Dark matter from exact general relativistic thin disks in higher dimensions (Luc)

Abstract: The full three-year WMAP results (WMAP3) reinforce the absence of large-angle correlations at scales greater than 60 degrees. The Poincare dodecahedral space (PDS) model model, which may naturally explain such features, thus remains a plausible cosmological model, despite recent controversy about whether matched circle searches would or would not push the topology beyond the horizon. Here, we have used new eigenmode calculations of the dodecahedral space to predict the cosmic microwave background (CMB) temperature fluctuations in such models, with an improved angular resolution. We have simulated CMB maps and confirmed the expected presence of matching circles. For a set of plausible cosmological parameters, we have derived the angular power spectrum of the CMB up to large wavenumbers. Comparison with the WMAP3 observations confirms a remarkable fit with a PDS model, for a value $\Omega_0 = 1.018$ of the average total energy density.

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Abstract: The measurement of the scale of the baryon acoustic oscillations (BAO) in the galaxy power spectrum as a function of redshift is a promising method to constrain the equation-of-state parameter of the dark energy w. In order to measure precisely the scale of the BAO a huge volume has to be surveyed. We test whether light-cone effects become important and whether the scaling relations used to compensate for a wrong reference cosmology are accurate enough in this case. We compare two different fitting methods to extract the scale of the BAO. Further, we analyze the advantage of using the two-dimensional anisotropic power spectrum. Finally, we estimate the uncertainty with which an effectively constant w can be measured with proposed surveys around redshifts of z=3 and z=1, respectively. We find that light-cone effects for the simulated survey are negligible and that the simple scaling relations used to correct for the cosmological distortions work well even for such large survey volumes. The two different fitting approaches deliver consistent results and both should be considered further. The analysis of the two-dimensional anisotropic power spectra allows independent determination of the apparent scale of BAO perpendicular and parallel to the line of sight but it does not significantly lower the uncertainty of an effectively constant w. Nevertheless, for less constrained models of w independent measurements of the apparent scale of BAO perpendicular and parallel to the line of sight are essential. We estimate that with planned surveys around z=3 and z=1 one will be able to measure an effectively constant w with sigma_w ~ 4% in both cases.

Is Modified Gravity Required by Observations? An Empirical Consistency Test of Dark Energy Models (Alberto)

A Generic Test of Modified Gravity Models which Emulate Dark Matter

Abstract: We propose a generic test for models in which gravity is modified to do away with dark matter. These models tend to have gravitons couple to a different metric than ordinary matter. A strong test of such models comes from comparing the arrival time of the gravitational wave pulse from a cosmological event such as a supernova with the arrival times of the associated pulses of neutrinos and photons. For SN 1987a we show that the gravity wave would have arrived 5.3 days after the neutrino pulse.

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Cosmic rays from trans-relativistic supernovae

SUSY-GUTs, SUSY-Seesaw and the Neutralino Dark Matter

Abstract: We will consider a SUSY-SU(5) with one right-handed neutrino with a large top like Yukawa coupling. Assuming universal soft masses at high scale we compute the low-energy spectrum and subsequently the neutralino LSP relic density taking also into consideration SU(5) as well as the see-saw running effects above the gauge coupling unification scale. We found that there exists no viable region in parameter space for $\tan\beta~\ler 35$. The $\tilde{\tau}$ coannihilation process starts becoming efficient for $\tan\beta \ger 35-40$. However, unlike in mSUGRA, this process is significantly constrained by the limited range in which the stau is lighter than the neutralino. In fact, for a given $\tan\beta$ we find that there exists an upper bound on the lightest neutralino mass ($M_{\chi_1^0}$) in this region. The A-pole funnel region appears at very large $\tan\beta \sim 45-50$, while the focus-point region does not make an appearance till large ($m_0,M_{1/2})\sim$ a few TeV. Large $A_0$ terms at high scale can lead to extended regions consistent with WMAP constraints and remove the upper bounds in the stau coannihilation regions.

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Inflationary Perturbations: the Cosmological Schwinger Effect

Abstract: This pedagogical review aims at presenting the fundamental aspects of the theory of inflationary cosmological perturbations of quantum-mechanical origin. The analogy with the well-known Schwinger effect is discussed in detail and a systematic comparison of the two physical phenomena is carried out. In particular, it is demonstrated that the two underlying formalisms differ only up to an irrelevant canonical transformation. Hence, the basic physical mechanisms at play are similar in both cases and can be reduced to the quantization of a parametric oscillator leading to particle creation due to the interaction with a classical source: pair production in vacuum is therefore equivalent to the appearance of a growing mode for the cosmological fluctuations. The only difference lies in the nature of the source: an electric field in the case of the Schwinger effect and the gravitational field in the case of inflationary perturbations. Although, in the laboratory, it is notoriously difficult to produce an electric field such that pairs extracted from the vacuum can be detected, the gravitational field in the early universe can be strong enough to lead to observable effects that ultimately reveal themselves as temperature fluctuations in the Cosmic Microwave Background. Finally, the question of how quantum cosmological perturbations can be considered as classical is discussed at the end of the article.

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PArthENoPE: Public Algorithm Evaluating the Nucleosynthesis of Primordial Elements