259 research outputs found
CPT Violation: What and where to look for
In this review I classify the possible ways of CPT violation, and I describe
briefly their phenomenology, in both terrestrial and astrophysical experiments,
including antimatter factories, neutral mesons and neutrinos, and discuss the
various sensitivities. I also pay attention to disentangling genuine
quantum-gravity induced CPT violation from `fake' violation due to ordinary
matter effects. A particularly interesting situation arises when the breaking
of CPT invariance is through unitarity violations, in the sense of the matter
theory being viewed as an effective field theory, entangled with decoherening
quantum gravity ``environments''. In such a case the quantum mechanical CPT
operator is ill defined due to another mathematical theorem, and one has novel
effects associated with CPT Violating modifications of Einstein-Podolsky-Rosen
type correlations of entangled meson states in B and phi meson factories.Comment: 9 pages, latex, uses special macros, Invited plenary talk in LEAP05,
16-22 May 2005, Bonn/GSI and Julich, German
Some Aspects of String Cosmology and the LHC
I discuss some (unconventional) aspects of String Cosmology of relevance to
supersymmetric dark matter searches at the Large Hadron Collider (LHC) at CERN.
In particular, I analyse the role of time-dependent dilaton fields in relaxing
some of the stringent constraints that characterise minimal supersymmetric
models in standard cosmology. I also study briefly CPT-violating aspects of
brane Universe models with space-time brane defects at early epochs and their
potential relevance to the observed Baryon Asymmetry.Comment: 12 pages pdflatex, uses special macros.Plenary talk at the 1st
International Conference on New Frontiers in Physics 2012, Kolymbari (Crete,
Greece), June 10-16 2012, to appear in the Proc. EPJ WEB of Conferences,
updated reference
Matter-Antimatter Asymmetry in the Universe via String-Inspired CPT Violation at Early Eras
In four-space-time dimensional string/brane theory, obtained either through
compactification of the extra spatial dimensions, or by appropriate restriction
to brane worlds with three large spatial dimensions, the rich physics potential
associated with the presence of non-trivial Kalb-Ramond (KR) axion-like fields
has not been fully exploited so far. In this talk, I discuss a scenario whereby
such fields produce spontaneous Lorentz- and CPT-violating cosmological
backgrounds over which strings propagate, which in the early Universe can lead
to Baryogenesis through Leptogenesis in models with heavy right-handed
neutrinos.Comment: 6 pages Latex, one figure, uses special macros; Invited talk at the
International Workshop on CPT and Lorentz Symmetry in Field Theory,
University of the Algarve, Faro (Portugal), July 6-7 2017. To appear in the
Proceedings (Journal of Phys. Conf. Series (IOP)
Quantum-Gravity Induced Lorentz Violation and Dynamical Mass Generation
In Ref. [1] (by J. Alexandre) a minimal extension of (3+1)-dimensional
Quantum Electrodynamics has been proposed, which includes Lorentz-Violation
(LV) in the form of higher-(spatial)-derivative isotropic terms in the gauge
sector, suppressed by a mass scale . The model can lead to dynamical mass
generation for charged fermions. In this article I elaborate further on this
idea and I attempt to connect it to specific quantum-gravity models, inspired
from string/brane theory. Specifically, in the first part of the article, I
comment briefly on the gauge dependence of the dynamical mass generation in the
approximations of [1], and I propose a possible avenue for obtaining the true
gauge-parameter-independent value of the mass by means of Pinch Technique
argumentations. In the second part of the work I embed the LV QED model into
multibrane world scenarios with a view to provide a geometrical way of
enhancing the dynamical mass to phenomenologically realistic values by means of
bulk warp metric factors, in an (inverse) Randall-Sundrum hierarchy. Finally in
the third part of this note, I demonstrate that such Lorentz Violating QED
models may represent parts of a low-energy effective action (of
Finsler-Born-Infeld type) of open strings propagating in quantum D0-particle
stochastic space-time foam backgrounds, which are viewed as consistent quantum
gravity configurations.Comment: 34 pages latex, uses special macros (axodraw), three eps figures
incorporate
Theoretical and Phenomenological Aspects of CPT Violation
I review briefly various models and ways of Quantum-Gravity induced CPT
violation, and discuss in some detail their phenomenology, in particular
precision CPT tests in neutral mesons, and hydrogen/antihydrogen spectroscopy.
As I shall argue, severe constraints can be placed in CPT violating parameters,
with sensitivities that can safely exclude models with effects suppressed by a
single power of Planck mass.Comment: 9 pages latex, Invited talk, LEAP03, Yokohama (Japan), 3-7 March
2003, Proc. Nucl. Instr. Methds. to appea
Pseudoscalar Fields in Torsionful Geometries of the Early Universe, the Baryon Asymmetry and Majorana Neutrino Mass Generation
We discuss here a specific field-theory model, inspired from string theory,
in which the generation of a matter-antimatter asymmetry in the Cosmos is due
to the propagation of fermions in a non-trivial, spherically asymmetric (and
hence Lorentz violating) gravitational background that may characterise the
epochs of the early universe. The background induces different dispersion
relations, hence populations, between fermions and antifermions, and thus CPT
Violation (CPTV) already in thermal equilibrium. Species populations may freeze
out leading to leptogenesis and baryogenesis. More specifically, after
reviewing some generic models of background-induced CPTV in early epochs of the
Universe, we consider a string-inspired scenario, in which the CPTV is
associated with a cosmological background with torsion provided by the
Kalb-Ramond (KR) antisymemtric tensor field of the string gravitational
multiplet. In a four-dimensional space time this field is dual to a
pseudoscalar ``axion-like'' field. The thermalising processes in this model are
(right-handed) Majorana neutrino-antineutrino oscillations, which are induced
in the presence of the KR axion background. These processes freeze out at a
(high) temperature , where is the Majorana neutrino mass, at
which the KR background goes to zero or is diminished significantly, through
appropriate phase transitions of the (string) universe. An additional, but
equally important, r\^ole, of the KR field is that its quantum fluctuations and
mixing with an ordinary axion, which couples to the Majorana neutrinos via
appropriate Yukawa couplings, can also lead to the generation of a Majorana
neutrino mass through quantum anomalies. This provides a novel way for
generating neutrino masses, independent of the traditional seesaw mechanism.Comment: 14 pages bibtex, one eps figure incorporated, uses special macros;
Invited plenary talk at XIV Mexican Workshop on Particles and Fields,
November 25-29 2013, Oaxaca (Mexico
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