Nick E. Mavromatos
A5081969425- Cosmology and Gravitation Theories
- Black Holes and Theoretical Physics
- Noncommutative and Quantum Gravity Theories
- Particle physics theoretical and experimental studies
- Dark Matter and Cosmic Phenomena
- Neutrino Physics Research
- Physics of Superconductivity and Magnetism
- Quantum Chromodynamics and Particle Interactions
- Astrophysics and Cosmic Phenomena
- Galaxies: Formation, Evolution, Phenomena
- Computational Physics and Python Applications
- Quantum Mechanics and Applications
- Cold Atom Physics and Bose-Einstein Condensates
- Quantum and electron transport phenomena
- Relativity and Gravitational Theory
- High-Energy Particle Collisions Research
- Biofield Effects and Biophysics
- Quantum, superfluid, helium dynamics
- Pulsars and Gravitational Waves Research
- Quantum Electrodynamics and Casimir Effect
- Quantum Mechanics and Non-Hermitian Physics
- Advanced Differential Geometry Research
- Quantum many-body systems
- Gamma-ray bursts and supernovae
- Atomic and Subatomic Physics Research
National Technical University of Athens
1999-2025
King's College London
2016-2025
University of London
2003-2023
University College London
2003-2023
Physical Sciences (United States)
2023
King's College Hospital
2001-2022
The King's College
2001-2022
Universitat de València
2003-2019
King's College - North Carolina
1999-2018
European Organization for Nuclear Research
2001-2017
We give analytical arguments and demonstrate numerically the existence of black hole solutions 4D effective superstring action in presence Gauss-Bonnet quadratic curvature terms. The possess nontrivial dilaton hair. hair, however, is "secondary type," sense that charge expressed terms mass. Our are not covered by assumptions existing proofs "no-hair" theorem. also find some alternative with singular metric behavior, but finite energy. absence naked singularities this system pointed out.
We present a comprehensive review of keV-scale sterile neutrino Dark Matter, collecting views and insights from all disciplines involved - cosmology, astrophysics, nuclear, particle physics in each case viewed both theoretical experimental/observational perspectives. After reviewing the role active neutrinos physics, we focus on context Matter puzzle. Here, first motivation for based challenges tensions purely cold scenarios. then round out discussion by critically summarizing known...
In this work, we elaborate further on a (3+1)-dimensional cosmological Running-Vacuum-type-Model (RVM) of inflation based string-inspired Chern-Simons(CS) gravity, involving axions coupled to gravitational-CS(gCS) anomalous terms. Inflation in such models is caused by primordial-gravitational-waves(GW)-induced condensation the gCS terms, which leads linear-axion potential. We demonstrate that inflationary phase may be metastable, due existence imaginary parts condensate. These are quantum...
Abstract The unification of quantum mechanics and general relativity has long been elusive. Only recently have empirical predictions various possible theories gravity put to test, where a clear signal properties is still missing. dawn multi-messenger high-energy astrophysics tremendously beneficial, as it allows us study particles with much higher energies travelling longer distances than in terrestrial experiments, but more progress needed on several fronts. A thorough appraisal current...
The recent measurement by ATLAS of light-by-light scattering in LHC Pb-Pb collisions is the first direct evidence for this basic process. We find that it excludes a range mass scale nonlinear Born-Infeld extension QED ≲100 GeV, much stronger constraint than those derived previously. In case standard model which U(1)_{Y} hypercharge gauge symmetry realized nonlinearly, limit on corresponding reach ∼90 which, turn, imposes lower ≳11 TeV magnetic monopole such theory.
The frequency-dependent time delays in fast radio bursts (FRBs) can be used to constrain the photon mass, if FRB redshifts are known, but similarity between frequency dependences of dispersion due plasma effects and a mass complicates derivation limit on $m_\gamma$. measure (DM) 150418 is known $\sim 0.1$%, there claim have measured its redshift with an accuracy 2$%, strength constraint $m_\gamma$ limited by uncertainties modelling host galaxy Milky Way, as well possible inhomogeneities...
We present a model for the Universe in which quantum anomalies are argued to play an important dual role: they responsible generating matter-antimatter asymmetry cosmos, but also provide time-dependent contributions vacuum energy density of ``running-vacuum'' type, drive Universe's evolution. According this scenario, during inflationary phase string-inspired Universe, and its subsequent exit, existence primordial gravitational waves induces anomalies, couple [Kalb-Ramond (KR)] axion field...
In previous works we have derived a Running Vacuum Model (RVM) for string Universe, which provides an effective description of the evolution 4-dimensional string-inspired cosmologies from inflation till present epoch. context this "stringy RVM" version, it is assumed that early Universe characterised by purely gravitational degrees freedom, massless multiplet, including antisymmetric tensor field. The latter plays important role, since its dual gives rise to `stiff' gravitational-axion...
We use Big Bang Nucleosynthesis (BBN) data in order to impose constraints on higher-order modified gravity, and particular on: (i) $f(G)$ Gauss-Bonnet $f(P)$ cubic gravities, arising respectively through the of quadratic-curvature $G$ term, cubic-curvature combination, (ii) string-inspired quadratic gravity coupled dilaton field, (iii) models with quartic curvature corrections, (iv) running vacuum models. perform a detailed investigation BBN epoch we calculate deviations freeze-out...
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 refractive index, by analyzing times flight radiation from gamma-ray bursters (GRBs) known redshifts. use wavelet shrinkage procedure for noise removal and “zoom” technique define high accuracy timings sharp transitions GRB light curves, thereby optimizing sensitivity experimental probes any energy...
We discuss possible tests of the constancy velocity light using distant astrophysical sources such as gamma-ray bursters (GRBs), active galactic nuclei (AGNs), and pulsars. This speculative quest may be motivated by some models quantum fluctuations in spacetime background, we explicitly how an energy-dependent variation photon δc/c ~ -E/M arises one particular quantum-gravitational model. then data on GRBs used to set limits variations light, which illustrate BATSE OSSE observations that...
We present a systematic phenomenological analysis of the tests CPT symmetry that are possible within an open quantum-mechanical description neutral kaon system is motivated by arguments based on quantum gravity and string theory. develop perturbative expansion in terms three small CPT-violating parameters admitted this description, provide expressions for complete set K\ensuremath{\rightarrow}2\ensuremath{\pi}, 3\ensuremath{\pi}, \ensuremath{\pi}l\ensuremath{\nu} decay observables to second...
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 fluctuations. The sensitivity recent astrophysical observations, particularly AGN Mk501 MAGIC Collaboration, approaches Planck scale for depending linearly on photon energy. We present here new derivation this vacuum refraction index, based stringy analogue interaction with internal degrees freedom...
The MoEDAL experiment at Point 8 of the LHC ring is seventh and newest experiment. It dedicated to search for highly-ionizing particle avatars physics beyond Standard Model, extending significantly discovery horizon LHC. A would have revolutionary implications our fundamental understanding Microcosm. an unconventional largely passive detector comprised largest array Nuclear Track Detector stacks ever deployed accelerator, surrounding intersection region on ring. Another novel feature use...
MoEDAL is designed to identify new physics in the form of long-lived highly ionizing particles produced high-energy LHC collisions. Its arrays plastic nuclear-track detectors and aluminium trapping volumes provide two independent passive detection techniques. We present here results a first search for magnetic monopole production 13 TeV proton-proton collisions using technique, extending previous publication with 8 data during Run 1. A total 222 kg detector samples was exposed forward region...
The MoEDAL experiment is designed to search for magnetic monopoles and other highly-ionising particles produced in high-energy collisions at the LHC. largely passive detector, deployed Interaction Point 8 on LHC ring, relies two dedicated direct detection techniques. first technique based stacks of nucleartrack detectors with surface area ~18m2, sensitive particle ionisation exceeding a high threshold. These are analysed offline by optical scanning microscopes. second trapping charged an...