Results for "A. De Freitas"

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Two-loop helicity amplitudes for fermion-fermion scatteringSep 03 2004We discuss the calculation of two-loop helicity amplitudes for quark-quark scattering in QCD and four-gluino scattering in N=1 supersymmetric Yang-Mills theory. We study the dependence of the results on different variants of dimensional regularization. ... More
Classification of codimension two deformations of rank two Riemannian manifoldsMar 09 2015Mar 16 2016The purpose of this work is to close the local deformation problem of rank two Euclidean submanifolds in codimension two by describing their moduli space of deformations. In the process, we provide an explicit simple representation of these submanifolds, ... More
Tidal Disruption Flares: The Accretion Disk PhaseMay 10 2011Jul 24 2011The evolution of an accretion disk, formed as a consequence of the disruption of a star by a black hole, is followed by solving numerically the hydrodynamic equations. The present investigation aims to study the dependence of resulting light curves on ... More
Two-Loop Amplitudes for Gluon Fusion into Two PhotonsSep 10 2001We present the two-loop matrix elements for the scattering of two gluons into two photons in QCD. These matrix elements will enter into improved estimates of the QCD background to Higgs production at the LHC when the Higgs decays into two photons. The ... More
Metal-rich globular clusters of the Galaxy: morphology of the helium-burning "clump," and the determination of relative ages through the "$ΔV$" methodNov 07 1995Morphological aspects of the $V, \bv$ diagram of metal-rich globular clusters are analyzed, on the basis of stellar evolution models for horizontal-branch (HB) and red giant branch stars. These have been incorporated into detailed synthetic HB models, ... More
Two-loop corrections to $gg \to γγ$Nov 21 2002An overview of the calculation of the two-loop helicity amplitudes for scattering of two gluons into two photons is presented. These matrix elements enter into the recent improved calculation of the QCD background to Higgs boson decay into a pair of photons, ... More
Higher Order Heavy Quark Corrections to Deep-Inelastic ScatteringNov 20 2014The 3-loop heavy flavor corrections to deep-inelastic scattering are essential for consistent next-to-next-to-leading order QCD analyses. We report on the present status of the calculation of these corrections at large virtualities $Q^2$. We also describe ... More
Two-Loop Helicity Amplitudes for Quark-Gluon Scattering in QCD and Gluino-Gluon Scattering in Supersymmetric Yang-Mills TheoryApr 16 2003Jan 27 2014We present the two-loop QCD helicity amplitudes for quark-gluon scattering, and for quark-antiquark annihilation into two gluons. These amplitudes are relevant for next-to-next-to-leading order corrections to (polarized) jet production at hadron colliders. ... More
Phase-Space Evolution of Dark Matter HalosJan 10 2007May 03 2009(Context) In a Universe dominated by dark matter, halos are continuously accreting mass (violently or not) and such mechanism affects their dynamical state. (Aims) The evolution of dark matter halos in phase-space, and using the phase-space density indicator ... More
PS1-10jh - a tidal disruption event with an extremely low disk temperatureDec 05 2012The cooler than expected optical-UV transient PS1-10jh detected by the Pan-STARRS1 survey is probably related to a tidal disruption event in which a He-rich stellar core remnant is implied. The evolution of bound debris during the disk phase is studied ... More
On the torsion effects of a relativistic spin fluid in early cosmologyFeb 23 2009Oct 01 2009In this work we investigate the effects of torsion in the framework of Einstein-Cartan theory in early cosmology. We study solutions for a homogeneous and isotropic relativistic Weyssenhoff spin fluid with dynamical timelike axial current, also homogeneous ... More
Visser's Massive Gravity Bimetric Theory RevisitedSep 30 2011A massive gravity theory was proposed by Visser in the late nineties. This theory, based on a backgroung metric $b_{\alpha \beta}$ and on an usual dynamical metric $g_{\alpha \beta}$ has the advantage of being free of ghosts as well as discontinuities ... More
Continuous matter creation and the acceleration of the universe: a replayDec 28 2010In a recent note (arXiv:1012.5069), the investigation performed by the present authors on the evolution of density fluctuations in an accelerated universe including matter creation was criticized. The criticism is based on the fact that the Newtonian ... More
Continuous matter creation and the acceleration of the universe: the growth of density fluctuationsJul 26 2010Cosmologies including continuous matter creation are able to reproduce the main properties of the standard $\Lambda$CDM model, in particular in cases where the particle and entropy production rates are equal. These specific models, characterized by a ... More
On the cosmological effects of the Weyssenhoff spinning fluid in the Einstein-Cartan frameworkJul 10 2009Oct 01 2009The effects of non-Riemannian structures in Cosmology have been studied long ago and are still a relevant subject of investigation. In the seventies, it was discovered that singularity avoidance and early accelerated expansion can be induced by torsion ... More
Distinguishing Majorana and Dirac Gluinos and NeutralinosSep 29 2009While gluinos and neutralinos are Majorana fermions in the MSSM, they can be Dirac fermion fields in extended supersymmetry models. The difference between the two cases manifests itself in production and decay processes at colliders. In this contribution, ... More
Status of Constraints on SupersymmetryAug 01 2008Aug 17 2008A short summary of constraints on the parameter space of supersymmetric models is given. Experimental limits from high energy colliders, electroweak precision data, flavor and Higgs physics, and cosmology are considered. The main focus is on the MSSM ... More
Higher-order electroweak corrections to the partial widths and branching ratios of the Z bosonJan 10 2014Jun 26 2014Recently, the calculation of fermionic electroweak two-loop corrections to the total width of the Z boson and hadronic Z-peak cross-section in the Standard Model has been presented in arXiv:1310.2256, where "fermionic" refers to diagrams with closed fermion ... More
Radiative corrections to co-annihilation processesMay 28 2007Sep 07 2007In co-annihilation scenarios, the weakly interacting dark matter particle (WIMP) is close in mass to another particle that can decay into the WIMP. As a result, both particles freeze out at roughly the same time in the early universe, and both contribute ... More
How to study weakly coupled neutral vector bosonsAug 10 2004A weakly coupled new neutral gauge boson, forming a narrow resonance, can be efficiently produced at e+e- colliders through radiative return processes if the collider energy is larger than the gauge boson mass. This contribution analyzes the sensitivity ... More
Two-loop fermionic electroweak corrections to the Z-boson width and production rateOct 08 2013Jan 04 2014Improved predictions for the Z-boson decay width and the hadronic Z-peak cross-section within the Standard Model are presented, based on a complete calculation of electroweak two-loop corrections with closed fermion loops. Compared to previous partial ... More
The growth of supermassive black holes fed by accretion disksAug 24 2010Sep 19 2010Supermassive black holes are probably present in the centre of the majority of the galaxies. There is a consensus that these exotic objects are formed by the growth of seeds either by accreting mass from a circumnuclear disk and/or by coalescences during ... More
Numerical evaluation of multi-loop integrals using subtraction termsMay 15 2012Oct 04 2012A formalism for the numerical integration of one- and two-loop integrals is presented. It is based on subtraction terms which remove the soft, collinear and some of the ultraviolet divergences from the integrand. The numerical integral is performed in ... More
Weakly coupled neutral gauge bosons at future linear collidersMar 29 2004A weakly coupled new neutral gauge boson forms a narrow resonance that is hard to discover directly in e+e- collisions. However, if the gauge boson mass is below the center-of-mass energy, it can be produced through processes where the effective energy ... More
Electroweak precision tests in the LHC era and Z-decay form factors at two-loop levelJun 26 2014Jul 01 2014The current status of electroweak precision tests after the discovery of the Higgs boson is reviewed, both from a phenomenological and from a theoretical point of view. Predictions for all Z-pole quantities are now available at the complete fermionic ... More
Feasibility of slepton precision measurements at a muon colliderJul 19 2011Detectors at a high-energy muon collider must be protected from the decay products of beam muons by installing shielding material around the beam pipe. In this article, the impact of these blind detector regions on new-physics signatures with invisible ... More
The Helium-Core Mass at the Helium Flash in Low-Mass Red Giant Stars: Observations and TheorySep 12 1995Sep 12 1995The method developed by Raffelt (1990a,b,c) to estimate a possible increase in the standard values of the helium-core mass at the tip of the red giant branch, $\Mc$, from properties of the color-magnitude diagrams of Galactic globular clusters is employed. ... More
Generalized Second Law and phantom Cosmology: accreting black holesSep 09 2007The accretion of phantom fields by black holes within a thermodynamic context is addressed. For a fluid violating the dominant energy condition, case of a phantom fluid, the Euler and Gibbs relations permit two different possibilities for the entropy ... More
Structures of gravitational vacuum and their role in the UniverseDec 16 2003The production of gravitational vacuum defects and their contribution in energy density of the Universe are discussed. These topological microstructures could be produced as the result of defect creation of the Universe from "nothing" as well as the result ... More
The unpolarized two-loop massive pure singlet Wilson coefficients for deep-inelastic scatteringMar 14 2019We calculate the massive two--loop pure singlet Wilson coefficients for heavy quark production in the unpolarized case analytically in the whole kinematic region and derive the threshold and asymptotic expansions. We also recalculate the corresponding ... More
The $O(α^2)$ Initial State QED Corrections to $e^+e^-$ Annihilation to a Neutral Vector Boson RevisitedJan 23 2019We calculate the non-singlet, the pure singlet contribution, and their interference term, at $O(\alpha^2)$ due to electron-pair initial state radiation to $e^+ e^-$ annihilation into a neutral vector boson in a direct analytic computation without any ... More
Two-loop massive fermionic operator matrix elements and intial state QED corrections to e^+e^- \to γ^*/Z^*Dec 08 2008We describe the calculation of the two--loop massive operator matrix elements for massive external fermions. These matrix elements are needed for the calculation of the $O(\alpha^2)$ initial state radiative corrections to $e^+e^-$ annihilation into a ... More
Diquark degrees of freedom in the EOS and the compactness of compact starsDec 06 2001We discuss the role of diquarks in constructing models of compact stars. These approaches are compared to recent claims of highly compact X-ray and isolated sources.
Equilibrium configurations for quark-diquark stars and the problem of Her X-1 massNov 20 1996We report new calculations of the physical properties of a quark-diquark plasma. A vacuum contribution is taken into account and is responsible for the appearance of a stable state at zero pressure and at a baryon density of about 2.2 times the nuclear ... More
Formation and Cosmic Evolution of Elliptical GalaxiesJan 14 2003A review of the present observational and theoretical status of elliptical galaxies is presented with the aim to clarify whether the monolithic or the hierarchical, is a more viable scenario for the origin of these structures. We describe the dynamical ... More
Dynamics of entanglement among the environment oscillators of many-body systemsMar 21 2016In this work we extend the discussion that was began in the Ref. [A. L. de Paula Jr., J. G. G. de Oliveira Jr., J. G. Peixoto de Faria, Dagoberto S. Freitas and M. C. Nemes, {\it Phys. Rev.} {\bf A89}, (2014) 022303] to deal with the dynamics of the concurrence ... More
Maxima of the Q-index: graphs with no K_s,tJul 02 2015This note presents a new spectral version of the graph Zarankiewicz problem: How large can be the maximum eigenvalue of the signless Laplacian of a graph of order $n$ that does not contain a specified complete bipartite subgraph. A conjecture is stated ... More
Supersymmetric Regularization, Two-Loop QCD Amplitudes and Coupling ShiftsFeb 28 2002Nov 17 2002We present a definition of the four-dimensional helicity (FDH) regularization scheme valid for two or more loops. This scheme was previously defined and utilized at one loop. It amounts to a variation on the standard 't Hooft-Veltman scheme and is designed ... More
Ages of Elliptical Galaxies: Single versus Multi Population InterpretationAug 17 2007New calibrations of spectrophotometric indices of elliptical galaxies as functions of spectrophotometric indices are presented, permitting estimates of mean stellar population ages and metallicities. These calibrations are based on evolutionary models ... More
Gravitational Wave Emission from Galactic Radio PulsarsApr 15 1997We consider in this work continuous gravitational wave (GW) emission from non-axisymmetric radio pulsars. We treat in some detail the observational issues related to the known radio pulsar sample with the aim of unveiling the actual number of sources ... More
The Variable Flavor Number Scheme at Next-to-Leading OrderApr 09 2018We present the matching relations of the variable flavor number scheme at next-to-leading order, which are of importance to define heavy quark partonic distributions for the use at high energy colliders such as Tevatron and the LHC. The consideration ... More
The Three Loop Two-Mass Contribution to the Gluon Vacuum PolarizationOct 12 2017We calculate the two-mass contribution to the 3-loop vacuum polarization of the gluon in Quantum Chromodynamics at virtuality $p^2 = 0$ for general masses and also present the analogous result for the photon in Quantum Electrodynamics.
Two-loop operator matrix elements for massive fermionic local twist-2 operators in QEDNov 28 2011We describe the calculation of the two--loop massive operator matrix elements with massive external fermions in QED. We investigate the factorization of the $O(\alpha^2)$ initial state corrections to $e^+e^-$ annihilation into a virtual boson for large ... More
Multi-point quasi-rational approximants for the energy eigenvalues of potentials of the form V(x)= Ax^a + Bx^bOct 13 2008Analytic approximants for the eigenvalues of the one-dimensional Schr\"odinger equation with potentials of the form $V(x)= Ax^a + Bx^b$ are found using a multi-point quasi-rational approximation technique. This technique is based on the use of the power ... More
Quark-Diquark Equations of State Models: The Role of InteractionsMar 04 2003Recent observational data suggests a high compacticity (the quotient M/R) of some "neutron" stars. Motivated by these works we revisit models based on quark-diquark degrees of freedom and address the question of whether that matter is stable against diquark ... More
Indirect search for dark matter: prospects for GLASTJan 20 2004May 13 2004Possible indirect detection of neutralino, through its gamma-ray annihilation product, by the forthcoming GLAST satellite from our galactic halo, M31, M87 and the dwarf galaxies Draco and Sagittarius is studied. Gamma-ray fluxes are evaluated for the ... More
The angular momentum of dark halos: merger and accretion effectsNov 06 2003We present new results on the angular momentum evolution of dark matter halos. Halos, from N-body simulations, are classified according to their mass growth histories into two categories: the accretion category contains halos whose mass has varied continuously ... More
New UBVRI colour distributions in E-type galaxies I.The dataJan 19 2002New colour distributions have been derived from wide field UBVRI frames for 36 northern bright elliptical galaxies and a few lenticulars. The classical linear representations of colours against log r were derived, with some improvements in the accuracy ... More
The Static Gravitational Field of a Spherically Symmetric BodyDec 07 1995We continue here the exam \cite{LuMa} of a theory of gravity that satisfies the Einstein Equivalence Principle (EEP) for any kind of matter/energy, except for the gravitational energy. This is part of a research program that intends to re-examine the ... More
On the Coupling of Gravitons to MatterDec 04 1999Using relationships between open and closed strings, we present a construction of tree-level scattering amplitudes for gravitons minimally coupled to matter in terms of gauge theory partial amplitudes. In particular, we present examples of amplitudes ... More
Maxima of the Q-index: forbidden 4-cycle and 5-cycleAug 07 2013This paper gives tight upper bounds on the largest eigenvalue q(G) of the signless Laplacian of graphs with no 4-cycle and no 5-cycle. If n is odd, let F_{n} be the friendship graph of order n; if n is even, let F_{n} be F_{n-1} with an edge hanged to ... More
Submanifolds With Homothetic Gauss Map In Codimension TwoAug 19 2014In this article we derive a complete classification of all submanifolds in space forms with codimension two for which the Gauss map is homothetic.
The role of thermal instabilities on the theoretical mass function of MACHOsNov 10 1995We analyze the primordial protogalactic gas to investigate the role of thermal instabilities in the formation of condensations that could contribute to the MACHO mass function. We find that the previrialized protogalaxy could have undergone a thermally ... More
The O(α_s^3) Heavy Flavor Contributions to the Charged Current Structure Function xF_3(x,Q^2) at Large Momentum TransferAug 06 2015We calculate the massive Wilson coefficients for the heavy flavor contributions to the non-singlet charged current deep-inelastic scattering structure function $xF_3^{W^+}(x,Q^2)+xF_3^{W^-}(x,Q^2)$ in the asymptotic region $Q^2 \gg m^2$ to 3-loop order ... More
The Velocity of Gravitational WavesFeb 28 2000We examine the propagation of gravitational waves in the new field theory of gravitation recently proposed by Novello-De Lorenci-Luciane (NDL). This examination is done on a solvable case corresponding to a spherically symmetric static configuration. ... More
Coalescence Rate of Supermassive Black Hole Binaries Derived from Cosmological Simulations: Detection Rates for LISA and ETAug 12 2011The coalescence history of massive black holes has been derived from cosmological simulations, in which the evolution of those objects and that of the host galaxies are followed in a consistent way. The present study indicates that supermassive black ... More
Deformation of Rapidly Rotating Compact StarsMar 28 1995We have developed a numerical code to study the deformation ($\varepsilon = (I_{zz}-I_{xx})/I_{zz}$, where $I_{ii}$ are the moments of inertia) of neutron stars in rapidly rotation in a fully general relativistic calculation. We have found that the deformation ... More
Gravitational Waves from Wobbling PulsarsOct 14 1994The prospects for detection of gravitational waves from precessing pulsars have been considered by constructing fully relativistic rotating neutron star models and evaluating the expected wave amplitude $h$ from a galactic source. For a "typical" neutron ... More
From Fields to TreesJul 11 2012We present new MCMC algorithms for computing the posterior distributions and expectations of the unknown variables in undirected graphical models with regular structure. For demonstration purposes, we focus on Markov Random Fields (MRFs). By partitioning ... More
Large-Flip Importance SamplingJun 20 2012We propose a new Monte Carlo algorithm for complex discrete distributions. The algorithm is motivated by the N-Fold Way, which is an ingenious event-driven MCMC sampler that avoids rejection moves at any specific state. The N-Fold Way can however get ... More
Two-Loop Helicity Amplitudes for Quark-Quark Scattering in QCD and Gluino-Gluino Scattering in Supersymmetric Yang-Mills TheorySep 01 2004We present the two-loop QCD helicity amplitudes for quark-quark and quark-antiquark scattering. These amplitudes are relevant for next-to-next-to-leading order corrections to (polarized) jet production at hadron colliders. We give the results in the `t ... More
Neural Programmer-InterpretersNov 19 2015Feb 29 2016We propose the neural programmer-interpreter (NPI): a recurrent and compositional neural network that learns to represent and execute programs. NPI has three learnable components: a task-agnostic recurrent core, a persistent key-value program memory, ... More
Testing two alternatives theories to dark matter with the Milky Way dynamicsJan 05 2015Two alternative theories to dark matter are investigated by testing their ability to describe consistently the dynamics of the Milky Way. The first one refers to a modified gravity theory having a running gravitational constant and the second assumes ... More
Recklessly Approximate Sparse CodingAug 04 2012Jan 06 2013It has recently been observed that certain extremely simple feature encoding techniques are able to achieve state of the art performance on several standard image classification benchmarks including deep belief networks, convolutional nets, factored RBMs, ... More
On q-deformed Pöschl-Teller potentialsFeb 09 1999A simple algebraic technique is developed to obtain deformed energy spectra for the P\"oschl-Teller potentials.
Intracluster Moves for Constrained Discrete-Space MCMCMar 15 2012This paper addresses the problem of sampling from binary distributions with constraints. In particular, it proposes an MCMC method to draw samples from a distribution of the set of all states at a specified distance from some reference state. For example, ... More
Asymptotic Efficiency of Deterministic Estimators for Discrete Energy-Based Models: Ratio Matching and PseudolikelihoodFeb 14 2012Standard maximum likelihood estimation cannot be applied to discrete energy-based models in the general case because the computation of exact model probabilities is intractable. Recent research has seen the proposal of several new estimators designed ... More
Proceedings of the Twenty-Eighth Conference on Uncertainty in Artificial Intelligence (2012)Jan 19 2013Aug 28 2014This is the Proceedings of the Twenty-Eighth Conference on Uncertainty in Artificial Intelligence, which was held on Catalina Island, CA August 14-18 2012.
Partial algebraization and a q-deformed harmonic oscillatorAug 13 1999Nov 01 1999From the algebraic treatment of the quasi-solvable systems, and a q-deformation of the associated $su(2)$ algebra, we obtain exact solutions for the q-deformed Schrodinger equation with a 3-dimensional q-deformed harmonic oscillator potential.
Primordial Regular Black Holes: Thermodynamics and Dark MatterMay 05 2018The possibility that dark matter particles could be constituted by extreme regular primordial black holes is discussed. Extreme black holes have zero surface temperature, and are not subjected to the Hawking evaporation process. Assuming that the common ... More
The Asymptotic 3-Loop Heavy Flavor Corrections to the Charged Current Structure Functions $F_L^{W^+-W^-}(x,Q^2)$ and $F_2^{W^+-W^-}(x,Q^2)$Sep 20 2016We calculate the massive Wilson coefficients for the heavy flavor contributions to the non-singlet charged current deep-inelastic scattering structure functions $F_L^{W^+}(x,Q^2)-F_L^{W^-}(x,Q^2)$ and $F_2^{W^+}(x,Q^2)-F_2^{W^-}(x,Q^2)$ in the asymptotic ... More
On the characteristic polynomial of Laplacian Matrices of CaterpillarsJun 19 2013The characteristic polynomials of the adjacency matrix of line graphs of caterpillars and then the characteristic polynomials of their Laplacian or signless Laplacian matrices are characterized, using recursive formulas. Furthermore, the obtained results ... More
The Three-Loop Splitting Functions $P_{qg}^{(2)}$ and $P_{gg}^{(2, N_F)}$May 03 2017We calculate the unpolarized twist-2 three-loop splitting functions $P_{qg}^{(2)}(x)$ and $P_{gg}^{(2,\rm N_F)}(x)$ and the associated anomalous dimensions using massive three-loop operator matrix elements. While we calculate $P_{gg}^{(2,\rm N_F)}(x)$ ... More
The O(α_s^3 T_F^2) Contributions to the Gluonic Operator Matrix ElementMay 16 2014The $O(\alpha_s^3 T_F^2 C_F (C_A))$ contributions to the transition matrix element $A_{gg,Q}$ relevant for the variable flavor number scheme at 3--loop order are calculated. The corresponding graphs contain two massive fermion lines of equal mass leading ... More
Phenomenology of Mirror Fermions in the Littlest Higgs Model with T-ParitySep 11 2006Little Higgs models are an interesting alternative to explain electroweak symmetry breaking without fine-tuning. Supplemented with a discrete symmetry (T-parity) constraints from electroweak precision data are naturally evaded and also a viable dark matter ... More
Learning about individuals from group statisticsJul 04 2012We propose a new problem formulation which is similar to, but more informative than, the binary multiple-instance learning problem. In this setting, we are given groups of instances (described by feature vectors) along with estimates of the fraction of ... More
Theoretical Analysis of Bayesian Optimisation with Unknown Gaussian Process Hyper-ParametersJun 30 2014Bayesian optimisation has gained great popularity as a tool for optimising the parameters of machine learning algorithms and models. Somewhat ironically, setting up the hyper-parameters of Bayesian optimisation methods is notoriously hard. While reasonable ... More
TVID: Three-loop Vacuum Integrals from Dispersion relationsFeb 09 2017TVID is a program for the numerical evaluation of general three-loop vacuum integrals with arbitrary masses. It consists of two parts. An algebraic module, implemented in Mathematica, performs the separation of the divergent pieces of the master integrals ... More
Collider searches and cosmology in the MSSM with heavy scalarsAug 22 2006In a variety of supersymmetric extensions of the Standard Model, the scalar partners of the quarks and leptons are predicted to be very heavy and beyond the reach of next-generation colliders. For instance, the realization of electroweak baryogenesis ... More
The 3-Loop Non-Singlet Heavy Flavor Contributions to the Structure Function g_1(x,Q^2) at Large Momentum TransferApr 30 2015We calculate the massive flavor non-singlet Wilson coefficient for the heavy flavor contributions to the polarized structure function $g_1(x,Q^2)$ in the asymptotic region $Q^2 \gg m^2$ to 3-loop order in Quantum Chromodynamics at general values of the ... More
A Machine Learning Perspective on Predictive Coding with PAQAug 16 2011PAQ8 is an open source lossless data compression algorithm that currently achieves the best compression rates on many benchmarks. This report presents a detailed description of PAQ8 from a statistical machine learning perspective. It shows that it is ... More
Generalized ABBA Space-Time Block CodesOct 02 2005Linear space-time block codes (STBCs) of unitary rate and full diversity, systematically constructed over arbitrary constellations for any number of transmit antennas are introduced. The codes are obtained by generalizing the existing ABBA STBCs, a.k.a ... More
Astro Unparticle PhysicsAug 31 2007Dec 10 2007We investigate the effects of all flavor blind CP-conserving unparticle operators on 5th force experiments, stellar cooling, supernova explosions and compare the limits with each other and with those obtainable from collider experiments. In general, astrophysical ... More
Corrections to Quark Asymmetries at LEPNov 23 2004The most precise measurement of the weak mixing angle sin^2(theta) at LEP is from the forward-backward asymmetry e+e- --> bbbar at the Z-pole. In this note the QED and electroweak radiative corrections to obtain the pole asymmetry from the measured asymmetry ... More
The 3-Loop Pure Singlet Heavy Flavor Contributions to the Structure Function $F_2(x,Q^2)$ and the Anomalous DimensionSep 03 2014The pure singlet asymptotic heavy flavor corrections to 3-loop order for the deep-inelastic scattering structure function $F_2(x,Q^2)$ and the corresponding transition matrix element $A_{Qq}^{(3), \sf PS}$ in the variable flavor number scheme are computed. ... More
Heavy Flavor Wilson Coefficients in Deep-Inelastic Scattering: Recent ResultsNov 21 2017We present recent analytic results for the 3-loop corrections to the massive operator matrix element $A_{Qg}^{(3)}$for further color factors. These results have been obtained using the method of arbitrarily large moments. We also give an overview on the ... More
Calculating Three Loop Ladder and V-Topologies for Massive Operator Matrix Elements by Computer AlgebraSep 28 2015Three loop ladder and $V$-topology diagrams contributing to the massive operator matrix element $A_{Qg}$ are calculated. The corresponding objects can all be expressed in terms of nested sums and recurrences depending on the Mellin variable $N$ and the ... More
3-loop Massive $O(T_F^2)$ Contributions to the DIS Operator Matrix Element $A_{gg}$Sep 04 2014Contributions to heavy flavour transition matrix elements in the variable flavour number scheme are considered at 3-loop order. In particular a calculation of the diagrams with two equal masses that contribute to the massive operator matrix element $A_{gg,Q}^{(3)}$ ... More
The Logarithmic Contributions to the O(α_s^3) Asymptotic Massive Wilson Coefficients and Operator Matrix Elements in Deeply Inelastic ScatteringMar 25 2014We calculate the logarithmic contributions to the massive Wilson coefficients for deep-inelastic scattering in the asymptotic region $Q^2 \gg m^2$ to 3-loop order in the fixed-flavor number scheme and present the corresponding expressions for the massive ... More
Two-mass three-loop effects in deep-inelastic scatteringJul 20 2018We report on recent results on the two-mass corrections for massive operator matrix elements at 2- and 3-loop orders in QCD. These corrections form the building blocks of the variable flavor number scheme. Due to the similar values of the charm and bottom ... More
Expected Coalescence Rate of Double Neutron Stars for Ground Based InterferometersJun 09 2005Jun 14 2005In this paper we present new estimates of the coalescence rate of neutron star binaries in the local universe and we discuss its consequences for the first generations of ground based interferometers. Our approach based on both evolutionary and statistical ... More
Expected coalescence rates of NS-NS binaries for laser beam interferometersOct 26 2005The coalescence rate of two neutron stars (NS) is revisited. For estimation of the number of bound NS-NS and the probability of their coalescence in a timescale $\tau$, the galactic star formation history, directly derived from observations, and the evolution ... More
Three Loop Massive Operator Matrix Elements and Asymptotic Wilson Coefficients with Two Different MassesMay 19 2017Starting at 3-loop order, the massive Wilson coefficients for deep-inelastic scattering and the massive operator matrix elements describing the variable flavor number scheme receive contributions of Feynman diagrams carrying quark lines with two different ... More
New Results on the 3-Loop Heavy Flavor Wilson Coefficients in Deep-Inelastic ScatteringDec 24 2012Jan 02 2013We report on recent results obtained for the 3-loop heavy flavor Wilson coefficients in deep-inelastic scattering (DIS) at general values of the Mellin variable $N$ at larger scales of $Q^2$. These concern contributions to the gluonic ladder-topologies, ... More
QCD and QED Corrections to Light-by-Light ScatteringSep 10 2001We present the QCD and QED corrections to the fermion-loop contributions to light-by-light scattering, gamma gamma to gamma gamma, in the ultrarelativistic limit where the kinematic invariants are much larger than the masses of the charged fermions.
The massive 3-loop operator matrix elements with two masses and the generalized variable flavor number schemeDec 03 2017We report on our latest results in the calculation of the two--mass contributions to 3--loop operator matrix elements (OMEs). These OMEs are needed to compute the corresponding contributions to the deep-inealstic scattering structure functions and to ... More
The Two-mass Contribution to the Three-Loop Gluonic Operator Matrix Element $A_{gg,Q}^{(3)}$Apr 06 2018We calculate the two-mass QCD contributions to the massive operator matrix element $A_{gg,Q}$ at $\mathcal{O} (\alpha_s^3)$ in analytic form in Mellin $N$- and $z$-space, maintaining the complete dependence on the heavy quark mass ratio. These terms are ... More
Phase Transitions in Neutron Stars and Gravitational Wave EmissionAug 26 2002We review the detectability of gravitational waves generated by oscillations excited during a phase transition from hadronic matter to deconfined quark-gluon matter in the core of a neutron star. Neutron star properties were computed using a Boguta and ... More
The Longitudinal Heavy Quark Structure Function F_{L}^{Q\bar{Q}} in the Region Q^2 \gg m^2 at O(α_s^3)Aug 02 2006The logarithmic and constant contributions to the Wilson coefficient of the longitudinal heavy quark structure function to $O(\alpha_s^3)$ are calculated using mass factorization techniques in Mellin space. The small $x$ behaviour of the Wilson coefficient ... More
Einstein's gravitational lensing and nonlinear electrodynamicsAug 09 2004May 18 2005In 1936 Einstein predicted the phenomenon presently known as gravitational lensing (GL). A prime feature of GL is the magnification, because of the gravitational field, of the star visible surface as seen from a distant observer. We show here that nonlinear ... More