Results for "M. Chatzikos"

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H, He-like recombination spectra II: $l$-changing collisions for He Rydberg statesAug 31 2016Cosmological models can be constrained by determining primordial abundances. Accurate predictions of the He I spectrum are needed to determine the primordial helium abundance to a precision of $< 1$% in order to constrain Big Bang Nucleosynthesis models. ... More
H-, He-like recombination spectra III: $n$-changing collisions in highly-excited Rydberg states and their impact on the radio, IR and optical recombination linesMar 13 2019At intermediate to high densities, electron (de-)excitation collisions are the dominant process for populating or depopulating high Rydberg states. In particular, the accurate knowledge of the energy changing ($n$-changing) collisional rates is determinant ... More
H-, He-like recombination spectra III: $n$-changing collisions in highly-excited Rydberg states and their impact on the radio, IR and optical recombination linesMar 13 2019Mar 18 2019At intermediate to high densities, electron (de-)excitation collisions are the dominant process for populating or depopulating high Rydberg states. In particular, the accurate knowledge of the energy changing ($n$-changing) collisional rates is determinant ... More
H, He-like recombination spectra I: $l$-changing collisions for hydrogenApr 13 2016Hydrogen and helium emission lines in nebulae form by radiative recombination. This is a simple process which, in principle, can be described to very high precision. Ratios of He I and H I emission lines can be used to measure the He$^+$/H$^+$ abundance ... More
Suppression of Dielectronic Recombination Due to Finite Density Effects II: Analytical Refinement and Application to Density-dependent Ionization Balances and AGN Broad-line EmissionAug 22 2018We present improved fits to our treatment of suppression of dielectronic recombination at intermediate densities. At low densities, most recombined excited states eventually decay to the ground state, and therefore the total dielectronic recombination ... More
Ultraviolet emission lines of Si II in cool star and solar spectraOct 29 2015Recent atomic physics calculations for Si II are employed within the Cloudy modelling code to analyse Hubble Space Telescope (HST) STIS ultraviolet spectra of three cool stars, Beta-Geminorum, Alpha-Centauri A and B, as well as previously published HST/GHRS ... More
Accurate determination of the free-free Gaunt factor; I - non-relativistic Gaunt factorsJul 18 2014Aug 17 2014Modern spectral synthesis codes need the thermally averaged free-free Gaunt factor defined over a very wide range of parameter space in order to produce an accurate prediction for the spectrum emitted by an ionized plasma. Until now no set of data exists ... More
Stout: Cloudy's Atomic and Molecular DatabaseJun 04 2015We describe a new atomic and molecular database we developed for use in the spectral synthesis code Cloudy. The design of Stout is driven by the data needs of Cloudy, which simulates molecular, atomic, and ionized gas with kinetic temperatures 2.8 K < ... More
Accurate determination of the free-free Gaunt factor. II - relativistic Gaunt factorsFeb 24 2015When modelling an ionised plasma, all spectral synthesis codes need the thermally averaged free-free Gaunt factor defined over a very wide range of parameter space in order to produce an accurate prediction for the spectrum. Until now no data set exists ... More
Implications of Coronal Line Emission in NGC 4696Oct 16 2014We announce a new facility in the spectral code CLOUDY that enables tracking the evolution of a cooling parcel of gas with time. For gas cooling from temperatures relevant to galaxy clusters, earlier calculations estimated the [Fe XIV] {\lambda}5303 / ... More
Chandra Observation of Abell 2065: An Unequal Mass Merger?Feb 08 2006We present an analysis of a 41 ks Chandra observation of the merging cluster Abell 2065 with the ACIS-I detector. Previous observations with ROSAT and ASCA provided evidence for an ongoing merger, but also suggested that there were two surviving cooling ... More
On the Observability of Optically Thin Coronal Hyperfine Structure LinesJun 03 2014We present Cloudy calculations for the intensity of coronal hyperfine lines in various environments. We model indirect collisional and radiative transitions, and quantify the collisionally-excited line emissivity in the density-temperature phase-space. ... More
Deep Chandra, HST-COS, and Megacam Observations of the Phoenix Cluster: Extreme Star Formation and AGN Feedback on Hundred Kiloparsec ScalesAug 24 2015We present new ultraviolet, optical, and X-ray data on the Phoenix galaxy cluster (SPT-CLJ2344-4243). Deep optical imaging reveals previously-undetected filaments of star formation, extending to radii of ~50-100 kpc in multiple directions. Combined UV-optical ... More
Space Telescope and Optical Reverberation Mapping Project. X. Understanding the Absorption-Line Holiday in NGC 5548Dec 30 2018Apr 25 2019The flux variations in the emission lines in active galactic nuclei (AGNs) are driven by variations in the ionizing continuum flux --which are usually reflected in the observable UV-optical continuum. The "Reverberation mapping" technique measures the ... More
Space Telescope and Optical Reverberation Mapping Project. X. The Hidden Life of "the Obscurer" in NGC 5548 and Understanding the Absorption-Line HolidayDec 30 2018Jan 02 2019The flux variations in the emission lines in active galactic nuclei (AGNs) are driven by variations in the ionizing continuum flux --which are usually reflected in the observable UV-optical continuum. The "Reverberation mapping" technique measures the ... More
Effects of External Radiation Fields on Line Emission - Application to Star-forming RegionsOct 29 2013A variety of astronomical environments contain clouds irradiated by a combination of isotropic and beamed radiation fields. For example, molecular clouds may be irradiated by the isotropic cosmic microwave background (CMB), as well as by a nearby active ... More
Challenges and Techniques for Simulating Line EmissionAug 24 2018Modeling emission lines from the millimeter to the UV and producing synthetic spectra is crucial for a good understanding of observations, yet it is an art filled with hazards. This is the proceedings of "Walking the Line", a 3-day conference held in ... More
A new signal for scalar top bound state productionOct 01 1993We study the production and decay of a scalar \stst\ bound state \sigst\ at hadron supercolliders, where \st\ is the lighter stop eigenstate. If \st\ has no tree--level 2--body decays, the dominant decay modes of \sigst\ are $gg$ or, if $m_h < \mst \ll ... More
Massive Neutrino in Non-commutative Space-timeDec 24 2007Apr 01 2008We consider the noncommutative standard model based on $SU(3)\times SU(2)\times U(1)$. We study the gauge transformation of right handed neutrino and its direct interaction with photon in the noncommutative space-time. We show that the massive Dirac neutrinos, ... More
Infinite order excitonic Bloch equations for asymmetric nanostructuresJul 04 2003We present a new exciton-based formalism for calculating the coherent response of asymmetric semiconductor multiple quantum well structures to ultra-short optical pulses valid to infinite order in the optical field and including the self-generated intraband ... More
Scalar StoponiumAug 18 1993We study the decays of a scalar \stst\ bound state \sigst, where \st\ is the lighter stop eigenstate. If \st\ has no tree--level 2--body decays, the dominant decay modes of \sigst\ are $gg$ or, if $m_h < \mst \ll \mstt$, a pair of light scalar Higgs bosons ... More
Photon Neutrino Scattering in Non-Commutative SpaceNov 04 2005Jan 19 2006We extend the non-commutative standard model based on the minimal $SU(3)\times SU(2)\times U(1)$ gauge group to include the interaction of photon with neutrino. We show that, in the gauge invariant manner, only the right handed neutrino can directly couple ... More
Production and Decay of Scalar Stoponium Bound StatesDec 02 1993In this paper we discuss possible signatures for the production of scalar \stst\ (stoponium) bound states \sigst\ at hadron colliders, where \st\ is the lighter scalar top eigenstate. We first study the decay of \sigst; explicit expressions are given ... More
Parton Model in Lorentz Invariant Non-Commutative SpaceMay 26 2004Aug 22 2004We consider the Lorentz invariant non-commutative QED and complete the Feynman rules for the theory up to the order $\theta^2$. In the Lorentz invariant version of the non-commutative QED the particles with fractional charges can be also considered. We ... More
Electromagnetic Response of Weyl SemimetalsMar 22 2013Jun 27 2013It has been suggested recently, based on subtle field-theoretical considerations, that the electromagnetic response of Weyl semimetals and the closely related Weyl insulators can be characterized by an axion term E.B with space and time dependent axion ... More
The Charm Quark Contribution to the Proton Structure FunctionOct 14 2006Dec 27 2006The charm quark structure function $F^c_2$ and the longitudinal structure function $F_l^p$ are directly sensitive to the gluon content of proton and therefore are crucial in understanding of proton structure function, in particular at low momentum transfer ... More
The decay of singlet scalar dark matter to unparticle and photonMay 06 2008We consider the unparticle physics introduced by Georgi and show that if the standard model is extended to include a singlet scalar as a dark matter candidate, there is a channel which leads to its decay to photon and unparticle. We calculate the decay ... More
Lorentz Conserving Noncommutative Standard ModelMar 29 2007May 10 2007We consider Lorentz conserving noncommutative field theory to construct the Lorentz conserving noncommutative standard model based on the gauge group $SU(3)\times SU(2)\times U(1)$. We obtain the enveloping algebra-valued of Higgs field up to the second ... More
Shelving and Probe Efficiency in Trapped Ion ExperimentsFeb 24 2014A generalized probe sequence typical of trapped ion experiments using shelving is studied. Detection efficiency is analyzed for finite shelved state lifetimes and using multi-modal count distributions. Multi-modal distributions are more appropriate for ... More
The Neutralino Relic Density in Minimal N=1 SupergravityJul 10 1992We compute the cosmic relic (dark matter) density of the lightest supersymmetric particle (LSP) in the framework of minimal $N=1$ Supergravity models with radiative breaking of the electroweak gauge symmetry. To this end, we re--calculate the cross sections ... More
Quantization and $2π$ Periodicity of the Axion Action in Topological InsulatorsJun 17 2010Nov 10 2010The Lagrangian describing the bulk electromagnetic response of a three-dimensional strong topological insulator contains a topological `axion' term of the form '\theta E dot B'. It is often stated (without proof) that the corresponding action is quantized ... More
On the effect of the thermal gas component to the stability of vortices in trapped Bose-Einstein condensatesMar 12 2002We study the stability of vortices in trapped single-component Bose-Einstein condensates within self-consistent mean-field theories--especially we consider the Hartree-Fock-Bogoliubov-Popov theory and its recently proposed gapless extensions. It is shown ... More
Phase boundaries of a spin-3/2 Blume-Emery-Griffiths model on a honeycomb latticeOct 11 2013The spin-3/2 Blume-Emery-Griffiths model on a honeycomb lattice is studied by Monte Carlo simulations with the goal to determine phase diagrams for a range of the model parameters and to investigate the nature of the phase transitions between the respective ... More
Flares on A-type stars: Evidence for heating of solar corona by nanoflares?Aug 11 2016We analyzed the occurrence rates of flares on stars of spectral types K, G, F, and A, observed by Kepler. We found that the histogram of occurrence frequencies of stellar flares is systematically shifted towards a high-energy tail for A-type stars compared ... More
The Formation Rates of Population III Stars and Chemical Enrichment of Halos during the Reionization EraJan 06 2009[abridged] The First Stars in the Universe form out of pristine primordial gas clouds that have been radiatively cooled to a few hundreds of degrees Kelvin either via molecular or atomic (Lyman-Alpha) hydrogen lines. This primordial mode of star formation ... More
Symmetry Adaptation Techniques in n-Photon Absorption SpectroscopyOct 27 1998We present some recent progress achieved in the application of symmetry adaptation techniques to n-photon absorption spectroscopy of rare earth ions in finite symmetry. More specifically, this work is concerned with the determination of the intensity ... More
Two-Photon Spectroscopy of Transition-Metal Ions in Cubical SymmetryOct 26 1998Symmetry adaptation techniques are applied to the determination of intensities of intra-configurational two-photon transitions for transition-metal ions in cubical symmetry. This leads to a simple model giving the polarization dependence of intensities ... More
An Alternative Basis for the Wigner-Racah Algebra of the Group SU(2)Dec 17 1997The Lie algebra of the classical group SU(2) is constructed from two quon algebras for which the deformation parameter is a common root of unity. This construction leads to (i) a not very well-known polar decomposition of the ladder generators of the ... More
Enhanced Sampling in the Well-Tempered EnsembleOct 26 2009Apr 13 2010We introduce the well-tempered ensemble (WTE) which is the biased ensemble sampled by well-tempered metadynamics when the energy is used as collective variable. WTE can be designed so as to have approximately the same average energy as the canonical ensemble ... More
Berry's Phase Induced Bose-Einstein condensation into a Vortex StateNov 23 1998The existence of a geometric phase in magnetic traps can be used to Bose condense a magnetically trapped atomic gas into a vortex state. We propose an experimental setup where a magnetic trap together with a blue detuned laser beam form a multiply connected ... More
Superconducting state in Fe-based materials and spin-fluctuation theory of pairingOct 28 2015Short review of the spin-fluctuation theory of superconductive pairing in iron-based pnictides and chalcogenides.
QCD_{1+1} with Static Quarks as Supersymmetric Quantum MechanicsFeb 09 1998We reexamine the solvable model problem of two static, fundamental quarks interacting with a SU(2) Yang-Mills field on a spatial circle, introduced by Engelhardt and Schreiber. If the quarks are at the same point, the model exhibits a quantum mechanical ... More
Massive Binary Black Holes in the Cosmic LandscapeJun 23 2009Binary black holes occupy a special place in our quest for understanding the evolution of galaxies along cosmic history. If massive black holes grow at the center of (pre-)galactic structures that experience a sequence of merger episodes, then dual black ... More
Einstein and the mystery of eternity of lifeApr 08 2009While Special and General Relativity are well known by a very large number of people, Einstein's religious convinctions are almost ignored. The paper focuses on what was his view about immortality. Einstein believed in Spinoza's view of God and in cosmic ... More
Effect of inelastic scattering on parametric pumpingAug 03 2001Pumping of charge in phase-coherent mesoscopic systems due to the out-of-phase modulation of two parameters has recently found considerable interest. We investigate the effect of inelastic processes on the adiabatically pumped current through a two terminal ... More
Hidden quantum pump effects in quantum coherent ringsFeb 27 2003Time periodic perturbations of an electron system on a ring are examined. For small frequencies periodic small amplitude perturbations give rise to side band currents which in leading order are inversely proportional to the frequency. These side band ... More
Dynamic scattering channels of a double barrier structureApr 02 2008We calculate analytically the Floquet scattering matrix for a periodically driven double-barrier structure. Our approach takes into account dynamical effects which become necessarily important when electrons propagate through a system subject to a fast ... More
Dissipation and noise in adiabatic quantum pumpsJan 16 2002We investigate the distribution function, the heat flow and the noise properties of an adiabatic quantum pump for an arbitrary relation of pump frequency $\omega$ and temperature. To achieve this we start with the scattering matrix approach for ac-transport. ... More
Remarks on the high-energy behaviour of cross-sections in weak-scale string theoriesSep 20 2001We consider the high-energy behaviour of processes involving Kaluza-Klein (KK) gravitons of weak-scale string theories. We discuss how form-factors derived within string theory modify the couplings of KK gravitons and thereby lead to an exponential fall-off ... More
Metastability in Two Dimensions and the Effective PotentialApr 12 1993We study analytically and numerically the decay of a metastable phase in (2+1)-dimensional classical scalar field theory coupled to a heat bath, which is equivalent to two-dimensional Euclidean quantum field theory at zero temperature. By a numerical ... More
New analyticity constraints on the high energy behavior of hadron-hadron cross sectionsJan 25 2006Mar 16 2006We here comment on a series of recent papers by Igi and Ishida[K. Igi and M. Ishida, Phys. Lett B 622, 286 (2005)] and Block and Halzen[M. M. Block and F. Halzen, Phys. Rev D 72, 036006 (2005)] that fit high energy $pp$ and $\bar pp$ cross section and ... More
Factorization Theorems for High Energy nn, gamma p and gamma gamma ScatteringFeb 17 2003The robustness of the factorization theorem for total cross sections, $\sigma_{nn}/\sigma_{\gamma p}=\sigma_{\gamma p}/\sigma_{\gamma\gamma}$, originally proved by Block and Kaidalov\cite{bk} for $nn$ (the even portion of $pp$ and $\pbar p$ scattering), ... More
Visualising a FuseOct 27 2010Nov 09 2010In this brief article I describe an experiment to illustrate how a fuse works. I have used this as part of lessons for my year 11 classes to demonstrate how an electrical fuse 'blows' when too high a current passes through it.
General models of Einstein gravity with a non-Newtonian weak-field limitJan 08 2009We investigate Einstein theories of gravity, coupled to a scalar field \vphi and point-like matter, which are characterized by a scalar field-dependent matter coupling function e^{H(\vphi)}. We show that under mild constraints on the form of the potential ... More
Two Loop Electroweak Bosonic Corrections to the Muon Decay LifetimeNov 04 2002Nov 19 2002A review of the calculation of the two loop bosonic corrections to $\Delta r$ is presented. Factorization and matching onto the Fermi model are discussed. An approximate formula, describing the quantity over the interesting range of Higgs boson mass values ... More
Structure and stability of Al$_2$FeJul 01 2011We employ first principles total energy and phonon calculations to address the structure and stability of Al$_2$Fe. This structure, which is reported as stable in the assessed Al-Fe phase diagram, is distinguished by an unusually low triclinic symmetry. ... More
Stability of Fe-based alloys with structure type C6Cr23Jul 23 2004Bulk metallic glass forms when liquid metal alloys solidify without crystalization. In the search for Iron-based bulk glass-forming alloys of the metal-metalloid type (Fe-B- and Fe-C-based), crystals based on the structural prototype C6Cr23 often preempt ... More
Cohesive energies of Fe-based glass-forming alloysMay 13 2004We calculate the cohesive energies of Fe-based glass-forming alloys in the B-Fe-Y-Zr quaternary system. Our {\it ab-initio} calculations fully relax atomic positions and lattice parameters yielding enthalpies of mixing at T=0K. We examine both the known ... More
Efficiently Extracting Energy from Cosmological NeutrinosJul 02 2013Aug 20 2013Detecting the extremely low-energy neutrinos that form the Cosmic Neutrino Background (CNB) presents many experimental challenges, but pursuing this elusive goal is still worthwhile because these weakly-interacting particles could provide a new window ... More
Are the sungrazing comets the inner source of pickup ions and energetic neutral atoms?May 07 2004Feb 11 2005We present arguments that at least part of the inner source of pickup ions in the solar wind might be the material released by sungrazing comets. Based on a statistical analysis of sungrazing comets detected over almost eight years of LASCO operation ... More
Beyond the Kolmogorov Johnson Mehl Avrami kinetics: inclusion of the spatial correlationApr 16 2003The Kolmogorov-Johnson-Mehl-Avrami model, which is a nucleation and growth poissonian process in space, has been implemented by taking into account spatial correlation among nuclei. This is achieved through a detailed study of a system of distinguishable ... More
On the stability operator for MOTS and the 'core' of Black HolesOct 13 2012Small deformations of marginally (outer) trapped surfaces are considered by using their stability operator. In the case of spherical symmetry, one can use these deformations on any marginally trapped round sphere to prove several interesting results. ... More
On the boundary of the region containing trapped surfacesDec 15 2008The boundary of the region in spacetime containing future-trapped closed surfaces is considered. In asymptotically flat spacetimes, this boundary does not need to be the event horizon nor a dynamical/trapping horizon. Some properties of this boundary ... More
The universal 'energy' operatorAug 12 2006Oct 05 2006The "positive square" of any tensor is presented in a universal and unified manner, valid in Lorentzian manifolds of arbitrary dimension, and independently of any (anti)-symmetry properties of the tensor. For rank-m tensors, the positive square has rank ... More
Trapped surfaces, horizons and exact solutions in higher dimensionsMar 30 2002May 18 2002A very simple criterion to ascertain if (D-2)-surfaces are trapped in arbitrary D-dimensional Lorentzian manifolds is given. The result is purely geometric, independent of the particular gravitational theory, of any field equations or of any other conditions. ... More
Applications of Super-Energy TensorsDec 13 1999In this contribution I intend to give a summary of the new relevant results obtained by using the general superenergy tensors. After a quick review of the definition and properties of these tensors, several of their mathematical and physical applications ... More
A New Type of Singularity TheoremDec 10 2007A new type of singularity theorem, based on spatial averages of physical quantities, is presented and discussed. Alternatively, the results inform us of when a spacetime can be singularity-free. This theorem provides a decisive observational difference ... More
Weyl Semimetal from the Honeycomb Array of Topological Insulator NanowiresNov 15 2012We show that isolated Weyl nodes can arise in a system of parallel topological insulator nano-wires arranged in a honeycomb fashion. This introduces another theoretical example of a topological semi-metal phase with more than one pair of Weyl nodes and ... More
Spin fluctuations of non-equilibrium electrons and excitons in semiconductorsNov 24 2015Effects related with deviations from thermodynamic equilibrium take a special place in the modern physics. Among those, non-equilibrium phenomena in quantum systems attract the highest interest. To date, the experimental technique of spin noise spectroscopy ... More
Spin noise of localized electrons: Interplay of hopping and hyperfine interactionMar 27 2015Apr 17 2015The theory of spin fluctuations is developed for an ensemble of localized electrons taking into account both hyperfine interaction of electron and nuclear spins and electron hopping between the sites. The analytical expression for the spin noise spectrum ... More
Effect of structure anisotropy on low temperature spin dynamics in quantum wellsFeb 07 2007Spin dynamics of two-dimensional electron gas confined in an asymmetrical quantum well is studied theoretically in the regime where the scattering frequency is comparable with the spin precession frequency due to the conduction band spin splitting. The ... More
Normal modes for metric fluctuations in a class of higher-dimensional backgroundsApr 01 1996Jan 13 1997We discuss a gauge invariant approach to the theory of cosmological perturbations in a higher-dimensonal background. We find the normal modes which diagonalize the perturbed action, for a scalar field minimally coupled to gravity, in a higher-dimensional ... More
Quantum Squeezing and Cosmological Entropy ProductionJul 20 1993The entropy growth in a cosmological process of pair production is completely determined by the associated squeezing parameter, and is insensitive to the number of particles in the initial state. The total produced entropy may represent a significant ... More
Entropy Production in the Cosmological Amplification of the Vacuum FluctuationsJan 12 1993We estimate the entropy associated to a background of squeezed cosmic gravitons, and we argue that the process of cosmological pair production from the vacuum may explain the large amount of entropy of our present universe.
ON THE LOW-TEMPERATURE ORDERING OF THE 3D ATIFERROMAGNETIC THREE-STATE POTTS MODELApr 24 1995The antiferromagnetic three-state Potts model on the simple-cubic lattice is studied using Monte Carlo simulations. The ordering in a medium temperature range below the critical point is investigated in detail. Two different regimes have been observed: ... More
CRITICAL EXPONENTS OF THE 3D ANTIFERROMAGNETIC THREE-STATE POTTS MODEL USING THE COHERENT-ANOMALY METHODFeb 22 1995Feb 25 1995The antiferromagnetic three-state Potts model on the simple-cubic lattice is studied using the coherent-anomaly method (CAM). The CAM analysis provides the estimates for the critical exponents which indicate the XY universality class, namely $\alpha=-0.011 ... More
Modelling sublimation and atomic layer epitaxy in the presence of competing surface reconstructionsOct 09 2000Dec 01 2000We present a solid-on-solid model of a binary AB compound, where atoms of type A in the topmost layer interact via anisotropic interactions different from those inside the bulk. Depending on temperature and particle flux, this model displays surface reconstructions ... More
Quantum Estimation by Local ObservablesJan 30 2004Jul 20 2004Quantum estimation theory provides optimal observations for various estimation problems for unknown parameters in the state of the system under investigation. However, the theory has been developed under the assumption that every observable is available ... More
Impossibility of distant indirect measurement of the quantum Zeno effectOct 14 2003Aug 03 2004We critically study the possibility of quantum Zeno effect for indirect measurements. If the detector is prepared to detect the emitted signal from the core system, and the detector does not reflect the signal back to the core system, then we can prove ... More
The interplay between radio galaxies and cluster environmentMay 04 2007By combining the REFLEX and NORAS cluster datasets with the NVSS radio catalogue, we obtain a sample of 145, z<0.3, X-ray selected clusters brighter than 3 10^(-12) erg/s/cm^2 that show a central radio emission above 3 mJy. For virial masses M_vir<~10^(14.5) ... More
Effects of the $U_A(1)$ Anomaly on $η\to 2 γ$ DecayJun 07 1995We study the $\eta \to 2 \gamma$ decay using an extended three-flavor Nambu-Jona-Lasinio model that includes the 't~Hooft instanton induced interaction. The $\eta$ meson mass and the $\eta \to 2 \gamma$ decay width are reproduced simultaneously with a ... More
Microscopic entropy of the most general four-dimensional BPS black holeAug 25 2000Sep 18 2000In a recent paper we have given the macroscopic and microscopic description of the generating solution of toroidally compactified string theory BPS black holes. In this note we compute its corresponding microscopic entropy. Since by definition the generating ... More
Precision tests via radiative $μ$ and $τ$ leptonic decaysFeb 01 2016The branching fractions of radiative leptonic $\tau$ decays $(\tau \to l \nu \bar{\nu} \gamma$, $l=e,\mu)$ were recently measured by the Babar collaboration with a relative error of about 3%. The measurement of the branching ratio $\mathcal{B} (\tau \to ... More
Metallicity Dependence of the Cepheid CalibrationJul 21 1997We point out that the absolute magnitude of the Galactic Cepheids, which have been used for local calibrations for Cepheid period-luminosity relation, shows an unexpectedly large metal abundance effect. This indicates that either Cepheids period luminosity ... More
Primordial Magnetic Fields, Right Electrons, and the Abelian AnomalyFeb 28 1997Jul 17 1997In the standard model there are charges with abelian anomaly only (e.g. right-handed electron number) which are effectively conserved in the early universe until some time shortly before the electroweak scale. A state at finite chemical potential of such ... More
Boundary Conditions, Energies and Gravitational Heat in General Relativity (a Classical Analysis)Feb 18 2004May 25 2004The variation of the energy for a gravitational system is directly defined from the Hamiltonian field equations of General Relativity. When the variation of the energy is written in a covariant form it splits into two (covariant) contributions: one of ... More
II. Non-commuting Matrix Solution of DGLAP; $F_2 {p,d}$ Data Leading to Partons Directly without ParameterizationAug 24 2011Sep 11 2013Dominant present path for determination of quarks and gluon distribution functions from data is based on pre-assumed form of parameters. Here, an alternative direct, or non-parametric method is spelled out. As the main task, least square estimates of ... More
Diophantine approximation, Khintchine's theorem, torus geometry and Hausdorff dimensionOct 23 2007A general form of the Borel-Cantelli Lemma and its connection with the proof of Khintchine's Theorem on Diophantine approximation and the more general Khintchine-Groshev theorem are discussed. The torus geometry in the planar case allows a relatively ... More
Lepton Flavour Mixing Matrix and CP Violation from Neutrino Oscillation ExperimentsJul 09 2001The measurement of the charged-current 8B solar neutrino reaction on deuterium at the Sudbury Neutrino Observatory confirms the neutrino oscillation hypothesis for the solar neutrino problem, and the result favours the solution with large neutrino mixing ... More
AX-GADGET: a new code for cosmological simulations of Fuzzy Dark Matter and Axion modelsJan 24 2018We present a new module of the parallel N-Body code P-GADGET3 for cosmological simulations of light bosonic non-thermal dark matter, often referred as Fuzzy Dark Matter (FDM). The dynamics of the FDM features a highly non-linear Quantum Potential (QP) ... More
Recursion operator for the IGSG equationMay 05 2006In this paper we find the inverse and direct recursion operator for the intrinsic generalized sine-Gordon equation in any number $n > 2$ of independent variables. Among the flows generated by the direct operator we identify a higher-dimensional analogue ... More
Energy Conditions in $f(R,T,R_{μν}T^{μν})$ GravityJun 13 2013Jun 24 2013We discuss the validity of the energy conditions in a newly modified theory named as $f(R,T,R_{\mu\nu}T^{\mu\nu})$ gravity, where $R$ and $T$ represent the scalar curvature and trace of the energy-momentum tensor. The corresponding energy conditions are ... More
Effects of Electromagnetic Field on the Dynamical Instability of Cylindrical CollapseMar 16 2012The objective of this paper is to discuss the dynamical instability in the context of Newtonian and post Newtonian regimes. For this purpose, we consider non-viscous heat conducting charged isotropic fluid as a collapsing matter with cylindrical symmetry. ... More
Two-loop dimensional reduction and effective potential without temperature expansionsMar 13 2000May 23 2000In many extensions of the Standard Model, finite temperature computations are complicated by a hierarchy of zero temperature mass scales, in addition to the usual thermal mass scales. We extend the standard thermal resummations to such a situation, and ... More
Non-commutative and commutative integrability of generic Toda flows in simple Lie algebrasApr 17 1997In this paper we prove the complete integrability of Toda flows on generic coadjoint orbits in simple Lie algebras.
Towards the Scale Invariant CosmologyNov 29 2005An argument is made to show that the singularity in the General Theory of Relativity (GTR) is the expression of a non-Machian feature. It can be avoided with a scale-invariant dynamical theory, a property lacking in GTR. It is further argued that the ... More
Fundamental groups of some special quadric arrangementsJan 18 2006May 29 2007In this work we obtain presentations of fundamental groups of the complements of three families of quadric arrangements in $\mathbb{P}^2$. The first arrangement is a union of $n$ quadrics, which are tangent to each other at two common points. The second ... More
The breathing-mode giant monopole resonance and the surface compressibility in the relativistic mean-field theoryNov 17 2008The breathing-mode isoscalar giant monopole resonance (GMR) is investigated using the generator coordinate method within the relativistic mean-field (RMF) theory. Employing the Lagrangian models of the nonlinear-$\sigma$ model (NL$\sigma$), the scalar-vector ... More
Scalar-vector Lagrangian without nonlinear self-interactions of bosonic fields in the relativistic mean-field theoryMay 05 2008Jul 03 2008A new Lagrangian model without nonlinear scalar self-interactions in the relativistic mean-field (RMF) theory is proposed. Introducing terms for scalar-vector interactions (SVI), we have developed a RMF Lagrangian model for finite nuclei and nuclear matter. ... More
Compressibility of Nuclear Matter from Shell Effects in NucleiApr 13 1999The compressibility of nuclear matter has received significant attention in the last decade and a variety of approaches have been employed to extract this fundamental property of matter. Recently, significant differences have emerged between the results ... More