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Luis Gonzalez-Mestres

Publications and source records attributed to Luis Gonzalez-Mestres.

At least 37 records · Page 2Linked to original sources
arXiv2002

Deformed Lorentz Symmetry and High-Energy Astrophysics (III)

Lorentz symmetry violation (LSV) can be generated at the Planck scale, or at some other fundamental length scale, and naturally preserve Lorentz symmetry as a low-energy limit (deformed Lorentz symmetry, DLS). DLS can have important implications for ultra-high energy cosmic-ray physics (see papers physics/0003080 - hereafter referred to as I -, astro-ph/0011181 and astro-ph/0011182, and references quoted in these papers). A crucial question is how DLS can be extended to a deformed Poincaré symmetry (DPS), and what can be the dynamical origin of this phenomenon. In a recent paper (hep-th/0208064, hereafter referred to as II), we started a discussion of proposals to identify DPS with a symmetry incorporating the Planck scale (like doubly special relativity, DSR) and suggested new ways in similar directions. Implications for models of quadratically deformed relativistic kinematics (QDRK) and linearly deformed relativistic kinematics (LDRK) were also discussed. We pursue here our study of these basic problems, focusing on the possibility to relate deformed relativistic kinematics (DRK) to new space-time dimensions and compare our QDRK model, in the form proposed since 1997, which the Kirzhnits-Chechin (KCh) and Sato-Tati (ST) models. It is pointed out that, although the KCh model does not seem to work such as it was formulated, our more recent proposals can be related to suitable extensions of this model generalizing the Finsler algebras (even to situations where a preferred physical inertial frame exists) and using the Magueijo-Smolin transformation as a technical tool.

hep-th↗
arXiv2002

Deformed Lorentz Symmetry and High-Energy Astrophysics (II)

Lorentz symmetry violation (LSV) can be generated at the Planck scale, or at some other fundamental length scale, and naturally preserve Lorentz symmetry as a low-energy limit (deformed Lorentz symmetry, DLS). DLS can have important implications for ultra-high energy cosmic-ray physics (see papers physics/0003080, astro-ph/0011181 and astro-ph/0011182, and references quoted in these papers). A crucial question is how DLS can be extended to a deformed Poincare symmetry (DPS), and what can be the dynamical origin of this phenomenon. We discuss recent proposals to identify DPS with a symmetry incorporating the Planck scale (doubly special relativity, DSR) and suggest new ways in this direction. Implications for models of quadratically deformed relativistic kinematics (QDRK) and linearly deformed relativistic kinematics (LDRK) are also discussed.

hep-th↗
arXiv2000

Lorentz Symmetry Violation and Acceleration in Relativistic Shocks

In previous papers (e.g. physics/0003080 and references therein), it was pointed out that Lorentz symmetry violation (LSV) at Planck scale can play a crucial role in astrophysical processes at very high energy. It can potentially inhibit radiation under external forces (e.g. synchrotron-like), GZK-like cutoffs, decays, photodisintegration of nuclei, momentum loss trough collisions (e.g. with a photon wind in reverse shocks), production of lower-energy secondaries... An updated description of this phenomenon is presented, focusing on acceleration in relativistic shocks and having in mind a model where the effective parameter driving LSV would vary like the square of the momentum scale (Quadratically Deformed Relativistic Kinematics, QDRK). Implications for ultra-high energy (UHE) neutrino production are equally discussed.

astro-ph↗
arXiv2000

Gamma and Cosmic-Ray Tests of Special Relativity

Lorentz symmetry violation (LSV) at Planck scale can be tested (see e.g. physics/0003080) through ultra-high energy cosmic rays (UHECR). In a deformed Lorentz symmetry (DLS) pattern where the effective LSV parameter varies like the square of the momentum scale (quadratically deformed relativistic kinematics, QDRK), a 10E-6 LSV at Planck scale would be enough to produce observable effects on the properties of cosmic rays at the 10E20 eV scale: absence of GZK cutoff, stability of unstable particles, lower interaction rates, kinematical failure of any parton model and of standard formulae for Lorentz contraction and time dilation... Its phenomenological implications are compatible with existing data. If the effective LSV parameter is taken to vary linearly with the momentum scale (linearly deformed relativistic kinematics, LDRK), a LSV at Planck scale larger than 10E-7 eV seems to lead to contradictions with data above TeV energies. Consequences are important for high-energy gamma-ray experiments, as well as for high-energy cosmic rays and gravitational waves.

astro-ph↗
arXiv1999

The Luminescent Bolometer As a Dark Matter Detector

Direct detection of WIMP dark matter candidates has to face many difficult challenges. In particular, it requires an extremely high level of background rejection. The only way out seems to be particle identification which, for experiments based on nucleus recoil, is most efficiently performed by simultaneously detecting ionization or light and phonons. When comparing different approaches, it is necessary to keep in mind the potential requirement of building large detectors and the difficulties that this condition may raise for some cryogenic devices. It is claimed that the luminescent bolometer (simultaneous detection of light and phonons) red by arrays of superconducting tunnel junctions, as proposed by the author some years ago, ultimately provides the most appropriate WIMP detector. Solar neutrino detection and other applications are also briefly discussed.

hep-ex↗
arXiv1999

Deformed Lorentz Symmetry and Ultra-High Energy Cosmic Rays

Lorentz symmetry violation (LSV) is often discussed using models of the $THεμ$ type which involve, basically, energy independent parameters. However, if LSV is generated at the Planck scale or at some other fundamental length scale, it can naturally preserve Lorentz symmetry as a low-energy limit (deformed Lorentz symmetry, DLS). Deformed relativistic kinematics (DRK) would be consistent with special relativity in the limit $k$ (wave vector) $\to ~0$ and allow for a deformed version of general relativity and gravitation. We present an updated discussion of the possible implications of this pattern for cosmic-ray physics at very high energy. A $\approx ~10^{-6}$ LSV at Planck scale, leading to a DLS pattern, would potentially be enough to produce very important observable effects on the properties of cosmic rays at the $\approx \~10^{20} eV$ scale (absence of GZK cutoff, stability of unstable particles, lower interaction rates, kinematical failure of the parton model...). We compare our approach with more recent similar claims made by S. Coleman and S. Glashow from models of the $THεμ$ type.

hep-ph↗
arXiv1999

Superluminal Particles in Cosmic-Ray Physics

Present low-energy bounds on Lorentz symmetry violation do not allow to exclude the possible existence of superluminal particles (superbradyons) with critical speed in vacuum $c_i \gg c$ (c = speed of light) whose kinematical properties would be close to of "ordinary" particles (bradyons) apart from the difference in critical speed. If they exist, superbradyons may be the basic building blocks of vacuum and and matter at Planck scale, provide most of the matter in the Universe and be natural dark matter candidates. We present an updated discussion of their theoretical and experimental properties, especially as cosmic ray primaries or sources, as well as problems related to their possible direct detection.

hep-ph↗
arXiv1998

Lorentz symmetry violation at Planck scale, cosmology and superluminal particles

Although Lorentz symmetry has been tested at low energy with extremely good accuracy, its validity at very high energy is much less well established. If Lorentz symmetry violation (LSV) is energy-dependent (e.g. $\propto E^2$), it can be of order 1 at Planck scale and undetectable at GeV scale or below. Similarly, superluminal particles with positive mass and energy (superbradyons) can exist and be the ultimate building blocks of matter. We discuss a few cosmological consequences of such a scenario, as well as possible experimental tests.

physics.gen-ph↗
arXiv1997

Observing Air Showers from Cosmic Superluminal Particles

The Poincaré relativity principle has been tested at low energy with great accuracy, but its extrapolation to very high-energy phenomena is much less well established. Lorentz symmetry can be broken at Planck scale due to the renormalization of gravity or to some deeper structure of matter: we expect such a breaking to be a very high energy and very short distance phenomenon. If textbook special relativity is only an approximate property of the equations describing a sector of matter above some critical distance scale, an absolute local frame (the "vacuum rest frame", VRF) can possibly be found and superluminal sectors of matter may exist related to new degrees of freedom not yet discovered experimentally. The new superluminal particles ("superbradyons", i.e. bradyons with superluminal critical speed) would have positive mass and energy, and behave kinematically like "ordinary" particles (those with critical speed in vacuum equal to c, the speed of light) apart from the difference in critical speed (c_i >> c where c_i is the critical speed of a superluminal sector). They may be the ultimate building blocks of matter At speed v > c, they are expected to release "Cherenkov" radiation ("ordinary" particles) in vacuum. Superluminal particles could provide most of the cosmic (dark) matter and produce very high-energy cosmic rays. We discuss: a) the possible relevance of superluminal matter to the composition, sources and spectra of high-energy cosmic rays; b) signatures and experiments allowing to possibly explore such effects. Very large volume and unprecedented background rejection ability are crucial requirements for any detector devoted to the search for cosmic superbradyons. Future cosmic-ray experiments using air-shower detectors (especially from space) naturally fulfil both requirements.

physics.gen-ph↗
arXiv1997

Physics Opportunities Above the Greisen-Zatsepin-Kuzmin Cutoff: Lorentz Symmetry Violation at the Planck Scale

Special relativity has been tested at low energy with great accuracy, but these results cannot be extrapolated to very high-energy phenomena: this new domain of physics may actually provide the key to the, yet unsettled, question of the ether and the absolute rest frame. Introducing a critical distance scale, a, below 10E-25 cm (the wavelength scale of the highest-energy observed cosmic rays) allows to consider models, compatible with standard tests of special relativity, where a small violation of Lorentz symmetry (a can, for instance, be the Planck length) leads to a deformed relativistic kinematics (DRK) producing dramatic effects on the properties of very high-energy cosmic rays. For instance, the Greisen-Zatsepin-Kuzmin (GZK) cutoff does no longer apply and particles which are unstable at low energy (neutron, some hadronic resonances like the Delta++, possibly several nuclei...) become stable at very high energy. In these models, an absolute local rest frame exists (the vacuum rest frame, VRF) and special relativity is a low-momentum limit. We discuss the possible effects of Lorentz symmetry violation (LSV) on kinematics and dynamics, as well as the cosmic-ray energy range (well below the energy scale associated to the fundamental length) and experiments (on earth and from space) where they could be detected.

physics.gen-ph↗
arXiv1997

Luminescent Bolometer and Neutrino Physics

The luminescent bolometer, proposed in 1988, is now seriously considered for several applications in nuclear and particle physics: dark matter searches, double beta decays, low energy neutrino physics, heavy ion physics... It is also a very promising device for basic condensed-matter physics and chemistry experiments, and may lead to astrophysical applications. The luminescent bolometer is based on the simultaneous detection of light and phonons, allowing for particle identification and for a detailed study of the detector response. Digitized analysis of the signals produced in several sensors installed on the same crystal is then a very powerful tool. Superconducting sensors allow to detect the scintillation light pulse followed by the delayed front of phonons, and can be extremely sensitive leading to single photon counting in the visible range. They also provide information on the position of the event inside the absorber, and can be fast enough for all proposed applications. The luminescent bolometer, with superconducting sensors, appears extremely promising for real time $solar$ neutrino experiments based on new indium single crystal scintillators. We focus on this particular application, discussing the status of the art as well as open problems and presenting an updated description of a full scale real time solar neutrino experiment sensitive to the low energy sector. Other applications of the luminescent bolometer (e.g. spectroscopy or neutrino detection at reactors), involving indium compounds and other single crystal scintillators, are equally considered and discussed in detail.

physics.ins-det↗
arXiv1997

Lorentz Symmetry Violation, Vacuum and Superluminal Particles

If textbook Lorentz invariance is actually a property of the equations describing a sector of the excitations of vacuum above some critical distance scale, several sectors of matter with different critical speeds in vacuum can coexist and an absolute rest frame (the vacuum rest frame) may exist without contradicting the apparent Lorentz invariance felt by "ordinary" particles (particles with critical speed in vacuum equal to $c$, the speed of light). Sectorial Lorentz invariance, reflected by the fact that all particles of a given dynamical sector have the same critical speed in vacuum, will then be an expression of a fundamental sectorial symmetry (e.g. preonic grand unification or extended supersymmetry) protecting a parameter of the equations of motion. Furthermore, the sectorial Lorentz symmetry may be only a low-energy limit, in the same way as the relation $ω$ (frequency) = $c_s$ (speed of sound) $k$ (wave vector) holds for low-energy phonons in a crystal. We show that, in this context, phenomena such as the absence of Greisen-Zatsepin-Kuzmin cutoff and the stability of unstable particles at very high energy are basic properties of a wide class of noncausal models where local Lorentz invariance is broken introducing a fundamental length. Then, observable phenomena are produced at the wavelength scale of the highest-energy cosmic rays or even below this energy, but Lorentz symmetry violation remains invisible to standard low-energy tests. We discuss possible theoretical, phenomenological, experimental and cosmological implications of this new approach to matter and space-time, as well as prospects for future developments.

physics.gen-ph↗
arXiv1997

Lorentz Symmetry Violation and Superluminal Particles at Future Colliders

If textbook Lorentz invariance is actually a property of the equations describing a sector of the excitations of vacuum above some critical distance scale, several sectors of matter with different critical speeds in vacuum can coexist and an absolute rest frame (the vacuum rest frame) may exist without contradicting the apparent Lorentz invariance felt by "ordinary" particles (particles with critical speed in vacuum equal to $c$, the speed of light). Sectorial Lorentz invariance, reflected by the fact that all particles of a given dynamical sector have the same critical speed in vacuum, will then be an expression of a fundamental sectorial symmetry (e.g. preonic grand unification or extended supersymmetry) protecting a parameter of the equations of motion. Furthermore, the sectorial Lorentz symmetry may be only a low-energy limit, in the same way as the relation $ω$ (frequency) = $c_s$ (speed of sound) $k$ (wave vector) holds for low-energy phonons in a crystal. In this context, phenomena such as the absence of Greisen-Zatsepin-Kuzmin cutoff and the stability of unstable particles at very high energy are basic properties of a wide class of noncausal models where local Lorentz invariance is broken introducing a fundamental length. Observable phenomena from Lorentz symmetry violation and superluminal sectors of matter are expected at very short wavelength scales, even if Lorentz symmetry violation remains invisible to standard low-energy tests. We discuss signatures of this new physics at LHC and at other possible future colliders.

physics.gen-ph↗
arXiv1997

High-Energy Nuclear Physics with Lorentz Symmetry Violation

If textbook Lorentz invariance is actually a property of the equations describing a sector of the excitations of vacuum above some critical distance scale, several sectors of matter with different critical speeds in vacuum can coexist and an absolute rest frame (the vacuum rest frame) may exist without contradicting the apparent Lorentz invariance felt by "ordinary" particles (particles with critical speed in vacuum equal to $c$, the speed of light). Sectorial Lorentz invariance, reflected by the fact that all particles of a given dynamical sector have the same critical speed in vacuum, will then be an expression of a fundamental sectorial symmetry (e.g. preonic grand unification or extended supersymmetry) protecting a parameter of the equations of motion. Furthermore, the sectorial Lorentz symmetry may be only a low-energy limit, in the same way as the relation $ω$ (frequency) = $c_s$ (speed of sound) $k$ (wave vector) holds for low-energy phonons in a crystal. In this context, phenomena such as the absence of Greisen-Zatsepin-Kuzmin cutoff for protons and nuclei and the stability of unstable particles (e.g. neutron, several nuclei...) at very high energy are basic properties of a wide class of noncausal models where local Lorentz invariance is broken introducing a fundamental length. Observable phenomena are expected at very short wavelength scales, even if Lorentz symmetry violation remains invisible to standard low-energy tests. We present a detailed discussion of the implications of Lorentz symmetry violation for very high-energy nuclear physics.

nucl-th↗
arXiv1997

Possible Effects of Lorentz Symmetry Violation on the Interaction Properties of Very High-Energy Cosmic Rays

Special relativity has been tested at low energy with great accuracy, but these results cannot be extrapolated to the very high-energy region. Introducing a critical distance scale, $a$ , below 10E-25 cm (the wavelength scale of the highest-energy observed cosmic rays) allows to consider models, compatible with standard tests of special relativity, where a small violation of Lorentz symmetry ($a$ can, for instance, be the Planck length, around 10E-33 cm) produces dramatic effects on the interaction properties of very high-energy particles. Lorentz symmetry violation may potentially solve all the basic problems raised by the highest-energy cosmic rays (origin and energy, propagation...). Furthermore, superluminal sectors of matter may exist and release very high-energy ordinary particles or directly produce very high-energy cosmic-ray events with unambiguous signatures in very large detectors. We discuss these phenomena, as well as the cosmic-ray energy range (well below the energy scale associated to the fundamental length) and experiments where they could be detected and studied.

physics.gen-ph↗
arXiv1997

Lorentz Symmetry Violation and Very High-Energy Cross Sections

We discuss the implications of a recently proposed pattern of Lorentz symmetry violation on very high-energy cross sections. As a consequence of the breaking of local Lorentz invariance by the introduction of a fundamental length, $a$ , the kinematics is modified and the properties of final states are fundamentally different in collider-like (two incoming particles with equal, opposite momenta with respect to the vacuum rest frame) and fixed-target (one of the incoming particles at rest with respect to the vacuum rest frame) situations. In the first case, the properties of the allowed final states are similar to relativistic kinematics, as long as the relevant wave vectors are much smaller than the critical wave vector scale $a^{-1}$ . But, if one of the incoming particles is close to rest in the vacuum rest frame, energy conservation reduces the final-state phase space at very high energy and can lead to a sharp fall of cross sections starting at incoming-particle wave vectors well below the inverse of the fundamental length. Then, the Froissart bound may cease to be relevant, as total cross sections seem to become much smaller than it would be allowed by local, Lorentz-invariant, field theory. Important experimental implications of the new scenario are found for cosmic-ray astrophysics and for very high-energy cosmic rays reaching the earth.

physics.gen-ph↗