Extra dimensions and Lorenz invariance violation

Astrophysics and Space Science, 2005

The observation of the time delay between the soft emission and the high-energy radiation from cosmological gamma ray bursts can be used as an important observational test of multi-dimensional physical theories. The main source of the time delay is the variation of the electromagnetic coupling, due to dimensional reduction, which induces an energy dependence of the speed of light. For photons with energies around 1 TeV, the time delay could range from a few seconds in the case of Kaluza-Klein models to a few days for models with large extra-dimensions. Based on these results we suggest that the detection of the 18-GeV photon ∼4500 s after the keV/MeV burst in GRB 940217 provides a strong evidence for the existence of extra-dimensions. The time delay of photons, if observed by the next generation of high energy detectors, like, for example, the SWIFT and GLAST satellite based detectors, or the VERITAS ground-based TeV gamma-ray instrument, could differentiate between the different models with extra-dimensions.

Physical Review D, 2013

A model in which pointlike defects are randomly embedded in Minkowski spacetime is considered. The distribution of spacetime defects is constructed to be Lorentz-invariant. It does not introduce a preferred reference frame, because it is based on a sprinkling process. A field-theoretic action for the photon and a fermion is set up, in which the photon is assumed not to couple to the defects directly, but via a scalar field. We are interested in signs for Lorentz violation caused by the spacetime defects, which are expected to reveal themselves in the photon sector. A modification of the photon dispersion relation may result as a quantum effect and we compute it at leading order perturbation theory.

Astroparticle Physics, 2003

Observations of the multi-TeV spectra of the nearby BL objects Mkn 421 and Mkn 501 exhibit the high energy cutoffs predicted to be the result of intergalactic annihilation interactions, primarily with infrared photons having a flux level as determined by various astronomical observations. After correction for this absorption effect, the derived intrinsic spectra of these multi-TeV sources can be explained within the framework of simple synchrotron self-Compton emission models. Stecker and Glashow have shown that the existence of such annihilations via electron-positron pair production interactions up to an energy of 20 TeV puts strong constraints on Lorentz invariance violation. Such constraints have important implications for Lorentz invariance violating (LIV) quantum gravity models as well as LIV models involving large extra dimensions. We also discuss the implications of observations of high energy γ-rays from the Crab Nebula on constraining quantum gravity models.

International Journal of Theoretical Physics, 2015

This paper deals with the violation of Lorentz symmetry. The approach is based on Compton scattering which becomes modified due to a modified dispersion relation arising from a minimum spacetime cut off as in modern Quantum Gravity approaches. With this amendment, we find that two high-energy rays of different energies develop a timelag. This time separation becomes prominent when the energies of the considered photons is ≥ 1GeV. Extending our approach to gamma rays of cosmic origin we predict that they undergo innumerable such scattering processes before reaching us. Therefore, it accounts for the time-lag phenomena of gamma ray bursts (GRB)'s which have been claimed to be observed. Also, we find that resorting to the modified Snyder-Sidharth Hamiltonian it is possible to extend the GZK cut off beyond its normal limit, 10 20 eV. Some observations of ultra high energy cosmic rays support this. This extends the limits of special theory of relativity.

Physics Letters A, 2004

We discuss the theoretical foundations and the results of a double slit diffraction-like experiment in the infrared range, aimed at finding departures from the classical predictions. We found indeed an anomalous behavior of such a photon system. Possible interpretations can be given in terms of either the existence of de Broglie-Bohm hollow waves associated to photons, and/or a breakdown of local Lorentz invariance (LLI). The findings of the present experiment do agree with the threshold behavior in energy and space, recently derived (on an experimental basis) for the LLI breaking effect. This leads us to put forward the intriguing hypothesis that the hollow wave is a deformation of the space-time (Minkowskian) geometry. Our experimental findings have been tested in crossed photon-beam experiments, whose preliminary results evidence an anomalous behavior in the photon-photon cross section and confirm the threshold behavior in energy and space of the effect we observed.

2013

a di Trieste camille.couturier@in2p3.fr Abstract: Arrival times of photons from four bright GRBs observed by Fermi-LAT have been analyzed in order to detect a possible Lorentz Invariance Violation (LIV), related to a non trivial dispersion of light in vacuum. No delays have been detected and strong limits on the Quantum Gravity (QG) energy scale: for linear dispersion we set tight constraints placing the QG energy scale above the Planck mass; a quadratic leading LIV effect is also constrained.

Physical Review D, 2012

All quadratic translation-and gauge-invariant photon operators for Lorentz breakdown are included into the Stueckelberg Lagrangian for massive photons in a generalized R ξ gauge. The corresponding dispersion relation and tree-level propagator are determined exactly, and some leadingorder results are derived. The question of how to include such Lorentz-violating effects into a perturbative quantum-field expansion is addressed. Applications of these results within Lorentzbreaking quantum field theories include the regularization of infrared divergences as well as the free propagation of massive vector bosons.

2010

The topic of Lorentz invariance violation (LIV) is a fundamental question in physics that has taken on particular interest in theoretical explorations of quantum gravity scenarios. I discuss various γ-ray observations that give limits on predicted potential effects of Lorentz invariance violation. Among these are spectral data from ground based observations of the multi-TeV γ-rays from nearby AGN, INTEGRAL detections of polarized soft γ-rays from the vicinity of the Crab pulsar, Fermi Gamma Ray Space Telescope studies of photon propagation timing from γ-ray bursts, and Auger data on the spectrum of ultrahigh energy cosmic rays. These results can be used to seriously constrain or rule out some models involving Planck scale physics. Possible implications of these limits for quantum gravity and Planck scale physics will be discussed.

Physical Review D, 2001

One of the most puzzling current experimental physics paradoxes is the arrival on Earth of Ultra High Energy Cosmic Rays (UHECRs) with energies above the GZK threshold (5×10 19 eV). Photopion production by CMBR photons should reduce the energy of these protons below this level. The recent observation of 20TeV photons from Mk 501 (a BL Lac object at a distance of 150Mpc) is another somewhat similar paradox. These high energy photons should have disappeared due to pair production with IR background photons. A common feature of these two paradoxes is that they can both be seen as "threshold anomalies": energies corresponding to an expected threshold (pion production or pair creation) are reached but the threshold is not observed. Several (relatively speculative) models have been proposed for the UHECR paradox. No solution has yet been proposed for the TeV-γ paradox. Remarkably, the single drastic assumption of a violation of ordinary Lorentz invariance would resolve both paradoxes. We present here a formalism for the systematic description of the type of Lorentz-invariance deformation (LID) that could be induced by non-trivial short-distance structure of space-time, and we show that this formalism is well suited for comparison of experimental data with LID predictions. We use the UHECR and TeV-γ data, as well as upper bounds on time-of-flight differences between photons of different energies, to constrain the parameter space of the LID. A model with only two free parameters, an energy scale and a dimensionless parameter characterizing the functional dependence on the energy scale, is shown to be sufficient to solve both the UHECR and the TeV-γ threshold anomalies while satisfying the time-of-flight bounds. The allowed region of the two-parameter space is relatively small, but, remarkably, it fits perfectly the expectations of the quantum-gravitymotivated space-time models known to support such deformations of Lorentz invariance: an integer value of the dimensionless parameter and a characteristic energy scale constrained to a narrow interval in the neighborhood of the Planck scale.

Journal of High Energy Astrophysics, 2018

We explore the possibility to geometrize the interaction of massive fermions with the quantum structure of space-time, trying to create a theoretical background, in order to explain what some recent experimental results seem to implicate on the propagation of Ultra High Energy Cosmic Rays (UHECR). We will investigate part of the phenomenological implications of this approach on the predicted effect of the UHECR suppression, in fact recent evidences seem to involve the modification of the GZK cut-off phenomenon. The search for an effective theory, which can explain this physical effect, is based on Lorentz Invariance Violation (LIV), which is introduced via Modified Dispersion Relations (MDRs). Furthermore we illustrate that this perspective implies a more general geometry of space-time than the usual Riemannian one, indicating, for example, the opportunity to resort to Finsler theory.