COSMOLOGY AND GRAVITATION: XIth Brazilian School of Cosmology and Gravitation
782(2005); http://dx.doi.org/10.1063/1.2032727View Description Hide Description
These are extended notes of a series of lectures given at the XIth Brazilian School of Cosmology and Gravitation. They provide a selection of topics at the intersection of particle and astrophysics. The first part gives a short introduction to the theory of electroweak interactions, with specific emphasize on neutrinos. In the second part we apply this framework to selected topics in astrophysics and cosmology, namely neutrino oscillations, neutrino hot dark dark matter, and big bang nucleosynthesis. The last part is devoted to ultra high energy cosmic rays and neutrinos where again particle physics aspects are emphasized. The often complementary role of laboratory experiments is also discussed in several examples.
The Blackholic energy: long and short Gamma‐Ray Bursts (New perspectives in physics and astrophysics from the theoretical understanding of Gamma‐Ray Bursts, II)782(2005); http://dx.doi.org/10.1063/1.2032728View Description Hide Description
We outline the confluence of three novel theoretical fields in our modeling of Gamma‐Ray Bursts (GRBs): 1) the ultrarelativistic regime of a shock front expanding with a Lorentz gamma factor ∼ 300; 2) the quantum vacuum polarization process leading to an electron‐positron plasma originating the shock front; and 3) the general relativistic process of energy extraction from a black hole originating the vacuum polarization process. There are two different classes of GRBs: the long GRBs and the short GRBs. We here address the issue of the long GRBs. The theoretical understanding of the long GRBs has led to the detailed description of their luminosities in fixed energy bands, of their spectral features and made also possible to probe the astrophysical scenario in which they originate. We are specially interested, in this report, to a subclass of long GRBs which appear to be accompanied by a supernova explosion. We are considering two specific examples: GRB980425/SN1998bw and GRB030329/SN2003dh. While these supernovae appear to have a standard energetics of 1049 ergs, the GRBs are highly variable and can have energetics 104 – 105 times larger than the ones of the supernovae. Moreover, many long GRBs occurs without the presence of a supernova. It is concluded that in no way a GRB can originate from a supernova. The precise theoretical understanding of the GRB luminosity we present evidence, in both these systems, the existence of an independent component in the X‐ray emission, usually interpreted in the current literature as part of the GRB afterglow. This component has been observed by Chandra and XMM to have a strong decay on scale of months. We have named here these two sources respectively URCA‐1 and URCA‐2, in honor of the work that George Gamow and Mario Shoenberg did in 1939 in this town of Urca identifying the basic mechanism, the Urca processes, leading to the process of gravitational collapse and the formation of a neutron star and a supernova. The further hypothesis is considered to relate this X‐ray source to a neutron star, newly born in the Supernova. This hypothesis should be submitted to further theoretical and observational investigation. Some theoretical developments to clarify the astrophysical origin of this new scenario are outlined. We turn then to the theoretical developments in the short GRBs: we first report some progress in the understanding the dynamical phase of collapse, the mass‐energy formula and the extraction of blackholic energy which have been motivated by the analysis of the short GRBs. In this context progress has also been accomplished on establishing an absolute lower limit to the irreducible mass of the black hole as well as on some critical considerations about the relations of general relativity and the second law of thermodynamics. We recall how this last issue has been one of the most debated in theoretical physics in the past thirty years due to the work of Bekenstein and Hawking. Following these conceptual progresses we analyze the vacuum polarization process around an overcritical collapsing shell. We evidence the existence of a separatrix and a dyadosphere trapping surface in the dynamics of the electron‐positron plasma generated during the process of gravitational collapse. We then analyze, using recent progress in the solution of the Vlasov‐Boltzmann‐Maxwell system, the oscillation regime in the created electron‐positron plasma and their rapid convergence to a thermalized spectrum. We conclude by making precise predictions for the spectra, the energy fluxes and characteristic time‐scales of the radiation for short‐bursts. If the precise luminosity variation and spectral hardening of the radiation we have predicted will be confirmed by observations of short‐bursts, these systems will play a major role as standard candles in cosmology. These considerations will also be relevant for the analysis of the long‐bursts when the baryonic matter contribution will be taken into account.
782(2005); http://dx.doi.org/10.1063/1.2032729View Description Hide Description
This review provides an outline of both the astrophysical and experimental aspects of gravitational wave physics. Divided into five parts, the first section gives an introduction to the field, briefly discussing significance and methods used for detection. Section 2 focusses on the different sources of gravitational waves and their expected signal strengths. We also discuss the significance of the new binary system PSR J0737‐3039 to gravitational wave physics. In section 3, the methods and assumptions used to model the temporal evolution of a stochastic gravitational wave background are presented. Resonant mass detectors are the subject of section 4, in which relevant concepts and issues are discussed in more detail. This section includes the fundamental noise sources and methods of improving on current designs. The final section, focuses on interferometric gravitational wave detection. Optical layout, vibration isolation and thermal noise are discussed in regards to maximizing detector sensitivity.
782(2005); http://dx.doi.org/10.1063/1.2032730View Description Hide Description
The cosmological constant problem as well as the case for dark energy are briefly reviewed and some theoretical models of dark energy are discussed in detail. These include: the cosmological constant, quintessence, the Chaplygin gas and Braneworld models. I also discuss model independent measures of dark energy and conclude by mentioning some properties of the Statefinder diagnostic which can successfully differentiate between different families of dark energy models.
782(2005); http://dx.doi.org/10.1063/1.2032731View Description Hide Description
Whether we live in a spatially finite universe, and what its shape and size may be, are among the fundamental longstanding questions in cosmology. These questions of topological nature have become particularly topical, given the wealth of increasingly accurate astro‐cosmological observations, especially the recent observations of the cosmic microwave background radiation. An overview of the basic context of cosmic topology, the detectability constraints from recent observations, as well as the main methods for its detection and some recent results are presented.
782(2005); http://dx.doi.org/10.1063/1.2032732View Description Hide Description
This course is an introduction to the physics of braneworlds. We concentrate on braneworlds with only one extra‐dimension and discuss their gravity. We derive the gravitational equations on the brane from the bulk Einstein equation and explore some limits in which they reduce to 4‐dimensional Einstein gravity. We indicate how cosmological perturbations from braneworlds are probably very different from usual cosmological perturbations and give some examples of the preliminary results in this active field of research.
For completeness, we also present an introduction to 4‐dimensional cosmological perturbation theory and, especially its application to the anisotropies of the cosmic microwave background.
782(2005); http://dx.doi.org/10.1063/1.2032733View Description Hide Description
These notes summarize a set of lectures on phenomenological quantum gravity which one of us delivered and the other attended with great diligence. They cover an assortment of topics on the border between theoretical quantum gravity and observational anomalies. Specifically, we review non‐linear relativity in its relation to loop quantum gravity and high energy cosmic rays. Although we follow a pedagogic approach we include an open section on unsolved problems, presented as exercises for the student. We also review varying constant models: the Brans‐Dicke theory, the Bekenstein varying α model, and several more radical ideas. We show how they make contact with strange high‐redshift data, and perhaps other cosmological puzzles. We conclude with a few remaining observational puzzles which have failed to make contact with quantum gravity, but who knows… We would like to thank Mario Novello for organizing an excellent school in Mangaratiba, in direct competition with a very fine beach indeed.
782(2005); http://dx.doi.org/10.1063/1.2032734View Description Hide Description
The detection of gravitational waves is one of the greatest challenges of modern physics. A range of noise sources limit the sensitivity of all gravitational wave detectors. To improve sensitivity and create advanced detectors that will enable gravitational wave astronomy to begin requires all the noise sources to be sufficiently suppressed. Photon noise reduction requires the use of high optical power. This in itself introduces new problem which are addressed in detail.
782(2005); http://dx.doi.org/10.1063/1.2032735View Description Hide Description
782(2005); http://dx.doi.org/10.1063/1.2032737View Description Hide Description
It has recently been suggested to represent functions on the sphere by a “ multipole vector decomposition ”, rather than by the usual spherical harmonic expansion. I recall the definition and main properties of the multipole vectors, as they were introduced in the literature. I show that they are related to the harmonic projection and to the Maxwell decomposition. This allows to deduce additional properties. I extend to complex polynomials.