I.C.R.A. Network - Talks Pescara 2013

Talks Pescara 2013

Presentations can be found here

List of talks with abstracts

G. A. Alekseev (Steklov Mathematical Institute of the Russian Academy of Sciences, Moscow)

Kerr and Kerr-Newman black holes in Mathematical General Relativity

A large variety of discoveries in the modern gravitational theory where made due to a knowledge of exact black hole solutions -- Schwarzschild and Reissner-Nordstr\"om solutions at first and then, about 50 year later, of Kerr, Kerr-NUT and Kerr-Newman solutions. During the next 50 years which passed now from the R.Kerr's discovery of the rotating black hole solution different branches of ``mathematical theory'' of black holes had been developed:
a) various geometrical features of an isolated black hole space-times (existence and structure of horizons, ergospheres and singularities, the complete analytical extensions and structure of geodesics) as well as the dynamics of particles and fields on these backgrounds had been studied;
b) developed perturbation theory allowed to study (in the linear approximation, at least) the backward influence of particle and field dynamics on the black hole background, to prove the uniqueness of Kerr and Kerr-Newman solutions, to formulate the laws of black hole thermodynamics, to analyse numerous aspects of radiation and propagation of fields in these space-times;
c) application of powerful ideas of the modern theory of integrable nonlinear systems to Einstein and Einstein - Maxwell equations gave rise to discoveries of various solution generating methods which allow to construct the exact solutions for Schwarzschild, Reissner-Nordstrom, Kerr and Kerr-Newman black holes interacting with various external fields and to analyze (though for very idealized models, but in exact, non-perturbative form) the character of this interactions in the arbitrary strong field regimes.
In the present communication, we concentrate on the last two of the above points and describe the soliton nature of Kerr and Kerr-Newman black holes discovered in the framework of inverse scattering approach to vacuum and electrovacuum fields (Belinski and Zakharov - 1978 and GA-1980 respectively). As a new example, an exact electrovacuum solution which describes a charged black hole immersed into the external asymptotically homogeneous electric field -- the Bertotti-Robinson universe which possess a non-trivial space-time topology ($AdS_2\times S_2$) will be presented and the most interesting properties of this solution will be described.

Victor Berezin (Institute for Nuclear Research of the Russian Academy of Sciences, Moscow)

Quantum black holes and their classical analogs

It is shown that the quantization of the self-gravitating spherically symmetric thin dust shells leads to the stationary Schroedinger-like equations in finite differences. The method is elaborated for extracting the discrete mass (energy) spectra without solving the wave equations but using, instead, the analytical properties of the "correct" solutions and non-trivial causal structure of the geodesically complete space-times. The quantum state of the shell depends on two quantum numbers. This feature suggests that the quantum black hole is the special point in the spectrum obeying the .no-memory.condition. Being translated into the classical language, such a condition allows us to construct the purely classical model possessing the temperature. By using self-consistently the Einstein equations and classical (local) thermodynamics it becomes possible to explain the log3-puzzle.

Brane Universe: Global Geometry

The global geometries of bulk vacuum space-times in the brane-universe models are investigated and classiﬁed in terms of geometrical invariants. The corresponding Carter-Penrose diagrams and embedding diagrams are constructed. It is shown that for given energy-momentum induced on the brane there can be diﬀerent types of global geometries depending on the signs of a bulk cosmological term and surface energy density of the brane (the sign of the latter does not inﬂuence the internal cosmological evolution). It is shown that in the Randall-Sundrum scenario it is possible to have an asymmetric hierarchy splitting even with a Z2-symmetric matching of ”our” brane to the bulk.

Donato Bini (Istituto per le Applicazioni del Calcolo, CNR, Roma, Italy)

Poynting-Robertson-like effects in general relativity: I Black hole solutions

Poynting-Robertson-like effects in general relativity: II Gravitational wave and cosmological solutions

A review of friction-force effects for motion of test particles scattering electromagnetic or gravitational radiation are discussed. Special attention is devoted to black hole, gravitational wave and cosmological spacetimes.

Johannes Bluemlein (Deutsches Elektronen-Synchrotron, DESY)

Mathematical Structures of Feynman Integrals: Harmonic Sums, Polylogarithms and Zeta Values

TBD

Generalized Harmonic Sums, Cyclotomic Sums, nested Sums with Binomial Weights

TBD

Sandip K. Chakrabarti (Indian Centre For Space Physics, India)

Latest Developments in the Accretion Processes Around Black Holes

I discuss the latest developments in the subject of the accretion processes around black holes. This includes: (a) To show that the black holes accrete with two components, one is Keplerian and the other is low-angular momentum, sub-Keplerian flow, (b) To show with hydrodynamic simulations that the two component flow is stable; (c) To show that low and intermediate frequency QPOs are the results of the resonance oscillations of the Centrifugal barrier dominated boundary layer of the black hole and (d) To incorporate a new tool in the XSPEC analysis tool for NASA satellite data to extract information about the accretion rates of the two components and the location of the centrifugal barrier.

Detections of Gamma-ray-bursts and soft gamma-ray repeaters using very low frequency radio waves

This detection is mainly the detection of the change in ionospheric electron densities through the change in reflection coefficients of the ionosphere.

Formation of complex prebiotic molecules during star formations and their delivery to earth through meteorites

TBD

Chemical Evolution of the Universe and the origin of Life

Popular level talk for PhD students

A. Di Piazza (Max-Planck-Institut for Kernphysik)

Tests of strong-field classical and quantum electrodynamics with intense laser fields

Classical electrodynamics (CED) and quantum electrodynamics (QED) are well established theories and have been tested experimentally in different regimes. However, there are still areas of CED and QED that deserve theoretical and experimental investigation. In view of the increasingly stronger available laser fields it is becoming feasible to employ them totest CED and QED under the extreme conditions supplied by ultra-intense fields [1]. A fundamental problem in CED is the so-called "radiation reaction" problem: classically, when a charged particle (an electron, for deniteness) is accelerated by an external field, it emits radiation and this emission changes the motion of the electron. In the realm of CED, the so-called Landau-Lifshitz (LL) describes the motion of an electron by including the effects of radiation reaction [2] and it has not yet been tested experimentally. Recent attempts to test the LL equation by employing ultra-intense laser fields are reported, based in the possibility of measuring the energy spectrum of the radiation emitted by laser-driven electron beams. What is the quantum analog of radiation reaction? We answer this question in the realm of strong-field QED [3], by connecting radiation reaction to the emission by an electron of many photons, and we show the existence of the so-called quantum radiation dominated regime, in which quantum recoil and radiation reaction effects both dominate the dynamics of the electron.
Finally, other aspects of strong-field QED like the alterations of the properties of the vacuum under the effects of strong background electromagnetic fields, electron-positron pair production and the related development of QED cascades are reviewed [1].
[1] A. Di Piazza et al., Rev. Mod. Phys. 84, 1177 (2012).
[2] L. D. Landau and E. M. Lifshitz, The Classical Theory of Fields - Fourth Edition,
(Elsevier, Oxford, 1975).
[3] V. B. Berestetskii, E. M. Lifshitz, and L. P. Pitaevskii, Quantum Electrodynamics - 2nd Ed. (Elsevier, Oxford, 1982).

Gabriele Gionti (Vatican Observatory)

TBD

The aim of this talk is to provide a brief description of the topics we are investigating with my collaborators.
I will start giving some examples of duality in field theory starting with the electro-magnetic field and continuing with the scalar field.
In a pedagogical way, I will mention the problem of closed string compactification highlighting the emergence of T-Duality as an exact symmetry of the spectrum. I will pose the problem of implementing T-duality as a explicit symmetry of the starting Lagrangian. We will show, explicitly, the toy-model example of the scalar field compactified on a circle. We will explore all the interesting feature, which emerge from this model since, in our opinion, are the same that emerge in the case of String Theory. In particular we will show that the presence, in a T-Duality invariant theory, of second class constraints (using Dirac's constraint theory language) implies the emergence of non commutative filed at quantum level.
We will mention how these reasoning, for the scalar field on a circle, can be implemented in the case of String Theory compactified on Tori. The T-Duality symmetry here will be more complicated and opens the theory to new investigation in mathematics as well as in physics.
We will end mentioning that T-Duality can be used for deriving low energy limit amplitude, which gives natural modifications of Einstein General Relativity. These modifications, we aim, could shed light on the subject of Dark Matter and Dark Energy.

Philippe Jetzer (Institute of Theoretical Physics, University of Zurich)

20 years of Gravitational Microlensing

I will give an overview of the results obtained so far by gravitational microlensing. In particular I will discuss the microlensing probability for different targets such as the galactic bulge, LMC, SMC and the Andromeda galaxy as well as give a review of the present status of microlensing searches conducted by the various collaborations in particular with respect to the problem of the galactic dark matter content in form of MACHOs.

Bruno Leibundgut (European Southern Observatory)

Supernova 1987A - spectacular physics

The explosion of SN 1987A has provided us with the opportunity to learn more about core collapse supernovae than with any other event. The evolution of this object has been followed in great detail with all available observing facilities and delivered an unprecedented record of this explosion. There are many unique observations of this object: the neutrino burst indicating the collapse to a neutron star, the early evolution giving evidence that the progenitor star was a compact blue giant star and that there must have been significant mixing of the elements within the explosion, the circumstellar ring - presumably a remnant of the stellar evolution of the progenitor star, the formation of dust in the ejecta, and the shock interaction of the supernova ejecta with its surrounding. SN 1987A is the first supernova, where we can observe the inner ejecta directly and can also follow the effects of shocks on the ring and the ejecta. I will present the history of this unique event and the latest results showing how the supernova has entered a new phase.

Supernova Cosmology

The remarkable discovery of an accelerating expansion of the Universe is based on the observations of distant supernovae. SNe Ia, presumably thermonuclear explosions, have been employed for this measurements. A careful analysis and understanding of the supernova physics is required to fully appreciate the use of these events as distance indicators. I will present the role SNe Ia have played in the past and now for determining the cosmological parameters.

Feng Longlong (University of Science/Technology Centre for Astrophysics, Hefei. China)

Phase variation of spinning particles in Kerr spacetime

Nikolaos Mavromatos (King's College London, Univ. of London)

Massive Right-handed Neutrinos in non-standard torsionful Geometries of the Early Universe: Matter-Antimatter asymmetry and role in Galactic Structure

I will describe the field theory of massive neutrino fields (left and right-handed ones, in extensions of the standard model) in non-standard, non-spherically symmetric (and thus Lorentz-violating) background geometries with torsion which may characterize the early Universe and how the latter can induce CPT-Violating asymmetries in the dispersion relations of fermions versus antifermion and thus the observed matter-antimatter asymmetry in the Universe. Cases of interest here include the propgation of neutrinos in: (i) populations of rotating (Kerr) black holes, (ii) (string-inspired) gravitational models in four space-time dimensions, in which a spin-one antisymmetric (Kalb-Ramond (KR)) field provides (via its field strength) the torsion. In four dimensions the KR field corresponds to a pseudoscalar degree of freedom (KR axion). Specific (string) backgrounds of cosmological interest imply in the latter case a constant torsion, which in turn results in CPT-Violating types of dispersion relations for fermions in such geometries, which are different from those of the antifermions, by terms proportional to the constant torsion. I emphasize the specific role of neutrinos, and in particular right-handed ones, on inducing Leptogenesis at early epochs of such Universes via neutrino/antineutrino oscillations that can occur in the presence of torsion. This Lepton-antilepton asymmetry then is communicated to the baryon sector by baryon-minus-lepton-(B-L)-number conserving sphaleron processes in the Standard-Model sector. Fluctuations of the torsion may also be responsible for yielding Majorana neutrino masses through anomalous graphs in the field theory involving Yukawa couplings of the Majorana neutrinos with ordinary axion fields that mix with the KR axion. There also seems to be another important role of the massive right-handed neutrinos, that of dark matter, if their masses are in the keV region, which in turn may also be linked to their important contribution to the structure formation of galaxies. The latter part (in collaboration with Ruffini, Arguelles and Rueda) will be discussed briefly, as more extensive discussion will be provided in the talk by C. Arguelles.

Hermann Nicolai (Max Planck Institute for Gravitational Physics)

The conformal Standard Model

TBD

Paolo Padovani (European Southern Observatory)

Active Galactic Nuclei

I will review the class of Active Galactic Nuclei (AGN), starting from the discovery of quasars fifty years ago and discussing their main properties and in particular the source of their huge powers. I will then describe how one determines AGN masses and their relevance to their physical evolution. I will then illustrate the many AGN classes and introduce the so-called "Unified Schemes", which allow us to drastically reduce the number of intrinsically different types of sources. I will then conclude with the relevance of AGN for galaxy evolution.

The deep radio sky

After reviewing the various classes of objects, which make up the radio sky, I will present some recent results on the sub-mJy source populations based on the Chandra Deep Field South VLA survey, with some details on their evolution and luminosity functions. I will then present the solution to a problem, which has been unsolved since the discovery of quasars in 1963, that is the mechanism responsible for radio emission in radio-quiet active galactic nuclei. I will put things into perspective by providing also the "big picture". Finally, the relevance of our results to future, deeper radio surveys, including those with the Square Kilometre Array, will be discussed.