# index.php/en

From Particulas

The Particle and Fields group is involved in:

- National and international collaborations
- The Pierre Auger Observatory
- The Instituto Balseiro Diploma Programme
- Organization of national and international symposia and schools.
- Lecturing in a number of undergraduate and graduate courses: Classical Mechanics, Electromagnetism, Quantum Mechanics I, Quantum Mechanics II, Mathematics I, II and III, Group Theory, Introduction to Particle Physics, Field Theory I, Field Theory II, High Energy Physics, Physics Beyond the Standard Model, General Relativity, Gravitation and Field Theory, String Theory, Quantum Groups and Integrable Systems, Differential Manifolds, Conformal Field Theory, Astroparticle Physics.

**Our main research areas are:**

**Astroparticle and Cosmology**- Ultra High Energy Cosmic Rays

Research in this area takes place at very exciting times, marked by the first years of operation of the Pierre Auger Observatory. Its measurements are expected to shed light into the enigma posed by the most energetic cosmic rays, revealing their composition, place of origin, acceleration mechanisms and propagation effects through the cosmos.

The Particle Physics group has an active role in the experimental aspects of the Auger project. It contributes to the characterization, construction, calibration and operation of its surface detectors. The group is also involved in theoretical studies of cosmic ray propagation and in the development of statistical tools for their analysis. The Observatory is already in a stage of data acquisition, and work in its analysis and interpretation is of fundamental importance.

Completion of the Observatory construction is expected by the end of 2007, and several options are under analysis to enhance its future capabilities. Among them, addition of muon counters will enhance its ability to identify the chemical composition of the primary cosmic rays, a denser sub-array of Cherenkov surface detectors will allow to explore a lower energy range (10^{17}eV to 3x10^{18}eV), an array of radio-antenas will provide an alternative method to detect cosmic rays, and atmospheric fluorescence at higher altitude (lower energies) will be possible.

For additional information visit the dedicated webpage in our server. - Gamma Ray Bursts

Gamma Ray bursts (GRBs) are extremely violent astrophysical events. They are known to have extragalactic origin, but there is still great uncertainty about the mechanism that originates them. The Particle Physics group has recently become involved in experimental activity related to detection of GRBs. The LAGO project aims to detect GRBs with water Cherenkov detectors similar to the surface detectors of the Pierre Auger Observatory but located at very high altitude. A first prototype detector, equipped with instrumentation provided by the Pierre Auger project, is under test at the Centro Atómico Bariloche.

Additional information is available in a dedicated webpage of our server. - Cosmology

Research in this area concentrates on the interpretaion of recent measurements, particularly those of anisotropy of temperature and polarization of the cosmic microwave background radiation and of weak gravitational lensing effects, that made possible to determine the values of the most relevant cosmological parameters with high precision. Alternative sources of polarization of the cosmic microwave background are analysed, and the possibility that their imprints may allow indirect detection of gravitational waves and primordial magnetic fields.

Another research subject is the origin of the matter-antimatter asimmetry, particularly the scenarios based on leptogenesis, which is at present the favorite. CP violation processes and the impact of supersymmetry upon these scenarios are subject of detailed analyses. - Neutrinos in Supernovae

Another area of research is that of neutrino emission in supernovae, which constitute their dominant energy loss mechanism (they carry 99% of the energy output). Densities duringthe first few seconds as a neutron star forms are suficciently high that neutrinos are confined. In this neutrinosphere several processes take place that have significant observable consequences upon the evolution of the protostar, and provide information both on its structure as well as on the neutrino physics itself. The protostar becomes a laboratory under extreme conditions. The research project concentrates in the relation between observed pulsar (neutron stars) kicks and resonant oscillation of neutrinos inside the neutrinosphere, permeated by the extraordinarily intense magnetic fields present in the protostars.

- Ultra High Energy Cosmic Rays

**String Theory**

String Theory is considered the most promising candidate for a quantum theory of gravity. Einstein's general relativity emerges as a low energy limit, below a typical, Estring, along with gauge interactions and chiral fermions, which are the basic constituents in the formulation of the Standard Model of elementary particles. String theory provides also a consistent formulation that encompasses several ingredients that appear in many extensions of the Standard Model that have been put forward.

String Theory constitutes in turn a frame in which several fundamental questions can be addressed, such as the paradox of information loss in black hole evaporation, the origin of chirality, the origin of the number of generations, etc. At present there is no closed formulation for string theory and several aspects, such as its behaviour in non-perturbative regimes, are only partially known.

Research on string theory within the Bariloche group has focused mostly in the so called*string phenomenology*, which aims to understand the way in which particle physics (the Standard Model and its possible extensions) are embedded withing string theory.**Field Theory**- Field Theory applied to problems in Condensed Matter and the Quantum Hall effect.

Theoretical studies are under way of Condensed Matter systems that are most naturally described by methods of Quantum Field Theory. Phenomenology of such systems usually involves excitations (*quasiparticles*) with properties and interactions that are common in High-Energy physics, and require application of novel ideas. Examples of such systems are the Quantum Hall effect (and uncompressible fluids in general), High Critical Temperature Superconductors, and vortex dynamics. - Field Theory in curved space time and potential violations to relativity.

Possible violations to Lorentz symmetry by low energy quantum gravity effects are explored. Notwithstanding the fact that the characteristic scale for quantum gravity is Planck energy, observable effects can occur at much lower energy and manifest as modifications in dispersion relations, that could be interpreted in terms of a violation of Lorentz symmetry. They would have consequences in a variety of phenomena, including changes in reaction thresholds, fields generation and propagation, etc. Its detection would provide hints of the underlying quantum gravity properties.

At present, we carry on research on the effects of these perturbations upon electromagnetic radiation. The effective low energy theory leads to modified Maxwell equations in which vacuum behaves as a dispersive medium, with birefringent properties, Cherenkov radiation, anisotropies and distortions in the spectral distribution of radiation. Given that supernova remnants, gamma ray bursts and other astronomical objects show evidence of synchrotron radiation of photons with energy up to at least a few TeVs, there is the possibility to observe in them a violation of Lorentz symmetry and evidences on quantum aspects of gravity.

- Field Theory applied to problems in Condensed Matter and the Quantum Hall effect.
**Mathematic Physics**

We consider the formulation in precise mathematical terms of several physics models. They include Classification of rational conformal theories in two dimensions and their relationship to weak Hopf algebras. Quantum symmetries of associate graphs. Witten-Wess-Zumino models and reconstruction theorem. Geometry of dynamical systems. Structure of simplectic grupoids in symmetries and dualities. Generalization of Poisson structures. Dimensional regularization and non-commutative geometry.**Beyond the Standard Model**

The Standard Model is the theory that describes the fundamental particles and their interactions. Its predictive power has been tested with an impressive accuracy. However there are several experimental and theoretical reasons that suggest that the Standard Model is not the ultimate theory of nature. Some examples are the lack of explanations for the following phenomena: neutrino masses, the matter-antimatter asymmetry and dark matter, as well as the the lack of fundamental descriptions of: a quantum theory of gravity and the origin and hierarchy of the masses of the fundamental particles. There are several experiments designed to discover the nature of these phenomena, like the Large Hadron Collider at CERN, Geneva. There are also a number of theories aiming to solve these problems, they are called theories Beyond the Standard Model, including new particles and interactions, strongly coupled theories, supersymmetry and extra-dimensions, among others.

Our group is involved in the study of theoretical and phenomenological aspects of theories Beyond the Standard Model. Models describing a composite Higgs and theories with extra dimensions can solve the hierarchy problem, as well as the flavor problem, predicting towers of new particles with TeV masses. We also study the phenomenology of these particles at Tevatron and LHC to find the best channels for their discovery in the present high energy accelerators.