Results for "Per Bjerkeli"

total 977took 0.09s
Externally heated protostellar cores in the Ophiuchus star-forming regionNov 21 2016We present APEX 218 GHz observations of molecular emission in a complete sample of embedded protostars in the Ophiuchus star-forming region. To study the physical properties of the cores, we calculate H$_2$CO and c-C$_3$H$_2$ rotational temperatures, ... More
Externally heated protostellar cores in the Ophiuchus star-forming regionNov 21 2016Nov 22 2016We present APEX 218 GHz observations of molecular emission in a complete sample of embedded protostars in the Ophiuchus star-forming region. To study the physical properties of the cores, we calculate H$_2$CO and c-C$_3$H$_2$ rotational temperatures, ... More
Dark mammoth trunks in the merging galaxy NGC 1316 and a mechanism of cosmic double helicesMar 30 2010NGC 1316 is a giant, elliptical galaxy containing a complex network of dark, dust features. The morphology of these features has been examined in some detail using a Hubble Space Telescope, Advanced Camera for Surveys image. It is found that most of the ... More
Density-functional theory of nonequilibrium tunnelingJul 28 2008Aug 03 2008Nanoscale optoelectronics and molecular-electronics systems operate with current injection and nonequilibrium tunneling, phenomena that challenge consistent descriptions of the steady-state transport. The current affects the electron-density variation ... More
Dynamics of Anti-de Sitter Domain WallsOct 18 1999Oct 26 1999We study solutions corresponding to moving domain walls in the Randall-Sundrum universe. The bulk geometry is given by patching together black hole solutions in AdS$_5$, and the motion of the wall is determined from the junction equations. Observers on ... More
Spin-Orbit Interaction from Matrix TheorySep 28 1997Oct 27 1997We study the leading order spin dependence of graviton scattering in eleven dimensions, and show that the results obtained from supergravity and from Matrix Theory precisely agree.
On the effect of pruning on the singularity structure of zeta functionsJun 13 1996We investigate the topological zeta function for unimodal maps in general and dynamical zeta functions for the tent map in particular. For the generic situation, when the kneading sequence is aperiodic, it is shown that the zeta functions have a natural ... More
On the duality between periodic orbit statistics and quantum level statisticsFeb 01 1995We discuss consequences of a recent observation that the sequence of periodic orbits in a chaotic billiard behaves like a poissonian stochastic process on small scales. This enables the semiclassical form factor $K_{sc}(\tau)$ to agree with predictions ... More
Lyapunov exponents and anomalous diffusion of a Lorentz gas with infinite horizon using approximate zeta functionsJan 02 1995We compute the Lyapunov exponent, generalized Lyapunov exponents and the diffusion constant for a Lorentz gas on a square lattice, thus having infinite horizon. Approximate zeta functions, written in terms of probabilities rather than periodic orbits, ... More
Spin Glasses: Model systems for non-equilibrium dynamicsSep 26 2003Spin glasses are frustrated magnetic systems due to a random distribution of ferro- and antiferromagnetic interactions. An experimental three dimensional (3d) spin glass exhibits a second order phase transition to a low temperature spin glass phase regardless ... More
Magnetic Vortices in High Temperature SuperconductorsFeb 05 2001Feb 06 2001It is suggested that modes, observed in recent neutron scattering experiments by Lake {\it et al.}, on La$_{2-x}$Sr$_x$CuO$_4$ in strong magnetic fields ($\approx$ 7 T), are due to the existence of antiferromagnetic moments associated with the cores of ... More
Non-thermal aspects of black hole radianceAug 04 1995The phenomenon of black hole thermodynamics raises several deep issues which any proper theory of quantum gravity must confront: to what extent does the inclusion of the back-reaction alter the thermal character of the radiation, how can the entropy be ... More
Approximate zeta functions for the Sinai billiard and related systemsFeb 24 1994We discuss zeta functions, and traces of the associated weighted evolution operators for intermittent Hamiltonian systems in general and for the Sinai billiard in particular. The intermittency of this billiard is utilized so that the zeta functions may ... More
Multiphasic profiles for voltage-dependent K+ channels: Reanalysis of data of MacKinnon and coworkersJun 09 2016In a study of the role that voltage-dependent K+ channels may have in the mechanosensation of living cells (Schmidt et al. Proc Soc Natl Acad Sci USA 109: 10352-10357. 2012), the data were as conventionally done fitted by a Boltzmann function. However, ... More
Profiles for voltage-activated currents are multiphasic, not curvilinearMar 16 2016Data for voltage-activation of a potassium channel (Matulef et al. Proc Natl Acad Sci USA 110: 17886-17891. 2013) were, as conventionally done, fitted by the authors by a Boltzmann function, i.e. by a curvilinear profile. Reanalysis of the data reveals ... More
A strict epistemic approach to physicsJan 04 2016Apr 23 2016The general view is that all fundamental physical laws should be formulated within the framework given by quantum mechanics (QM). In a sense, QM therefore has the character of a metaphysical theory. Consequently, if it is possible to derive QM from more ... More
Multiphasic pH profiles for the reaction of tris-(hydroxymethyl)-aminomethane with phenyl estersDec 08 2015Reanalysis of data (Bruice and York 1961) for the pH dependences of the calculated apparent second-order rate constants (k2) for the reaction of tris-(hydroxymethyl)-aminomethane (TRIS) with phenyl esters reveals that the pH profiles are consistently ... More
Generalizing the Markov and covariance interpolation problem using input-to-state filtersApr 07 2011In the Markov and covariance interpolation problem a transfer function $W$ is sought that match the first coefficients in the expansion of $W$ around zero and the first coefficients of the Laurent expansion of the corresponding spectral density $WW^\star$. ... More
Improved Inapproximability For Submodular MaximizationApr 21 2010We show that it is Unique Games-hard to approximate the maximum of a submodular function to within a factor 0.695, and that it is Unique Games-hard to approximate the maximum of a symmetric submodular function to within a factor 0.739. These results slightly ... More
The AdS(4) x CP(3) string and its Bethe equations in the near plane wave limitNov 17 2008Nov 23 2008We perform a detailed study of bosonic type IIA string theory in a large light-cone momentum / near plane wave limit of $AdS_4 \times CP_3$. In order to attain this we derive the Hamiltonian up to cubic and quartic order in number of fields and calculate ... More
Notes on formal deformations of quantum planes and universal enveloping algebrasNov 30 2018Feb 05 2019In these notes, we introduce formal hom-associative deformations of the quantum planes and the universal enveloping algebras of the two-dimensional non-abelian Lie algebras. We then show that these deformations induce formal hom-Lie deformations of the ... More
From chaotic to disordered systems - a periodic orbit approachFeb 26 1998We apply periodic orbit theory to a quantum billiard on a torus with a variable number N of small circular scatterers distributed randomly. Provided these scatterers are much smaller than the wave length they may be regarded as sources of diffraction. ... More
First determination of the electric charge of the top quarkFeb 01 2007In this thesis, the first determination of the electric charge of the top quark is presented using 370pb-1 of data recorded by the D0 detector at the Fermilab Tevatron accelerator. ttbar events are selected with one isolated electron or muon and at least ... More
Three-Neutrino MSW Effect and the Lehmann Mass MatrixOct 22 2002Recent work on analytical solutions to the MSW equations for three neutrino flavours is reviewed, with emphasis on the exponential density. Application to a particular mass matrix, proposed by Lehmann, Newton and Wu, is also discussed. Within this model, ... More
Spin(p+1,p+1) Covariant Dp-brane Bound StatesNov 30 2000We construct Spin(p+1,p+1) covariant Dp-brane bound states by using that the potentials in the RR sector of toroidically compactified type II supergravity transform as a chiral spinor of the T-duality group. As an application, we show the invariance of ... More
Hawking Radiation from Black Holes Formed During Quantum TunnelingMar 28 1994Mar 28 1994We study the behaviour of scalar fields on background geometries which undergo quantum tunneling. The two examples considered are a moving mirror in flat space which tunnels through a potential barrier, and a false vacuum bubble which tunnels to form ... More
Surface assembly and ultrafast operation of all-nanoscale resonant-tunneling transistorsSep 01 2003Oct 12 2011Realization of a robust nanotube-heterostructure tunneling transistors [Solid State Comm. 116, p. 569 (2000)] requires the difficult formation [Science 293, p. 76 (2001)] of a central nanoscale barrier separating a pair of outside metallic leads. Here ... More
Model of Outgrowths in the Spiral Galaxies NGC 4921 and NGC 7049 and the Origin of Spiral ArmsNov 15 2012NGC 4921 and 7049 are two spiral galaxies presenting narrow, distinct dust features. A detailed study of the morphology of those features has been carried out using Hubble Space Telescope archival images. NGC 4921 shows a few but well-defined dust arms ... More
Postulates for and measurements in Everett's quantum mechanicsMar 03 2016Mar 20 2016Everetts Relative State Interpretation (aka Many Worlds Interpretation) has gained increasing interest due the progress understanding the role of decoherence. In order to fullfil its promise as an intellectually economic realistic description of the physical ... More
Discontinuous transitions: Multiphasic profiles for channels, binding, pH, folding and chain lengthNov 20 2015Dec 07 2015A wide variety of biological as well as non-biological processes and phenomena involving ion channels, binding, pH, folding/unfolding and effects of chain length are well represented by multiphasic profiles, a series of straight lines separated by discontinuous ... More
Discriminants, symmetrized graph monomials, and sums of squares certificatesFeb 02 2012Here we present certificates for 5 classes of 6-edged multigraphs whose symmetrized graph monomials may be represented as sum of squares, but not as linear combinations of partition square graphs. This is a complement to the results presented in Discriminants, ... More
On eigenvalues of the Schrödinger operator with an even complex-valued polynomial potentialApr 04 2011In this paper, we generalize several results of the article "Analytic continuation of eigenvalues of a quartic oscillator" of A. Eremenko and A. Gabrielov. We consider a family of eigenvalue problems for a Schr\"odinger equation with even polynomial potentials ... More
Anomalies at high temperatureFeb 23 1998The anomaly equation can be derived from the ultraviolet properties of quantum field theory and should, therefore, not depend on infrared properties, such as the presence of a thermal heat bath. There is also an infrared explanation of anomalies which ... More
Dispersion relations from the Hard Thermal Loop effective action in a magnetic fieldOct 17 1995Dispersion relations for fermions at high temperature and in a background magnetic field are calculated in two different ways. First from a straightforward one-loop calculation where, in the weak field limit, we find an expression closely related to the ... More
Non-symmetric Macdonald polynomials and Demazure-Lusztig operatorsFeb 16 2016Apr 15 2016We extend the family non-symmetric Macdonald polynomials and define general-basement Macdonald polynomials. We show that these also satisfy a triangularity property with respect to the monomials bases and behave well under the Demazure-Lusztig operators. ... More
Gelfand-Tsetlin polytopes and the integer decomposition propertyMay 19 2014Nov 25 2015Let $P$ be the Gelfand--Tsetlin polytope defined by the skew shape $\lambda/\mu$ and weight $w$. In the case corresponding to a standard Young tableau, we completely characterize for which shapes $\lambda/\mu$ the polytope $P$ is integral. Furthermore, ... More
Renormalization of Oscillator Lattices with DisorderApr 13 2009A real-space renormalization transformation is constructed for lattices of non-identical oscillators with dynamics of the general form $d\phi_{k}/dt=\omega_{k}+g\sum_{l}f_{lk}(\phi_{l},\phi_{k})$. The transformation acts on ensembles of such lattices. ... More
Escape from intermittent repellers- Periodic orbit theory for crossover from exponential to algebraic decayMar 18 1999May 18 1999We apply periodic orbit theory to study the asymptotic distribution of escape times from an intermittent map. The dynamical zeta function exhibits a branch point which is associated with an asymptotic power law escape. By an analytic continuation technique ... More
The role of singularities in chaotic spectroscopyDec 12 1996We review the status of the semiclassical trace formula with emphasis on the particular types of singularities that occur in the Gutzwiller-Voros zeta function for bound chaotic systems. To understand the problem better we extend the discussion to include ... More
Decay of correlations, Lyapunov exponents and anomalous diffusion in the Sinai billiardNov 02 1995We compute the decay of the velocity autocorrelation function, the Lyapunov exponent and the diffusion constant for the Sinai billiard within the framework of dynamical zeta functions. The asymptotic decay of the velocity autocorrelation function is found ... More
Periodic orbit asymptotics for intermittent Hamiltonian systemsJun 17 1994We address the problems in applying cycle expansions to bound chaotic systems, caused by e.g. intermittency and incompleteness of the symbolic dynamics. We discuss zeta functions associated with weighted evolution operators and in particular a one-parameter ... More
On the worldsheet theory of the type IIA AdS(4) x CP(3) superstringSep 03 2009Mar 19 2010We perform a detailed study of the type IIA superstring in AdS(4) x CP(3). After introducing suitable bosonic light-cone and fermionic kappa worldsheet gauges we derive the pure boson and fermion SU(2|2) x U(1) covariant light-cone Hamiltonian up to quartic ... More
Interference Alignment (IA) and Coordinated Multi-Point (CoMP) overheads and RF impairments: testbed resultsJan 14 2014Mar 16 2014In this work we investigate the network MIMO techniques of interference alignment (IA) and fully adaptive joint transmission coordinated multipoint (CoMP) in an indoor very small cell environment. Our focus is on the overheads in a system with quantized ... More
Worldsheet two- and four-point functions at one loop in AdS(3) / CFT(2)Mar 06 2014Apr 12 2014In this note we study worldsheet two- and four-point functions at the one-loop level for the type IIA superstring in AdS(3) x S(3) x M(4) . We first address the regularization ambiguity that appears in the dispersion relation derived from integrability. ... More
Derivatives as an IR Regulator for Massless FieldsMar 24 1995The free propagator for the scalar $\lambda \phi^4$--theory is calculated exactly up to the second derivative of a background field. Using this propagator I compute the one--loop effective action, which then contains all powers of the field but with at ... More
Polytopes and large counterexamplesSep 02 2016Sep 08 2016In this short note, we give large counterexamples to natural questions about certain order polytopes, in particular, Gelfand--Tsetlin polytopes. Several of the counterexamples are too large to be discovered via a brute-force computer search. We also show ... More
Stretched skew Schur polynomials are recurrentOct 01 2012We show that sequences of skew Schur polynomials obtained from stretched semi-standard Young tableaux satisfy a linear recurrence, which we give explicitly. Using this, we apply this to finding certain asymptotic behavior of these Schur polynomials and ... More
The Lyapunov exponent in the Sinai billiard in the small scatterer limitJan 11 1996We show that Lyapunov exponent for the Sinai billiard is $\lambda = -2\log(R)+C+O(R\log^2 R)$ with $C=1-4\log 2+27/(2\pi^2)\cdot \zeta(3)$ where $R$ is the radius of the circular scatterer. We consider the disk-to-disk-map of the standard configuration ... More
Lectures on black holes and the AdS_3 / CFT_2 correspondenceSep 11 2006Sep 20 2006We present a detailed discussion of AdS_3 black holes and their connection to two-dimensional conformal field theories via the AdS/CFT correspondence. Our emphasis is on deriving refined versions of black hole partition functions, that include the effect ... More
The ATLAS b-Jet TriggerNov 17 2011The online event selection is crucial to reject most of the events containing uninteresting background collisions while preserving as much as possible the interesting physical signals. The b-jet selection is part of the trigger strategy of the ATLAS experiment ... More
Approximative Covariance InterpolationApr 11 2011When methods of moments are used for identification of power spectral densities, a model is matched to estimated second order statistics such as, e.g., covariance estimates. If the estimates are good there is an infinite family of power spectra consistent ... More
'Perfectly' curvilinear profiles for binding as determined by ITC may in fact be multiphasicJun 29 2016In a structural analysis of the proteasome activator PafE in Mycobacterium tuberculosis, the binding of the activator or shorter constructs to the 20S proteasome core particle (20S CP) or derivatives was measured by isothermal titration calorimetry (Bai ... More
Everett's Missing Postulate and the Born RuleFeb 14 2019Feb 15 2019Everett's Relative State Interpretation (aka Many Worlds Interpretation) has gained increasing interest due to the progress understanding the role of decoherence. In order to fulfill its promise as a realistic description of the physical world, two postulates ... More
Combinatorial proof of the skew K-saturation theoremJul 15 2013Jun 27 2014We give a combinatorial proof of the skew Kostka analogue of the K-saturation theorem. More precisely, for any positive integer k, we give an explicit injection from the set of skew semistandard Young tableaux with skew shape k\lambda/k\mu{} and type ... More
On the density of rational and integral points on algebraic varietiesAug 17 2005Mar 13 2006We prove a conjecture of Heath-Brown on the number of rational points of bounded height for a large class of projective varieties.
Introduction to the method of multiple scalesDec 12 2013Apr 07 2016Earlier versions of these lecture notes have been used at the Cork Summerschool on Theory and Mathematics Modelling of Ultrashort Pulse Propagation (2013), and as a part of a graduate course in the theory of nonlinear waves in the period 2014-2016. This ... More
Multiphasic interactions between nucleotides and target proteinsAug 26 2016The nucleotides guanosine tetraphosphate (ppGpp) and guanosine pentaphosphate (pppGpp) bind to target proteins to promote bacterial survival (Corrigan et al. 2016). Thus, the binding of the nucleotides to RsgA, a GTPase, inhibits the hydrolysis of GTP. ... More
Competing interaction in magnets: the root of ordered disorder or only frustration?Nov 06 2013What does the equilibrium atomic, molecular or spin configuration of a glass phase look like? Is there only one unique equilibrium configuration or are there infinitely many configurations of equal energy? The processes and mechanisms governing the path ... More
Interference Alignment (IA) and Coordinated Multi-Point (CoMP) with IEEE802.11ac feedback compression: testbed resultsNov 05 2013Feb 19 2014We have implemented interference alignment (IA) and joint transmission coordinated multipoint (CoMP) on a wireless testbed using the feedback compression scheme of the new 802.11ac standard. The performance as a function of the frequency domain granularity ... More
Nonequilibrium thermodynamics of interacting tunneling transport: variational grand potential, density-functional formulation, and nature of steady-state forcesAug 23 2011Oct 09 2012The standard formulation of tunneling transport rests on an open-boundary modeling. There, conserving approximations to nonequilibrium Green function or quantum-statistical mechanics provide consistent but computational costly approaches; alternatively, ... More
Do zeta functions for intermittent maps have branch points?Sep 19 1996We present numerical evidence that the dynamical zeta function and the Fredholm determinant of intermittent maps with a neutral fix point have branch point singularities at z=1 We consider the power series expansion of zeta function and the Fredholm determinant ... More
Resonance spectra and a periodic orbit sum rule for bound chaotic systemsAug 12 1993We consider the spectrum of the evolution operator for bound chaotic systems by evaluating its trace. This trace is known to approach unity as $t \rightarrow \infty$ for bound systems. It is written as the Fourier transform of the logaritmic derivative ... More
Schur polynomials, banded Toeplitz matrices and Widom's formulaAug 28 2012We prove that for arbitrary partitions $\mathbf{\lambda} \subseteq \mathbf{\kappa},$ and integers $0\leq c<r\leq n,$ the sequence of Schur polynomials $S_{(\mathbf{\kappa} + k\cdot \mathbf{1}^c)/(\mathbf{\lambda} + k\cdot \mathbf{1}^r)}(x_1,...,x_n)$ ... More
Hard thermal loops in a magnetic field and the chiral anomalyAug 08 1996The fermionic dispersion relation in the presence of a background magnetic field and a high temperature QED plasma is calculated exactly in the external field, using the Hard Thermal Loop effective action. As the field strength increases there is a smooth ... More
Polynomials defined by tableaux and linear recurrencesMay 11 2015May 28 2015We show that several families of polynomials defined via fillings of diagrams satisfy linear recurrences under a natural operation on the shape of the diagram. We focus on key polynomials, (also known as Demazure characters), and Demazure atoms. The same ... More
Everett's Missing Postulate and the Born RuleFeb 14 2019Everett's Relative State Interpretation (aka Many Worlds Interpretation) has gained increasing interest due to the progress understanding the role of decoherence. In order to fulfill its promise as a realistic description of the physical world, two postulates ... More
Stringy corrections to Kahler potentials, SUSY breaking, and the cosmological constant problemAug 06 2004Feb 10 2005The moduli of N=1 compactifications of IIB string theory can be stabilized by a combination of fluxes (which freeze complex structure moduli and the dilaton) and nonperturbative superpotentials (which freeze Kahler moduli), typically leading to supersymmetric ... More
Higher Spin Gravity Amplitudes From Zero-form ChargesAug 19 2012Feb 11 2013We examine zero-form charges in Vasiliev's four-dimensional bosonic higher spin gravities. These are classical observables given by integrals over noncommutative twistor space of adjoint combinations of the zero-form master fields, including insertions ... More
Families of exact solutions to Vasiliev's 4D equations with spherical, cylindrical and biaxial symmetryJul 06 2011Oct 24 2011We provide Vasiliev's four-dimensional bosonic higher-spin gravities with six families of exact solutions admitting two commuting Killing vectors. Each family contains a subset of generalized Petrov Type-D solutions in which one of the two so(2) symmetries ... More
Understanding adhesion at as-deposited interfaces from ab initio thermodynamics of deposition growth: thin-film alumina on titanium carbideSep 06 2010We investigate the chemical composition and adhesion of chemical vapour deposited thin-film alumina on TiC using and extending a recently proposed nonequilibrium method of ab initio thermodynamics of deposition growth (AIT-DG) [Rohrer J and Hyldgaard ... More
Complex Behavior in Simple Models of Biological CoevolutionSep 08 2006We explore the complex dynamical behavior of simple predator-prey models of biological coevolution that account for interspecific and intraspecific competition for resources, as well as adaptive foraging behavior. In long kinetic Monte Carlo simulations ... More
On the decay of correlations in Sinai billiards with infinite horizonJan 18 1996We compute the decay of the autocorrelation function of the observable $|v_x|$ in the Sinai billiard and of the observable $v_x$ in the associated Lorentz gas with an approximation due to Baladi, Eckmann and Ruelle. We consider the standard configuration ... More
Effect of Self-Interaction on Charged Black Hole RadianceNov 29 1994We extend our previous analysis of the modification of the spectrum of black hole radiance due to the simplest and probably most quantitatively important back-reaction effect, that is self-gravitational interaction, to the case of charged holes. As anticipated, ... More
Gluino Production in Electron-Positron AnnihilationJul 14 1994We discuss the pair production of gluinos in electron-positron annihilation at LEP, in a model with soft supersymmetry breaking, allowing for mixing between the squarks. In much of the parameter space of the Minimal Supersymmetric Model (MSSM) the cross ... More
A Simple Stationary Line Element for the Schwarzschild Geometry, and Some ApplicationsJun 23 1994Jun 27 1994Guided by a Hamiltonian treatment of spherically symmetric geometry, we find a remarkably simple -- stationary, but not static -- form for the line element of Schwarzschild (and Reissner-Nordstrom) geometry. The line element continues smoothly through ... More
D-brane Dynamics in the c=1 Matrix ModelAug 06 2003Sep 15 2003Recent work has shown that unstable D-branes in two dimensional string theory are represented by eigenvalues in a dual matrix model. We elaborate on this proposal by showing how to systematically include higher order effects in string perturbation theory. ... More
Vacuum and MSW interpretations of solar neutrino data with the LNW mass matrixJun 29 2000Jul 14 2000The Lehmann-Newton-Wu mass matrix, which was recently applied to neutrinos, is further investigated. The analytic results presented earlier are confirmed numerically for the solar density profile of the Standard Solar Model. The combined analysis of atmospheric ... More
On the existence of doubling measures with certain regularity propertiesApr 14 1998Given a compact pseudo-metric space, we associate to it upper and lower dimensions, depending only on the metric. Then we construct a doubling metric for which the measure of a dillated ball is closely related to these dimensions.
Determining the CP of a Higgs Particle at a Future Linear ColliderAug 03 1995In a more general electroweak theory, there could be Higgs particles that are odd under $CP$. Correlations among momenta of the initial electron and final-state fermions are in the Bjorken process sensitive to the $CP$ parity. Monte Carlo data on the ... More
Signals of $CP$ violation in Higgs decayFeb 26 1994We consider an extension of the Standard Model where some Higgs particle is not an eigenstate of $CP$, and discuss the possibility of extracting signals of the resulting $CP$ violation. In the case of Higgs decay to four fermions we study correlations ... More
A methodology for using Kalman filter to determine material parameters from uncertain measurementsFeb 12 2015A Kalman filter can be used to determine material parameters using uncertain experimental data. However, starting with inappropriate initial values for material parameters might include false local attractors or even divergence. Also, inappropriate choices ... More
The low energy limit of the AdS(3) x S(3) x M(4) spinning stringJun 28 2013We derive the low-energy effective action for the spinning (GKP) string in AdS(3) x S(3) x M(4) where M(4) = S(3) x S(1) or T(4). In the first case the action consists of two O(4) non-linear sigma models which are coupled through their interaction with ... More
Non-Gaussianity in String Cosmology: A Case StudyOct 15 2010We study non-gaussianity effects, using the $\delta N$ formalism, in a multi-field inflationary model consisting of K\"ahler moduli derived from type IIB string compactification in the large volume limit. The analytical work in this paper mostly follows ... More
Structure and binding in crystals of cage-like molecules: hexamine and platonic hydrocarbonsOct 07 2010In this paper, we show that first-principle calculations using a van der Waals density functional (vdW-DF), [Phys. Rev. Lett. $\mathbf{92}$, 246401 (2004)] permits determination of molecular crystal structure. We study the crystal structures of hexamine ... More
A Fiber Approach to Harmonic Analysis of Unfolded Higher-Spin Field EquationsJun 11 2008Sep 01 2008In Vasiliev's unfolded formulation of higher-spin dynamics the standard fields are embedded on-shell into covariantly constant master fields valued in Lorentz-covariant slices of the star-product algebra A of functions on the singleton phase space. Correspondingly, ... More
Three Charge Supertubes and Black Hole HairFeb 19 2004Mar 31 2004We construct finite size, supersymmetric, tubular D-brane configurations with three charges, two angular momenta and several brane dipole moments. In type IIA string theory these are tubular configurations with D0, D4 and F1 charge, as well as D2, D6 ... More
Democratic Reinforcement: Learning via Self-OrganizationJan 23 1996The problem of learning in the absence of external intelligence is discussed in the context of a simple model. The model consists of a set of randomly connected, or layered integrate-and fire neurons. Inputs to and outputs from the environment are connected ... More
The Thermal Beta-Function in Yang-Mills TheoryAug 09 1994Previous calculations of the thermal beta-function in a hot Yang--Mills gas at the one--loop level have exposed problems with the gauge dependence and with the sign, which is opposite to what one would expect for asymptotic freedom. We show that inclusion ... More
Stability of large scale chromomagnetic fields in the early universeJun 10 1998Sep 20 1998It is well known that Yang-Mills theory in vacuum has a perturbative instability to spontaneously form a large scale magnetic field (the Savvidy mechanism) and that a constant field is unstable so that a possible ground state has to be inhomogenous over ... More
An Entropy Formula for Higher Spin Black Holes via Conical SingularitiesFeb 06 2013Mar 19 2013We consider the entropy of higher spin black holes in 2+1 dimensions using the conical singularity approach. By introducing a conical singularity along a non contractible cycle and carefully evaluating its contribution to the Chern Simons action, we derive ... More
S-duality in AdS/CFT magnetohydrodynamicsJul 16 2009We study the nonlinear hydrodynamics of a 2+1 dimensional charged conformal fluid subject to slowly varying external electric and magnetic fields. Following recent work on deriving nonlinear hydrodynamics from gravity, we demonstrate how long wavelength ... More
Tuned Two-Higgs-Doublet ModelDec 10 2010We consider a Two-Higgs-Doublet Model (2HDM) constrained by the condition that assures cancellation of quadratic divergences up to the leading two-loop order. Regions in the parameter space consistent with existing experimental constraints and with the ... More
A major-index preserving map on fillingsMar 09 2017Mar 21 2017We generalize a map by S. Mason regarding two combinatorial models for key polynomials, in a way that accounts for the major index. We also define similar variants of this map, that regards alternative models for the modified Macdonald polynomials at ... More
On the Moser-Trudinger inequality in complex spaceAug 24 2018In this paper we prove the pluricomplex counterpart of the Moser-Trudinger and Sobolev inequalities in complex space. We consider these inequalities for plurisubharmonic functions with finite pluricomplex energy, and we estimate the concerned constants. ... More
Randomized methods for matrix computations and analysis of high dimensional dataJul 06 2016This report surveys a number of randomized techniques that have recently been proposed for computing matrix factorizations and for analyzing high dimensional data sets. It presents some modifications to algorithms that have previously been published that ... More
Non-Commutative Instantons and the Seiberg-Witten MapOct 03 2001Jun 11 2002We present several results concerning non-commutative instantons and the Seiberg-Witten map. Using a simple ansatz we find a large new class of instanton solutions in arbitrary even dimensional non-commutative Yang-Mills theory. These include the two ... More
Multi-Field Inflation from String TheoryDec 08 2009We construct a multi-field inflationary model consisting of multiple K\"ahler moduli derived from type IIB string compactification in the large volume limit. The model consists of both heavy and light fields, with the former being frozen during the inflationary ... More
Sensitivity to temperature perturbations of the ageing states in a re-entrant ferromagnetSep 03 1998Dynamic magnetic properties and ageing phenomena of the re-entrant ferromagnet (Fe0.20Ni0.80)75P16B6Al3 are investigated by time dependent zero field cooled magnetic relaxation, m (t), measurements. The influence of a temperature cycling (perturbation), ... More
Fluctuations in models of biological macroevolutionFeb 28 2005Fluctuations in diversity and extinction sizes are discussed and compared for two different, individual-based models of biological coevolution. Both models display power-law distributions for various quantities of evolutionary interest, such as the lifetimes ... More
Light-Gluino Production at LEPNov 08 1994Nov 10 1994If gluinos are light, they will be produced in electron-positron annihilation at LEP, not only by radiation in pairs off quarks and antiquarks, but also without accompanying quark and antiquark jets. We here discuss the latter process, pair production ... More