay rate to two photons in a model with two fermiophobic-Higgs doublets
We consider a three Higgs doublet model with an symmetry in which
beside the SM-like doublet there are two fermiophobic doublets. Due to the new
charged scalars there is an enhancement in the two-photon decay while the other
channels have the same decay widths that the SM neutral Higgs. The fermiophobic
scalars are mass degenerated unless soft terms breaking the symmetry are
added.Comment: typos were corrected, the figures have been modified and the
conclusions were increased. Still contains 15 pages, 2 figure
Degree of Quantumness in Quantum Synchronization
We introduce the concept of degree of quantumness in quantum synchronization,
a measure of the quantum nature of synchronization in quantum systems.
Following techniques from quantum information, we propose the number of
non-commuting observables that synchronize as a measure of quantumness. This
figure of merit is compatible with already existing synchronization
measurements, and it captures different physical properties. We illustrate it
in a quantum system consisting of two weakly interacting cavity-qubit systems,
which are coupled via the exchange of bosonic excitations between the cavities.
Moreover, we study the synchronization of the expectation values of the Pauli
operators and we propose a feasible superconducting circuit setup. Finally, we
discuss the degree of quantumness in the synchronization between two quantum
van der Pol oscillators
R^2-corrections to Chaotic Inflation
Scalar density cosmological perturbations, spectral indices and reheating in
a chaotic inflationary universe model, in which a higher derivative term is
added, are investigated. This term is supposed to play an important role in the
early evolution of the Universe, specifically at times closer to the Planck
era.Comment: 14 pages, accepted for publication in MPL
A fractal LTB model cannot explain Dark Energy
We revisited the problem of describing, on average, a fractal distribution of
matter using a Lemaitre-Tolman-Bondi (LTB) solution. Here we study the fractal
structure of our local universe having a fractal dimension and a scale
transition. We test our model with the latest type Ia supernova data, the
Pantheon compilation, and discuss problems and possible improvements for it,
concluding that a fractal transition in LTB cosmology cannot be used to explain
the effects of dark energy but it can be useful to study structures at low
scales
On the Orbital Period of the Intermediate Polar 1WGA J1958.2+3232
Recently, Norton et al. 2002, on the basis of multiwavelength photometry of
1WGA J1958.2+3232, argued that the -1 day alias of the strongest peak in the
power spectrum is the true orbital period of the system, casting doubts on the
period estimated by Zharikov et al. 2001. We re-analyzed this system using our
photometric and spectroscopic data along with the data kindly provided by Andy
Norton and confirm our previous finding. After refining our analysis we find
that the true orbital period of this binary system is 4.35h.Comment: 4 pages, 5 figures, Accepted for publication in A&A Letter
Resonance enhancement of particle production during reheating
We found a consistent equation of reheating after inflation, which shows that
for small quantum fluctuations the frequencies of resonance are slighted
different from the standard ones. Quantum interference is taken into account
and we found that at large fluctuations the process mimics very well the usual
parametric resonance but proceed in a different dynamical way. The analysis is
made in a toy quantum mechanical model and we discuss further its extension to
quantum field theory.Comment: 4 pages, 4 figures(eps), using RevTe
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