Results for "Y. Akrami"

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An Inhomogeneous Model Universe Behaving HomogeneouslyFeb 10 2007Jun 09 2008We present a new model universe based on the junction of FRW to flat Lemaitre-Tolman-Bondi (LTB) solutions of Einstein equations along our past light cone, bringing structures within the FRW models. The model is assumed globally to be homogeneous, i.e. ... More
Supersymmetry vis-à-vis Observation: Dark Matter Constraints, Global Fits and Statistical IssuesNov 03 2011Weak-scale supersymmetry is one of the most favoured theories beyond the Standard Model of particle physics that elegantly solves various theoretical and observational problems in both particle physics and cosmology. In this thesis, I describe the theoretical ... More
Power asymmetry in WMAP and Planck temperature sky maps as measured by a local variance estimatorFeb 04 2014Mar 24 2014We revisit the question of hemispherical power asymmetry in the WMAP and Planck temperature sky maps by measuring the local variance over the sky and on disks of various sizes. For the 2013 Planck sky map we find that none of the 1000 available isotropic ... More
On the Eigenvalues of the Operator $(Tf)(t)=f(t)-\sum_{n=0}^\infty\frac{f^{(n)}(0)}{n!}t^n$May 13 2011Jun 05 2011We show that the only eigenvalues of this operator are 0 and 1.
On the Series $\sum_{n=0}^\infty t^nf^{(n)}(t) (-1)^n/n!$May 13 2011Jun 05 2011We study the series $\sum_{n=0}^{\infty}\frac{(-1)^n}{n!}t^nf^{(n)}(t)$. We show that for analytic functions this series is uniformly and absolutely convergent to the constant $f(0)$. We show that there are nowhere analytic functions for them the series ... More
Braided Cyclic Cocycles and Non-Associative GeometryJun 01 2004We use monoidal category methods to study the noncommutative geometry of nonassociative algebras obtained by a Drinfeld-type cochain twist. These are the so-called quasialgebras and include the octonions as braided-commutative but nonassociative coordinate ... More
Primordial black holes do not (yet) constrain the primordial power spectrumNov 30 2016Primordial black holes (PBHs) are thought to have formed from extremely overdense regions that reentered the horizon after the end of inflation if there was sufficient power in primordial perturbations on specific scales. The existence (and abundance) ... More
Ratio-Balanced Maximum FlowsFeb 28 2019When a loan is approved for a person or company, the bank is subject to \emph{credit risk}; the risk that the lender defaults. To mitigate this risk, a bank will require some form of \emph{security}, which will be collected if the lender defaults. Accounts ... More
A new effective weighted modified perturbation technique for solving a class of hypersingular integral equationsMay 31 2017This paper is an attempt to solve an important class of hypersingular integral equations of the second kind. To this end, we apply a new weighted and modified perturbation method which includes some special cases of the Adomian decomposition method. To ... More
Constraints on small-scale cosmological perturbations from gamma-ray searches for dark matterMay 07 2012Events like inflation or phase transitions can produce large density perturbations on very small scales in the early Universe. Probes of small scales are therefore useful for e.g. discriminating between inflationary models. Until recently, the only such ... More
Accelerated expansion from ghost-free bigravity: a statistical analysis with improved generalitySep 03 2012Mar 20 2013We study the background cosmology of the ghost-free, bimetric theory of gravity. We perform an extensive statistical analysis of the model using both frequentist and Bayesian frameworks and employ the constraints on the expansion history of the Universe ... More
Uncertainties in primordial black-hole constraints on the primordial power spectrumNov 30 2016Feb 02 2018The existence (and abundance) of primordial black holes (PBHs) is governed by the power spectrum of primordial perturbations generated during inflation. So far no PBHs have been observed, and instead, increasingly stringent bounds on their existence at ... More
Cosmological constraints on ghost-free bigravity: background dynamics and late-time accelerationFeb 21 2013The recent discovery of a ghost-free, non-linear extension of the Fierz-Pauli theory of massive gravity, and its bigravity formulation, introduced new possibilities of interpreting cosmological observations, in particular, the apparent late-time accelerated ... More
Improved constraints on the primordial power spectrum at small scales from ultracompact minihalosOct 11 2011Feb 17 2013For a Gaussian spectrum of primordial density fluctuations, ultracompact minihalos (UCMHs) of dark matter are expected to be produced in much greater abundance than, e.g., primordial black holes. Forming shortly after matter-radiation equality, these ... More
Massive mimetic cosmologyFeb 21 2019We study the first cosmological implications of the mimetic theory of massive gravity recently proposed by Chamseddine and Mukhanov. This is a novel theory of ghost-free massive gravity which additionally contains a mimetic dark matter component. In an ... More
Consistent metric combinations in cosmology of massive bigravityFeb 13 2015Nov 07 2015Massive bigravity models are interesting alternatives to standard cosmology. In most cases, however, these models have been studied for a simplified scenario in which both metrics take homogeneous and isotropic forms [Friedmann-Lema\^itre-Robertson-Walker ... More
How well will ton-scale dark matter direct detection experiments constrain minimal supersymmetry?Nov 18 2010Apr 18 2011Weakly interacting massive particles (WIMPs) are amongst the most interesting dark matter (DM) candidates. Many DM candidates naturally arise in theories beyond the standard model (SM) of particle physics, like weak-scale supersymmetry (SUSY). Experiments ... More
Statistical coverage for supersymmetric parameter estimation: a case study with direct detection of dark matterNov 18 2010Jul 13 2011Models of weak-scale supersymmetry offer viable dark matter (DM) candidates. Their parameter spaces are however rather large and complex, such that pinning down the actual parameter values from experimental data can depend strongly on the employed statistical ... More
A spectre is haunting the cosmos: Quantum stability of massive gravity with ghostsMay 27 2016Nov 29 2016Many theories of modified gravity with higher order derivatives are usually ignored because of serious problems that appear due to an additional ghost degree of freedom. Most dangerously, it causes an immediate decay of the vacuum. However, breaking Lorentz ... More
The landscape, the swampland and the era of precision cosmologyAug 28 2018Oct 12 2018We review the advanced version of the KKLT construction and pure $d=4$ de Sitter supergravity, involving a nilpotent multiplet, with regard to various conjectures that de Sitter state cannot exist in string theory. We explain why we consider these conjectures ... More
On nonlocally interacting metrics, and a simple proposal for cosmic accelerationFeb 28 2017Mar 20 2018We propose a simple, nonlocal modification to general relativity (GR) on large scales, which provides a model of late-time cosmic acceleration in the absence of the cosmological constant and with the same number of free parameters as in standard cosmology. ... More
A spectre is haunting the cosmos: Quantum stability of massive gravity with ghostsMay 27 2016Jun 06 2016Many theories of modified gravity with higher order derivatives are usually ignored because of serious problems that appear due to an additional ghost degree of freedom. Most dangerously, it causes an immediate decay of the vacuum. However, breaking Lorentz ... More
Monitoring Targeted Hate in Online EnvironmentsMar 13 2018Hateful comments, swearwords and sometimes even death threats are becoming a reality for many people today in online environments. This is especially true for journalists, politicians, artists, and other public figures. This paper describes how hate directed ... More
Linear growth of structure in massive bigravityApr 15 2014Oct 02 2014The ghost-free theory of massive gravity with two dynamical metrics has been shown to produce viable cosmological expansion, where the late-time acceleration of the Universe is due to the finite range of the gravitational interaction rather than a nonzero ... More
The nature of spacetime in bigravity: two metrics or none?Mar 31 2014Aug 13 2014The possibility of matter coupling to two metrics at once is considered. This appears natural in the most general ghost-free, bimetric theory of gravity, where it unlocks an additional symmetry with respect to the exchange of the metrics. This double ... More
A spectre is haunting the cosmos: Quantum stability of massive gravity with ghostsMay 27 2016Oct 21 2016Many theories of modified gravity with higher order derivatives are usually ignored because of serious problems that appear due to an additional ghost degree of freedom. Most dangerously, it causes an immediate decay of the vacuum. However, breaking Lorentz ... More
A Profile Likelihood Analysis of the Constrained MSSM with Genetic AlgorithmsOct 21 2009Mar 23 2010The Constrained Minimal Supersymmetric Standard Model (CMSSM) is one of the simplest and most widely-studied supersymmetric extensions to the standard model of particle physics. Nevertheless, current data do not sufficiently constrain the model parameters ... More
Dark energy, $α$-attractors, and large-scale structure surveysDec 27 2017May 31 2018Over the last few years, a large family of cosmological attractor models has been discovered, which can successfully match the latest inflation-related observational data. Many of these models can also describe a small cosmological constant $\Lambda$, ... More
Neutron star merger GW170817 strongly constrains doubly coupled bigravityMar 26 2018Jun 14 2018We study the implications of the recent detection of gravitational waves emitted by a pair of merging neutron stars and their electromagnetic counterpart, events GW170817 and GRB170817A, on the viability of the doubly coupled bimetric models of cosmic ... More
Cosmic expansion histories in massive bigravity with symmetric matter couplingSep 09 2014Jan 10 2015We study the cosmic expansion history of massive bigravity with a viable matter coupling which treats both metrics on equal footing. We derive the Friedmann equation for the effective metric through which matter couples to the two metrics, and study its ... More
Aller guten Dinge sind drei: Cosmology with three interacting spin-2 fieldsApr 14 2016Sep 01 2016Theories of massive gravity with one or two dynamical metrics generically lack stable and observationally-viable cosmological solutions that are distinguishable from $\Lambda$CDM. We consider an extension to trimetric gravity, with three interacting spin-2 ... More
Bimetric gravity doubly coupled to matter: theory and cosmological implicationsMay 31 2013Oct 24 2013A ghost-free theory of gravity with two dynamical metrics both coupled to matter is shown to be consistent and viable. Its cosmological implications are studied, and the models, in particular in the context of partially massless gravity, are found to ... More
Integrated Sachs-Wolfe effect in massive bigravityJan 09 2015Apr 21 2015We study the integrated Sachs-Wolfe (ISW) effect in ghost-free, massive bigravity. We focus on the infinite-branch bigravity (IBB) model which exhibits viable cosmic expansion histories and stable linear perturbations, while the cosmological constant ... More
Dynamical analysis of $R\dfrac{1}{\Box^{2}}R$ cosmology: Impact of initial conditions and constraints from supernovaeJun 02 2016Aug 30 2016We discuss the cosmological implications of the $R~\Box^{-2}R$ nonlocal modification to standard gravity. We relax the assumption of special initial conditions in the local formulation of the theory, perform a full phase-space analysis of the system, ... More
Bimetric gravity is cosmologically viableMar 25 2015Jul 04 2015Bimetric theory describes gravitational interactions in the presence of an extra spin-2 field. Previous work has suggested that its cosmological solutions are generically plagued by instabilities. We show that by taking the Planck mass for the second ... More
On instabilities in tensorial nonlocal gravityOct 06 2016We discuss the cosmological implications of nonlocal modifications of general relativity containing tensorial structures. Assuming the presence of standard radiation- and matter-dominated eras, we show that, except in very particular cases, the nonlocal ... More
Inflationary power asymmetry from primordial domain wallsAug 13 2014Nov 29 2014We study the asymmetric primordial fluctuations in a model of inflation in which translational invariance is broken by a domain wall. We calculate the corrections to the power spectrum of curvature perturbations; they are anisotropic and contain dipole, ... More
Instabilities in tensorial nonlocal gravityOct 06 2016Feb 26 2017We discuss the cosmological implications of nonlocal modifications of general relativity containing tensorial structures. Assuming the presence of standard radiation- and matter-dominated eras, we show that, except in very particular cases, the nonlocal ... More
Decay Constants $f_{D_s^*}$ and $f_{D_s}$ from ${\bar{B}}^0\to D^+ l^- {\barν}$ and ${\bar{B}}^0\to D^+ D_s^{-(*)}$ DecaysOct 15 1998Oct 22 1998We calculate the decay constant of $D_s$ and $D_s^{*}$ with $\bar{B}^0 \ra D^{+}\ell^{-}\nu$ and $\bar{B}^0 \ra D^{+}D_s^{-(*)}$ decays. In our analysis we assume that factorization ansatz works and used two different form factor behaviours (constant ... More
Backwards on Minkowski's road. From 4D to 3D Maxwellian electromagnetismJul 16 2008Minkowski's concept of a four-dimensional physical space is a central paradigm of modern physics. The three-dimensional Maxwellian electrodynamics is uniquely generalized to the covariant four-dimensional form. Is the (1+3) decomposition of the covariant ... More
Local Procrustes for Manifold Embedding: A Measure of Embedding Quality and Embedding AlgorithmsJun 16 2008We present the Procrustes measure, a novel measure based on Procrustes rotation that enables quantitative comparison of the output of manifold-based embedding algorithms (such as LLE (Roweis and Saul, 2000) and Isomap (Tenenbaum et al, 2000)). The measure ... More
VLBI Surveys of Active Galactic NucleiApr 07 2008A review is given on the current status and selected results from large VLBI surveys of compact extragalactic radio sources made between 13 cm and 3 mm wavelengths and covering the entire sky. More than 4200 objects are observed and imaged with dynamic ... More
Space-time Geometry in Exactly Solvable Quantum Dilaton GravityOct 23 1993Nov 04 1993We describe in detail how one can extract space-time geometry in an exactly solvable model of quantum dilaton gravity of the type proposed by Callan, Giddings, Harvey and Strominger ( CGHS ). Based on our previous work, in which a model with 24 massless ... More
Extraction of Black Hole Geometry in Exactly Quantized Two Dimensional Dilaton GravityOct 23 1993Based on our previous work, in which a model of two dimensional dilaton gravity of the type proposed by Callan, Giddings, Harvey and Strominger was rigorously quantized, we explicitly demonstrate how one can extract space-time geometry in exactly solvable ... More
Free-Energy Calculations in Protein Folding by Generalized-Ensemble AlgorithmsFeb 16 2001We review uses of the generalized-ensemble algorithms for free-energy calculations in protein folding. Two of the well-known methods are multicanonical algorithm and replica-exchange method; the latter is also referred to as parallel tempering. We present ... More
Neutrino mass in cosmology: status and prospectsNov 06 2011I give an overview of the effects of neutrino masses in cosmology, focussing on the role they play in the evolution of cosmological perturbations. I discuss how recent observations of the cosmic microwave background anisotropies and the large-scale matter ... More
Direct Constraints on Minimal Supersymmetry from Fermi-LAT Observations of the Dwarf Galaxy Segue 1Sep 17 2009Dec 15 2009The dwarf galaxy Segue 1 is one of the most promising targets for the indirect detection of dark matter. Here we examine what constraints 9 months of Fermi-LAT gamma-ray observations of Segue 1 place upon the Constrained Minimal Supersymmetric Standard ... More
Cylindrically-Symmetric Solutions in Conformal GravityDec 23 2009May 27 2010Cylindrically-symmetric solutions in Conformal Gravity are investigated and several new solutions are presented and discussed. Among them, a family of vacuum solutions, generalizations of the Melvin solution and cosmic strings of the Abelian Higgs model. ... More
Superconducting and Spinning Non-Abelian Flux TubesNov 07 2007Apr 11 2008We find new non-Abelian flux tube solutions in a model of $N_f$ scalar fields in the fundamental representation of SU(N)xU(1) with $N \leq N_f$ (the ``extended non-Abelian Higgs model''), and study their main properties. Among the solutions there are ... More
Full Formula for Heavy Quarkonium Energy Levels at Next-to-next-to-next-to-leading OrderAug 24 2014Aug 26 2016We derive a full formula for the energy level of a heavy quarkonium state identified by the quantum numbers $n$, $\ell$, $s$ and $j$, up to ${\cal O}(\alpha_s^5 m)$ and ${\cal O}(\alpha_s^5 m \log \alpha_s)$ in perturbative QCD. The QCD Bethe logarithm ... More
Corrections to quarkonium 1S energy level at O(alpha_S^4 m) from non-instantaneous Coulomb vacuum polarizationDec 26 2001Jan 28 2002We calculate O(alpha_S^4 m) and O(alpha_S^4 m log(alpha_S)) corrections to the quarkonium 1S energy level analytically, which have been overlooked in recent studies. These are the contributions from one Coulomb-gluon exchange with the 1-loop vacuum polarization ... More
Off-shell Suppression of Renormalons in Non-relativistic QCD BoundstatesOct 22 2001Apr 12 2002We study an effect of the off-shellness of the quark and antiquark inside a heavy quarkonium system on IR renormalons contained in the perturbative computations of the quarkonium energy levels. We demonstrate that, when the off-shellness p_Q^2 -m_Q^2 ... More
Identification of the Early Fermi LAT Gamma-Ray Bright Objects with Extragalactic VLBI sourcesAug 28 2009Nov 10 2009A list of 205 gamma-ray strong objects was reported recently as a result of a 3-month integration with the Large Area Telescope on board the Fermi Gamma-Ray Space Telescope. We attempted identification of these objects, cross-correlating the gamma-ray ... More
Parsec-scale Jet in the Distant Gigahertz-Peaked Spectrum Quasar PKS 0858-279Jan 09 2009The high redshift GPS quasar PKS 0858-279 exhibits the following properties which make the source unusual. Our RATAN-600 monitoring of 1-22 GHz spectrum has detected broad-band radio variability with high amplitude and relatively short time scale. In ... More
Electronic State of Na_xCoO_2 Based on the Two Dimensional Triangular Lattice d-p ModelJun 05 2008The electronic state in a CoO_2 plane of the layered cobalt oxides Na_{x}CoO_2 is investigated by using the 11 band d-p model on a two-dimensional triangular lattice, where the tight-binding parameters are determined so as to fit the LDA band structure. ... More
An explanatory study of $^{11}$Li $β$ decay into $^9$Li and deuteronNov 24 1994The $\beta$-decay of $^{11}$Li into $^9$Li and {\it d} is studied using simple halo wave functions of $^{11}$Li. The sensitivity of the transition probability is elucidated on a description of the halo part and on a choice of the potential between $^9$Li ... More
T-violation tests for relativity principlesJan 23 2003We consider the implications of a violation of the equivalence principle or of Lorentz invariance in the neutrino sector for the T-asymmetry $\Delta P_T \equiv P(\nu_{\alpha} \to \nu_{\beta}) - P(\nu_{\beta} \to \nu_{\alpha})$ in a three-flavour framework. ... More
Synchronised neutrino oscillations from self interaction and associated applicationsNov 05 2002Nov 11 2002A recent revival of interest in synchronised oscillations due to neutrino--neutrino forward scattering in dense gases has led to two interesting applications with notable outcomes: (i) cosmological bounds on neutrino--antineutrino asymmetries are improved ... More
Relic neutrino asymmetry generation from $ν_α- ν_s$ oscillationsDec 08 2000Active--sterile neutrino oscillations provide a mechanism by which large differences in the neutrino and antineutrino number densities can be created in the early universe. The quantum kinetic equations are employed in the study of these asymmetries, ... More
Activators of Luminescence in Speleothems as Source of Major Mistakes in Interpretation of Luminescent Paleoclimatic RecordsSep 08 2009This work summarizes the main results of the operation of the International Program Luminescence of Cave Minerals of the commission on Physical Chemistry and Hydrogeology of Karst of UIS of UNESCO in the field of activators of speleothem luminescence. ... More
Supercurrent Interactions in Noncommutative Yang-Mills and IIB Matrix ModelNov 07 2000Jan 16 2001It is known that noncommutative Yang-Mills is equivalent to IIB matrix model with a noncommutative background, which is interpreted as a twisted reduced model. In noncommutative Yang-Mills, long range interactions can be seen in nonplanar diagrams after ... More
Models of Markov processes with a random transition mechanismAug 23 2015Oct 17 2015The paper deals with a certain class of random evolutions. We develop a construction that yields an invariant measure for a continuous-time Markov process with random transitions. The approach is based on a particular way of constructing the combined ... More
Critical Behaviour near the Mott Metal-Insulator Transition in a Two-band Hubbard ModelJul 10 2001The Mott metal-insulator transition in the two-band Hubbard model in infinite dimensions is studied by using the linearized dynamical mean-field theory. The discontinuity in the chemical potential for the change from hole to electron doping is calculated ... More
Spherical Non-Abelian Solutions in Conformal GravityOct 06 2009Feb 14 2010We study static spherically-symmetric solutions of non-Abelian gauge theory coupled to Conformal Gravity. We find solutions for the self-gravitating pure Yang-Mills case as well as monopole-like solutions of the Higgs system. The former are localized ... More
Self-Gravitating Spherical Solutions of the non-minimally coupled non-Abelian Higgs ModelDec 01 2014Motivated by the Higgs Inflation scenario, we study static spherically-symmetric solutions of the non-Abelian Higgs model coupled non-minimally to Gravity. We find solutions for the self-gravitating sphaleron as well as monopole-like solutions and study ... More
Dynamically enhanced $B\to K^*π$ decays in perturbative QCDOct 08 2002Oct 22 2002We investigate the $B \to K^{*}\pi$ decays, one of hardly understandable processes among charmless B-meson decays, within the perturbative QCD method. Owing to the dynamically enhanced mechanism in PQCD, we obtain large branching ratios and large direct ... More
New Physics Search in B Meson DecaysMar 16 2000We discuss new physics search within the minimal supergravity model by using a possible large direct CP asymmetry in $B^{\pm} \to K^{\pm}\phi, K^{0}\pi^{\pm}$ decays and B meson rare decays.
Factorization in Color-Suppressed B Meson DecaysOct 22 1998We summerize the status of factorization hypothesis in the color-suppressed B meson decays : $B \to J/\psi K^{(*)}$. We present the general formalism for decay rates and polarization fractions with considering all possible non-factorizable contributions ... More
Top mass determination and O (alpha_S^5 m) correction to toponium 1S energy levelNov 19 2002Feb 16 2003Recently the full O(alpha_S^5 m, alpha_S^5 m log(alpha_S)) correction to the heavy quarkonium 1S energy level has been computed (except the a_3-term in the QCD potential). We point out that the full correction (including the log(alpha_S)-term) is approximated ... More
Duality in the Azbel-Hofstadter problem and the two-dimensional d-wave superconductivity with a magnetic fieldJul 05 2000A single-parameter family of lattice-fermion model is constructed. It is a deformation of the Azbel-Hofstadter problem by a parameter $h={$B%((BDelta}/t$ (quantum parameter). A topological number is attached to each energy band. A duality between the ... More
Intrinsic Structure and Kinematics of the Sub-Parsec Scale Jet of M87Sep 06 2007We report new results from a sub-parsec scale study of the inner jet in M87 performed at 15 GHz with the Very Long Baseline Array. We have detected a limb brightened structure of the jet along with a faint 3 mas long counter-feature which we also find ... More
Numerical study of disorder effects on the three-dimensional Hubbard modelMay 17 2000Combined effects of interactions and disorder are investigated using a finite temperature quantum Monte Carlo technique for the three-dimensional Hubbard model with random potentials of a finite range. Temperature dependence of the charge compressibility ... More
Antiferromagnetic, Charge and Orbital Ordered States of Na0.5CoO2 Based on the Two-Dimensional Triangular Lattice d-p ModelJun 05 2008We investigate the electronic state of a CoO_2 plane in the layered cobalt oxides Na_xCoO_2 using the 11 band d-p model on a two-dimensional triangular lattice, where the tight-binding parameters are determined so as to fit the LDA band structure. Effects ... More
Exact String-Like Solutions in Conformal GravityAug 06 2010Jun 10 2011The cylindrically-symmetric static vacuum equations of Conformal Gravity are solved for the case of additional boost symmetry along the axis. We present the complete family of solutions which describe the exterior gravitational field of line sources in ... More
Tracking Simulations Near Half-Integer Resonance at PEP-IIMay 20 2003Beam-beam simulations predict that PEP-II luminosity can be increased by operating the horizontal betatron tune near and above a half-integer resonance. However, effects of the resonance and its synchrotron sidebands significantly enhance betatron and ... More
Error estimates for binomial approximations of game put optionsJun 01 2012Oct 17 2013We construct algorithms via binomial approximations for computation of prices of game put options and obtain estimates of approximation errors.
Stable and unstable cosmological models in bimetric massive gravityJul 16 2014Dec 09 2014Nonlinear, ghost-free massive gravity has two tensor fields; when both are dynamical, the mass of the graviton can lead to cosmic acceleration that agrees with background data, even in the absence of a cosmological constant. Here the question of the stability ... More
Cosmological viability of massive gravity with generalized matter couplingSep 29 2014Apr 20 2015There is a no-go theorem forbidding flat and closed FLRW solutions in massive gravity on a flat reference metric, while open solutions are unstable. Recently it was shown that this no-go theorem can be overcome if at least some matter couples to a hybrid ... More
Mott Transition in the Two-Dimensional Flux PhaseMay 16 2001Effects of the electron-electron interaction in the two-dimensional flux phase are investigated. We treat the half-filled Hubbard model with a magnetic flux $\pi$ per plaquette by the quantum Monte Carlo method. When the interaction is small, an antiferromagnetic ... More
Effects of ferromagnetic fluctuations on the electric and thermal transport properties in NaxCoO2Jun 03 2009We investigate the electronic states and the transport properties of the CoO2 plane in NaxCoO2 on the basis of the two-dimensional triangular lattice 11-band d-p model by using the fluctuation exchange approximation, where we consider the Coulomb interaction ... More
Nonconventional Polynomial CLTApr 02 2015Sep 07 2015We obtain a functional central limit theorem (CLT) for sums of the form $\xi_N(t)=\frac1{\sqrt N}\sum_{n=1}^{[Nt]}\big(F(X(q_1(n)),...,X(q_\ell(n)))-\bar F\big)$ where $q_1,...,q_\ell$ are polynomials.
Perfect Fluid Spherically-Symmetric Solutions in Massive GravityDec 08 2011Jun 20 2012We study spherically-symmetric solutions in Massive Gravity generated by matter sources with polytropic equation of state. We concentrate in the non-perturbative regime where the mass term non-linearities are important, and present the main features of ... More
Phenomenological Applications of $k_T$-Factorization (--Large Direct CP-Asymmetry in B-meson Decays--)Oct 29 2004We discuss applications of the perturbative QCD approach in the exclusive non-leptonic two body B-meson decays. We briefly review its ingredients and some important theoretical issues on the factorization approaches. PQCD results are compatible with present ... More
On the determination of the relative sign of $a_1$ and $a_2$ from polarization measurements in $B^- \rightarrow ρ^- {D^*}^o$ decaySep 26 1994Oct 05 1994We point out that polarization measurements such as the longitudinal fraction and the transverse left-right asymmetry in the Bauer-Stech-Wirbel (BSW) class III processes involving two final vector mesons, $B^- \ra \rho^- {D^*}^o$ taken as an example, ... More
Volume Preserving Diffeomorphism and Noncommutative BranesOct 06 2000We give a representation of the volume preserving diffeomorphism of $\bR^p$ in terms of the noncommutative (p-2)-branes whose kinetic term is described by the Hopf term. In the static gauge, the (p-2)-brane can be described by the free fields and it suggests ... More
Perturbative heavy quarkonium spectrum at next-to-next-to-next-to-leading orderSep 25 2013Jan 23 2014We compute the energy levels of some of the lower-lying heavy quarkonium states perturbatively up to O(alpha_s^5*m) and O(alpha_s^5*m*log[alpha_s]). Stability of the predictions depends crucially on the unknown 4-loop pole-MSbar mass relation. We discuss ... More
Higher order corrections to the large scale matter power spectrum in the presence of massive neutrinosSep 04 2008Oct 06 2008We present the first systematic derivation of the one-loop correction to the large scale matter power spectrum in a mixed cold+hot dark matter cosmology with subdominant massive neutrino hot dark matter. Starting with the equations of motion for the density ... More
Unifying treatment of nonequilibrium and unstable dynamics of cold bosonic atom system with time-dependent order parameter in Thermo Filed DynamicsJul 12 2010The coupled equations which describe the temporal evolution of the Bose-Einstein condensed system are derived in the framework of nonequilibrium Thermo Field Dynamics. The key element is that they are not the naive assemblages of presumable equations, ... More
Proca Q Tubes and their Coupling to GravityNov 06 2016The Einstein-Proca system is studied in the case of a complex vector-field self-interacting through an appropriate potential with a global U(1) symmetry. The corresponding equations for a static, cylindrically symmetric metric and matter fields are then ... More
Charge and Orbital Ordering in the Triangular-Lattice t_{2g}-Orbital System in One Dimension: A Possible Ground State of Bi_xV_8O_{16}Oct 10 2001We consider the possible charge and orbital ordering in a Hollandite compound Bi_xV_8O_{16}, which is a new one-dimensional triangular-lattice t_{2g}-orbital system. Using the strong-coupling perturbation theory, we derive the effective spin-orbit Hamiltonian ... More
Penguin Contributions in the Lifetime Difference between $B_s$ and $B_d$, and a Possible New PhysicsOct 19 1998We consider penguin contributions to the lifetime splitting between the $B_s$ and the $B_d$ meson. In the Standard Model the penguin effects are found to be opposite in sign, but of similar magnitude as the contributions of the current-current operators, ... More
Molecular-Gas Superwind from the Face-on Wolf-Rayet Galaxy MRK 1259Mar 15 1998We report results of $^{12}$CO ($J=1$-0) mapping observations of the Wolf-Rayet starburst galaxy Mrk 1259 which has optical evidence for the superwind seen from a nearly pole-on view. The CO emission is detected in the central 4 kpc region. The nuclear ... More
Normal form and solitonsJun 13 2002We present a review of the normal form theory for weakly dispersive nonlinear wave equations where the leading order phenomena can be described by the KdV equation. This is an infinite dimensional extension of the well-known Poincar\'e-Dulac normal form ... More
Superconductivity and Density Wave in the Quasi-One-Dimensional Systems: Renormalization Group StudyOct 31 2004The anisotropic superconductivity and the density wave have been investigated by applying the Kadanoff-Wilson renormalization group technique to the quasi-one-dimensional system with finite-range interactions. It is found that a temperature (T) dependence ... More
Spherical Structures in Conformal Gravity and its Scalar-Tensor ExtensionJul 11 2009Nov 24 2009We study spherically-symmetric structures in Conformal Gravity and in a scalar-tensor extension and gain some more insight about these gravitational theories. In both cases we analyze solutions in two systems: perfect fluid solutions and boson stars of ... More
O(alpha_s^5 m) quarkonium 1S spectrum in large-beta_0 approximation and renormalon cancellationJul 24 2000Nov 08 2000Presently the quarkonium spectrum, written in terms of the quark MSbar-mass, is known at O(alpha_s^3 m) accuracy. We point out that in order to achieve O(alpha_s^4 m) accuracy it is sufficient to calculate further (I) the O(alpha_s^4 m) relation between ... More
Scaling near random criticality in two-dimensional Dirac fermionsJul 02 1998Recently the existence of a random critical line in two dimensional Dirac fermions is confirmed. In this paper, we focus on its scaling properties, especially in the critical region. We treat Dirac fermions in two dimensions with two types of randomness, ... More
Analytical treatment of neutrino asymmetry equilibration from flavour oscillations in the early universeMar 19 2002Jun 05 2002A recent numerical study by A. D. Dolgov, S. H. Hansen, S. Pastor, S. T. Petcov, G. G. Raffelt, and D. V. Semikoz (DHPPRS) [hep-ph/0201287] found that complete or partial equilibrium between all active neutrino flavours can be achieved before the big ... More
Kernels for products of Hilbert L-functionsMay 07 2019We study kernel functions of L-functions and products of L-functions of Hilbert cusp forms over real quadratic fields. This extends the results on elliptic modualr forms by Diamantis and C. O'Sullivan. .
Perfect and partial hedging for swing game options in discrete timeJul 15 2009The paper introduces and studies hedging for game (Israeli) style extension of swing options considered as multiple exercise derivatives. Assuming that the underlying security can be traded without restrictions we derive a formula for valuation of multiple ... More