Dark Energy as an off-shell Tachyon Background in four-dimensional Strings (2009)
Alexandre, J., Mavromatos, N. E.
We consider a time-dependent bosonic string in graviton, dilaton and tachyon backgrounds, for which it was already shown that conformal invariance is respected to all orders in alpha' and in any...
Neutrino oscillations in a Robertson-Walker Universe with space time foam (2009)
Alexandre, J., Farakos, K., Mavromatos, N. E., Pasipoularides, P.
In Phys. Rev. D77 (2008) 105001, we have studied decoherence models for flavour oscillations in four-dimensional stochastically fluctuating space times and discussed briefly the sensitivity of...
Asymmetrically Warped Brane Models, Bulk Photons and Lorentz Invariance (2009)
Farakos, K., Mavromatos, N. E., Pasipoularides, P.
We present a brief review of our recent work [1] on asymmetrically warped brane models, where the background metric is characterized by different time and space warp factors. In particular we examine...
Probing a Possible Vacuum Refractive Index with Gamma-Ray Telescopes (2009)
Ellis, John, Mavromatos, N E, Nanopoulos, D V
We have used a stringy model of quantum space-time foam to suggest that the vacuum may exhibit a non-trivial refractive index depending linearly on gamma-ray energy: eta -1 ~ E_gamma/M_QG1, where...
Probing a Possible Vacuum Refractive Index with Gamma-Ray Telescopes (2009)
Ellis, John, Mavromatos, N. E., Nanopoulos, D. V.
We have used a stringy model of quantum space-time foam to suggest that the vacuum may exhibit a non-trivial refractive index depending linearly on gamma-ray energy: eta -1 ~ E_gamma/M_QG1, where...
Supersymmetry Signals of Supercritical String Cosmology at the Large Hadron Collider (2008)
Dutta, Bhaskar, Gurrola, Alfredo, Kamon, Teruki, Krislock, Abram, Lahanas, A. B., Mavromatos, N. E., ...
We investigate the minimal supergravity (mSUGRA) signals at the LHC in the context of supercritical string cosmology (SSC). In this theory, the presence of a time dependent dilaton provides us with a...
Bulk photons in Asymmetrically Warped Space-times and Non-trivial Vacuum Refractive Index (2008)
Farakos, K., Mavromatos, N. E., Pasipoularides, P.
We consider asymmetrically warped brane models, or equivalently brane models where the background metric is characterized by different time and space warp factors. The main feature of these models is...
Derivation of a Vacuum Refractive Index in a Stringy Space-Time Foam Model (2008)
Ellis, Jonathan Richard, Mavromatos, N E, Nanopoulos, D V
It has been suggested that energetic photons propagating in vacuo should experience a non-trivial refractive index due to the foamy structure of space-time induced by quantum-gravitational...
Derivation of a Vacuum Refractive Index in a Stringy Space-Time Foam Model (2008)
Ellis, John, Mavromatos, N. E., Nanopoulos, D. V.
It has been suggested that energetic photons propagating in vacuo should experience a non-trivial refractive index due to the foamy structure of space-time induced by quantum-gravitational...
Non-renormalization for the Liouville wave function (2008)
Alexandre, J., Kostouki, Anna, Mavromatos, N. E.
Using an exact functional method, within the framework of the gradient expansion for the Liouville effective action, we show that the kinetic term for the Liouville field is not renormalized.
Probing Quantum Gravity using Photons from a Mkn 501 Flare Observed by MAGIC (2008)
Albert, J., Ellis, John, Mavromatos, N. E., Nanopoulops, D. V., Sakharov, A. S., Sarkisyan, E. K. G., ...
We use the timing of photons observed by the MAGIC gamma-ray telescope during a flare of the active galaxy Markarian 501 to probe a vacuum refractive index ~ 1-(E/M_QGn)^n, n = 1,2, that might be...
Erratum (astro-ph/0510172): Robust Limits on Lorentz Violation from Gamma-Ray Bursts (2007)
Ellis, Jonathan Richard, Mavromatos, N E, Nanopoulos, D V, Sakharov, Alexander S, Sarkisyan-Grinbaum, E
We correct the fitting formula used in refs. [1,2] to obtain a robust limit on a violation of Lorentz invariance that depends linearly on the photon energy. The correction leads to a slight increase...
Neutrino oscillations in a stochastic model for space-time foam (2007)
Alexandre, J., Farakos, K., Mavromatos, N. E., Pasipoularides, P.
We study decoherence models for flavour oscillations in four-dimensional stochastically fluctuating space times and discuss briefly the sensitivity of current neutrino experiments to such models. We...
Theory from World-Sheet Defects in Liouville String (2007)
John Ellis, N.E. Mavromatos, D.V. Nanopoulos
We have argued previously that black holes may be represented in a D-brane approach by monopole and vortex defects in a sine-Gordon field theory model of Liouville dynamics on the world sheet....
Albert, J, Aliu, E, Anderhub, H, Antonelli, L A, Antoranz, P, Backes, M, ...
We use the timing of photons observed by the MAGIC gamma-ray telescope during a flare of the active galaxy Markarian 501 to probe a vacuum refractive index ~ 1-(E/M_QGn)^n, n = 1,2, that might be...
Al., J. Albert Et, Ellis, John, Mavromatos, N. E., Nanopoulos, D. V., Sakharov, A. S., Sarkisyan, E. K. G.
We analyze the timing of photons observed by the MAGIC telescope during a flare of the active galactic nucleus Mkn 501 for a possible correlation with energy, as suggested by some models of quantum...
Lahanas, A. B., Mavromatos, N. E., Nanopoulos, D. V.
We show that Supercritical-String-Cosmology (SSC) off-equilibrium and time-dependent-dilaton effects lead to a smoothly evolving dark energy for the last 10 billion years in concordance with all...
Lahanas, A. B., Mavromatos, N. E., Nanopoulos, D. V.
In this work we derive the modifications to the Boltzmann equation governing the cosmic evolution of relic abundances induced by dilaton dissipative-source and non-critical-string terms in...
Ellis, J. R., Mavromatos, N. E., Mitsou, V. A., Nanopoulos, D. V.
We discuss fits of cosmological dark energy models to the available data on high-redshift supernovae. We consider a conventional model with Cold Dark Matter and a cosmological constant (LambdaCDM), a...
Quantum-Gravity Analysis of Gamma-Ray Bursts using Wavelets (2002)
Ellis, J., Mavromatos, N. E., Nanopoulos, D. V., Sakharov, A. S.
In some models of quantum gravity, space-time is thought to have a foamy structure with non-trivial optical properties. We probe the possibility that photons propagating in vacuum may exhibit a...
The Neveu-Schwarz and Ramond Algebras of Logarithmic Superconformal Field Theory (2002)
Mavromatos, N. E., Szabo, R. J.
We describe the general features of the Neveu-Schwarz and Ramond sectors of logarithmic conformal field theories with N=1 supersymmetry. Three particular systems are examined in some detail --...
Astrophysical Probes of the Constancy of the Velocity of Light (1999)
Ellis, J., Farakos, K., Mavromatos, N. E., Mitsou, V., Nanopoulos, D. V.
We discuss possible tests of the constancy of the velocity of light using distant astrophysical sources such as gamma-ray bursters (GRBs), Active Galactic Nuclei (AGNs) and pulsars. This speculative...
A Microscopic Liouville Arrow of Time (1998)
Ellis, John, Mavromatos, N. E., Nanopoulos, D. V.
We discuss the treatment of quantum-gravitational fluctuations in the space-time background as an `environment', using the formalism for open quantum-mechanical systems, which leads to a microscopic...
Hidden Non-Abelian Gauge Symmetries in Doped Planar Antiferromagnets (1996)
Farakos, K., Mavromatos, N. E.
We investigate the possibility of hidden non-Abelian Local Phase symmetries in large-U doped planar Hubbard antiferromagnets, believed to simulate the physics of two-dimensional (magnetic)...
Non-trivial Infrared Structure in (2+1)-dimensional Quantum Electrodynamics (1996)
Aitchison, I. J. R., Amelino-Camelia, G., Klein-Kreisler, M., Mavromatos, N. E., Neill, D. Mc
We show that the gauge-fermion interaction in multiflavour $(2+1)$-dimensional quantum electrodynamics with a finite infrared cut-off is responsible for non-fermi liquid behaviour in the infrared, in...
Quantum Decoherence in a Four-Dimensional Black Hole Background (1996)
John Ellis, N.E. Mavromatos, D. V. Nanopoulos, Elizabeth Winstanley
We display a logarithmic divergence in the density matrix of a scalar field in the presence of an Einstein-Yang-Mills black hole in four dimensions. This divergence is related to a previously-found...
Dilatonic Black Holes in Higher Curvature String Gravity (1995)
Kanti, P., Mavromatos, N. E., Rizos, J., Tamvakis, K., Winstanley, E.
We give analytical arguments and demonstrate numerically the existence of black hole solutions of the $4D$ Effective Superstring Action in the presence of Gauss-Bonnet quadratic curvature terms. The...