Results for "André Hofmeister Serra"
total 2730took 0.12s
A mechanical autonomous stochastic heat engineJan 27 2016Stochastic heat engines are devices that generate work from random thermal motion using a small number of highly fluctuating degrees of freedom. Proposals for such devices have existed for more than a century and include the Maxwell demon and the Feynman ... More SU Uma stars: Rebrightenings after superoutburstApr 02 2015SU Uma stars after their long superoutbursts often show single or multiple rebrightenings. We show how this phenomenon can be understood as repeated reflections of transition waves which mediate changes between the hot and the cool state of the accretion ... More The formation of the coronal flow/ADAFMar 24 2003We develop a new method to describe the accretion flow in the corona above a thin disk around a black hole in vertical and radial extent. The model is based on the same physics as the earlier one-zone model, but now modified including inflow and outflow ... More A limit for the mass transfer rate in soft X-ray transientsMar 03 2000Many black hole X-ray transients are in a low state for several decades until an outburst occurs. We interpret this outburst behaviour as a marginal occurrence of a dwarf nova type disk instability in the cool outer accretion disk. We compute the disk ... More A disk in the Galactic Center in the past ?Oct 04 2004We raise the question whether in the past a disk could have existed in our Galactic Center which has disappeared now. Our model for the interaction of a cool disk and a hot corona above (Liu et al. 2004) allows to estimate an upper limit for the mass ... More The SiC problem: astronomical and meteoritic evidenceJan 11 1999Pre-solar grains of silicon carbide found in meteorites and interpreted as having had an origin around carbon stars from their isotopic composition, have all been found to be of the beta-SiC polytype. Yet to date fits to the 11.3 microns SiC emission ... More WZ Sagittae - an old dwarf novaSep 23 1998We model the evolution of the accretion disk of WZ Sagittae during the long quiescence. We find that the large amount of mass in the disk derived from the outburst luminosity is a severe constraint and demands values of $\alpha_c$ $\approx$ 0.001 in contradiction ... More Low heat conduction in white dwarf boundary layers?Mar 13 2008X-ray spectra of dwarf novae in quiescence observed by Chandra and XMM-Newton provide new information on the boundary layers of their accreting white dwarfs. Comparison of observations and models allows us to extract estimates for the thermal conductivity ... More Riemann Hypothesis and Random Walks: the Zeta caseJan 05 2016Feb 05 2016In previous work it was shown that if certain series based on sums over primes of non-principal Dirichlet characters have a conjectured random walk behavior, then the Euler product formula for its $L$-function is valid to the right of the critical line ... More Quantum critical spin liquids and superconductivity in the cupratesOct 30 2006Nov 17 2006We describe a new kind of quantum critical point in the context of quantum anti-ferromagnetism in 2d that can be understood as a quantum critical spin liquid. Based on the comparison of exponents with previous numerical work, we argue it describes a transition ... More An asymptotic upper bound on prime gapsJun 10 2015Oct 07 2015The Cram\'er-Granville conjecture is an upper bound on prime gaps, $g_n = p_{n+1} - p_n < \cCramer \, \log^2 p_n$ for some constant $\cCramer \geq 1$. Using a formula of Selberg, we first prove the weaker summed version: $\sum_{n=1}^N g_n < \sum_{n=1}^N ... More 3D Ising and other models from symplectic fermionsOct 30 2006Nov 06 2012We study a model of N component symplectic fermions in D spacetime dimensions. It has an infra-red stable fixed point in 2<D<4 dimensions referred to as Sp{2N}{D}. Based on the comparison of exponents, we conjecture that the critical exponents for the ... More The Froissart bound for inelastic cross-sectionsApr 23 2009Aug 14 2009We prove that while the total cross{}-section is bounded by $(\pi/m_\pi^2) \ln^2 s$, where $s$ is the square of the c.m. energy and $m_\pi$ the mass of the pion, the total inelastic cross{}-section is bounded by $(1/4)(\pi/m_\pi^2) \ln^2 s$, which is ... More The rigorous analyticity-unitarity program and its successesJun 16 1999We show how the combination of analyticity properties derived from local field theory and the unitarity condition (in particular positivity) leads to non-trivial physical results, including the proof of the "Froissart bound" from first principles and ... More Atomic quantum gases in periodically driven optical latticesJun 26 2016Time periodic forcing in the form of coherent radiation is a standard tool for the coherent manipulation of small quantum systems like single atoms. In the last years, periodic driving has more and more also been considered as a means for the coherent ... More On the Kodaira-Spencer map of abelian schemesJun 12 2016Let $A$ be an abelian scheme over a smooth affine complex variety $S$, $\varOmega_A$ the $\sO_S$-module of $1$-forms of the first kind on $A$, $\sD_S\varOmega_A$ the $\sD_S$-module spanned by $\varOmega_A$ in the first algebraic De Rham cohomology module, ... More Uniform sheaves and differential equationsJul 14 2012Real blow-ups and more refined "zooms" play a key role in the analysis of singularities of complex-analytic differential modules. They do not change the underlying topology, but the uniform structure. This suggests to revisit the cohomology theory of ... More Discretized Keiper/Li approach to the Riemann HypothesisMar 08 2017Jul 17 2017The Keiper--Li sequence $\{ \lambda _n \}$ is most sensitive to the Riemann Hypothesis asymptotically ($n \to \infty$), but highly elusive both analytically and numerically. We deform it to fully explicit sequences, simpler to analyze and to compute (up ... More Viterbi Algorithm Generalized for n-Tape Best-Path SearchDec 07 2006We present a generalization of the Viterbi algorithm for identifying the path with minimal (resp. maximal) weight in a n-tape weighted finite-state machine (n-WFSM), that accepts a given n-tuple of input strings (s_1,... s_n). It also allows us to compile ... More Idées galoisiennesJul 14 2012Classical applications of Galois theory concern algebraic numbers and algebraic functions. Still, the night before his duel, Galois wrote that his last mathematical thoughts had been directed toward applying his "theory of ambiguity to transcendental ... More Dynamic Logics of Dynamical SystemsMay 22 2012We survey dynamic logics for specifying and verifying properties of dynamical systems, including hybrid systems, distributed hybrid systems, and stochastic hybrid systems. A dynamic logic is a first-order modal logic with a pair of parametrized modal ... More On octahedraliy and Müntz spacesNov 05 2018We show that every M\"untz space can be written as a direct sum of Banach spaces X and Y , where Y is almost isometric to a subspace of c and X is finite dimensional. We apply this to show that no M\"untz space is locally octahedral or almost square. The Herschel View of Star FormationSep 30 2013Recent studies of the nearest star-forming clouds of the Galaxy at submillimeter wavelengths with the Herschel Space Observatory have provided us with unprecedented images of the initial conditions and early phases of the star formation process. The Herschel ... More A sharpening of Li's criterion for the Riemann HypothesisApr 10 2004Apr 15 2004Exact and asymptotic formulae are displayed for the coefficients $\lambda_n$ used in Li's criterion for the Riemann Hypothesis. In particular, we argue that if (and only if) the Hypothesis is true, $\lambda_n \sim n(A \log n +B)$ for $n \to \infty$ (with ... More Coherent pairs of measures and Markov-Bernstein inequalitiesMay 11 2016All the coherent pairs of measures associated to linear functionals $c_0$ and $c_1$, introduced by Iserles et al in 1991, have been given by Meijer in 1997. There exist seven kinds of coherent pairs. All these cases are explored in order to give three ... More Analytical analysis of Lyot coronographsNov 30 2006Dec 18 2006We derive an analytical solution to the computation of the output of a Lyot coronagraph for a given complex amplitude on the pupil plane. This solution, which does not require any simplifying assumption, relies on an expansion of the entrance complex ... More Sharpenings of Li's criterion for the Riemann HypothesisJun 16 2005Jan 25 2006Exact and asymptotic formulae are displayed for the coefficients $\lambda_n$ used in Li's criterion for the Riemann Hypothesis. For $n \to \infty$ we obtain that if (and only if) the Hypothesis is true, $\lambda_n \sim n(A \log n +B)$ (with $A>0$ and ... More Atomic quantum gases in periodically driven optical latticesJun 26 2016Nov 03 2016Time periodic forcing in the form of coherent radiation is a standard tool for the coherent manipulation of small quantum systems like single atoms. In the last years, periodic driving has more and more also been considered as a means for the coherent ... More A Uniform Substitution Calculus for Differential Dynamic LogicMar 06 2015Jul 30 2015This paper introduces a new proof calculus for differential dynamic logic (dL) that is entirely based on uniform substitution, a proof rule that substitutes a formula for a predicate symbol everywhere. Uniform substitutions make it possible to rely on ... More The Mean/Max Statistic in Extreme Value AnalysisJun 29 2016Most extreme events in real life can be faithfully modeled as random realizations from a Generalized Pareto distribution, which depends on two parameters: the scale and the shape. In many actual situations, one is mostly concerned with the shape parameter, ... More Electromagnetic absorption of quasi-1D Majorana nanowiresJun 24 2015Jul 17 2015We calculate the electromagnetic absorption cross section of long and narrow nanowires, in the so-called quasi-1D limit. We consider only two transverse bands and compute the dipole absorption cross section taking into account quasiparticle transitions ... More Quasi-particle current in planar Majorana nanowiresJun 23 2015Jul 17 2015We calculate the local quasi-particle current of a Majorana state in a planar hybrid (superconductor-semiconductor) nanowire. In absence of perpendicular components of the magnetic field the current flows in circular trajectories without a preferred orientation. ... More Two-temperature coronal flow above a thin diskApr 10 2002We extended the disk corona model (Meyer & Meyer-Hofmeister 1994; Meyer, Liu, & Meyer-Hofmeister 2000a) to the inner region of galactic nuclei by including different temperatures in ions and electrons as well as Compton cooling. We found that the mass ... More Rainbow Matchings: existence and countingApr 14 2011A perfect matching M in an edge-colored complete bipartite graph K_{n,n} is rainbow if no pair of edges in M have the same color. We obtain asymptotic enumeration results for the number of rainbow matchings in terms of the maximum number of occurrences ... More A minimization approach to hyperbolic Cauchy problemsOct 25 2013Developing an original idea of De Giorgi, we introduce a new and purely variational approach to the Cauchy Problem for a wide class of defocusing hyperbolic equations. The main novel feature is that the solutions are obtained as limits of functions that ... More Top Quark Compositeness: Feasibility and ImplicationsJun 19 2008Oct 06 2008In models of electroweak symmetry breaking in which the SM fermions get their masses by mixing with composite states, it is natural to expect the top quark to show properties of compositeness. We study the phenomenological viability of having a mostly ... More Resonant Anderson localization in segmented wiresDec 02 2015We discuss a model of random segmented wire, with linear segments of 2D wires joined by circular bends. The joining vertices act as scatterers on the propagating electron waves. The model leads to resonant Anderson localization when all segments are of ... More On the Origin of the High Helium Sequence in $ω$ CentauriJan 19 2006The blue Main Sequence (bMS) of $\omega$ Cen implies a ratio of helium to metal enrichment $\Delta Y/\Delta Z \approx 70$, which is a major enigma. We show that rotating models of low metallicity stars, which account for the anomalous abundance ratios ... More Projective Pseudodifferential Analysis and Harmonic AnalysisMay 05 2006We consider pseudodifferential operators on functions on $\R^{n+1}$ which commute with the Euler operator, and can thus be restricted to spaces of functions homogeneous of some given degree. Their symbols can be regarded as functions on a reduced phase ... More Some Riemann Hypotheses from Random Walks over PrimesSep 11 2015Apr 17 2016The aim of this article is to investigate how various Riemann Hypotheses would follow only from properties of the prime numbers. To this end, we consider two classes of $L$-functions, namely, non-principal Dirichlet and those based on cusp forms. The ... More On the $L^p$ index of spin Dirac operators on conical manifoldsJul 02 2004We compute the index of the Dirac operator on spin Riemannian manifolds with conical singularities, acting from $L^p(\Sigma^+)$ to $L^q(\Sigma^-)$ with $p,q>1$. When $1+\frac{n}{p}-\frac{n}{q}>0$ we obtain the usual Atiyah-Patodi-Singer formula, but with ... More Translating solutions to Lagrangian mean curvature flowNov 27 2007We prove some non-existence theorems for translating solutions to Lagrangian mean curvature flow. More precisely, we show that translating solutions with an $L^2$ bound on the mean curvature are planes and that almost-calibrated translating solutions ... More Stop the tests: Opinion bias and statistical testsNov 20 2016When statisticians quarrel about hypothesis testing, the debate usually focus on which method is the correct one. The fundamental question of whether we should test hypothesis at all tends to be forgotten. This lack of debate has its roots on our desire ... More The Top Mass: Interpretation and Theoretical UncertaintiesDec 11 2014Currently the most precise LHC measurements of the top quark mass are determinations of the top quark mass parameter of Monte-Carlo (MC) event generators reaching uncertainties of well below $1$ GeV. However, there is an additional theoretical problem ... More A Human-Checkable Four-Color Theorem ProofJun 06 2017Nov 09 2018This paper presents a short and simple proof of the Four-Color Theorem, which can be utterly checkable by human mathematicians, without computer assistance. The new key idea that has permitted it is presented in the Introduction. Expected reliability of communication protocolsMay 18 2017We consider the problem of sending a message from a sender $s$ to a receiver $r$ through an unreliable network by specifying in a protocol what each vertex is supposed to do if it receives the message from one of its neighbors. A protocol for routing ... More