Results for "Ken D. Olum"

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Multi-step Fermi normal coordinatesJul 18 2012We generalize the concept of Fermi normal coordinates adapted to a geodesic to the case where the tangent space to the manifold at the base point is decomposed into a direct product of an arbitrary number of subspaces, so that we follow several geodesics ... More
Quantum inequality in spacetimes with small curvatureOct 02 2014Oct 04 2014Quantum inequalities bound the extent to which weighted time averages of the renormalized energy density of a quantum field can be negative. They have mostly been proved in flat spacetime, but we need curved-spacetime inequalities to disprove the existence ... More
Universal Doomsday: Analyzing Our Prospects for SurvivalMar 19 2013Given a sufficiently large universe, numerous civilizations almost surely exist. Some of these civilizations will be short-lived and die out relatively early in their development, i.e., before having the chance to spread to other planets. Others will ... More
Philosophical Implications of Inflationary CosmologyFeb 20 2003Oct 26 2005Recent developments in cosmology indicate that every history having a nonzero probability is realized in infinitely many distinct regions of spacetime. Thus, it appears that the universe contains infinitely many civilizations exactly like our own, as ... More
Scaling of cosmic string loopsNov 29 2005Jun 20 2006We study the spectrum of loops as a part of a complete network of cosmic strings in flat spacetime. After a long transient regime, characterized by production of small loops at the scale of the initial conditions, it appears that a true scaling regime ... More
Cosmic string formation by flux trappingJun 11 2007Aug 01 2007We study the formation of cosmic strings by confining a stochastic magnetic field into flux tubes in a numerical simulation. We use overdamped evolution in a potential that is minimized when the flux through each face in the simulation lattice is a multiple ... More
Quantum tunneling of superconducting string currentsFeb 13 2002We investigate the decay of current on a superconducting cosmic string through quantum tunneling. We construct the instanton describing tunneling in a simple bosonic string model, and estimate the decay rate. The tunneling rate vanishes in the limit of ... More
Dynamics of superconducting strings with chiral currentsApr 28 2000Mar 07 2001We rederive, using an elementary formalism, the general solution to the equations of motion for a superconducting string with a chiral (null) neutral current, earlier obtained by Carter and Peter. We apply this solution to show that the motion of such ... More
Gravitational back-reaction near cosmic string kinks and cuspsAug 24 2018Aug 31 2018We find the leading-order effect of gravitational back-reaction on cosmic strings for points near kinks and cusps. Near a kink, the effect diverges as the inverse cube root of the distance to the kink, and acts in a direction transverse to the worldsheet. ... More
New limits on cosmic strings from gravitational wave observationSep 07 2017Sep 11 2017We combine new analysis of the stochastic gravitational wave background to be expected from cosmic strings with the latest pulsar timing array (PTA) limits to give an upper bound on the energy scale of the possible cosmic string network, $G\mu < 1.5\times ... More
The Ori-Soen time machineJul 02 1999Apr 18 2000Ori and Soen have proposed a spacetime which has closed causal curves on the boundary of a region of normal causality, all within a region where the weak energy condition (positive energy density) is satisfied. I analyze the causal structure of this spacetime ... More
Entropy of Localized States and Black Hole EvaporationOct 11 1996Nov 20 1996We call a state "vacuum-bounded" if every measurement performed outside a specified interior region gives the same result as in the vacuum. We compute the maximum entropy of a vacuum-bounded state with a given energy for a one-dimensional model, with ... More
Negative Energy Densities in Quantum Field Theory With a Background PotentialNov 25 2002Dec 30 2003We present a general procedure for calculating one-loop ``Casimir'' energy densities for a scalar field coupled to a fixed potential in renormalized quantum field theory. We implement direct subtraction of counterterms computed precisely in dimensional ... More
Auxiliary variables for nonlinear equations with softly broken symmetriesNov 12 2016General methods of solving equations deal with solving N equations in N variables and the solutions are usually a set of discrete values. However, for problems with a softly broken symmetry these methods often first find a point which would be a solution ... More
Can a circulating light beam produce a time machine?Oct 17 2004In a recent paper, Mallett found a solution of the Einstein equations in which closed timelike curves (CTC's) are present in the empty space outside an infinitely long cylinder of light moving in circular paths around an axis. Here we show that, for physically ... More
Reionization from cosmic string loopsMay 18 2006Loops formed from a cosmic string network at early times would act as seeds for early formation of halos, which would form galaxies and lead to early reionization. With reasonable guesses about astrophysical and string parameters, the cosmic string scale ... More
Achronal averaged null energy conditionMay 22 2007Aug 27 2007The averaged null energy condition (ANEC) requires that the integral over a complete null geodesic of the stress-energy tensor projected onto the geodesic tangent vector is never negative. This condition is sufficient to prove many important theorems ... More
Are there Boltzmann brains in the vacuumAug 04 2010"Boltzmann brains" are human brains that arise as thermal or quantum fluctuations and last at least long enough to think a few thoughts. In many scenarios involving universes of infinite size or duration, Boltzmann brains are infinitely more common than ... More
Plate with a hole obeys the averaged null energy conditionJun 16 2005Nov 07 2005The negative energy density of Casimir systems appears to violate general relativity energy conditions. However, one cannot test the averaged null energy condition (ANEC) using standard calculations for perfectly reflecting plates, because the null geodesic ... More
Static Negative Energies Near a Domain WallMay 31 2002Dec 07 2002We show that a system of a domain wall coupled to a scalar field has static negative energy density at certain distances from the domain wall. This system provides a simple, explicit example of violation of the averaged weak energy condition and the quantum ... More
Efficient numerical solution to vacuum decay with many fieldsOct 20 2016Nov 02 2016Finding numerical solutions describing bubble nucleation is notoriously difficult in more than one field space dimension. Traditional shooting methods fail because of the extreme non-linearity of field evolution over a macroscopic distance as a function ... More
Proof of the averaged null energy condition in a classical curved spacetime using a null-projected quantum inequalityJul 01 2015Oct 27 2015Quantum inequalities are constraints on how negative the weighted average of the renormalized stress-energy tensor of a quantum field can be. A null-projected quantum inequality can be used to prove the averaged null energy condition (ANEC), which would ... More
Anomalous Observers in the Subjectively Identical Reference ClassApr 09 2013Anthropic reasoning is a critical tool to understand probabilities, especially in a large universe or multiverse. According to anthropic reasoning, we should consider ourselves typical among members of a reference class that must include all subjectively ... More
Detectability of gravitational effects of supernova neutrino emission through pulsar timingMay 16 2013May 17 2013Core-collapse supernovae emit on the order of 3x10^53 ergs in high-energy neutrinos over a time of order 10 seconds, and so decrease their mass by about 0.2 solar mass. If the explosion is nearly spherically symmetric, there will be little gravitational ... More
Dynamics of Cosmic NecklacesMay 19 2000We perform numerical simulations of cosmic necklaces (systems of monopoles connected to two strings each) and investigate the conditions under which monopoles annihilate. When the total monopole energy is large compared to the string energy, we find that ... More
Gravitational smoothing of kinks on cosmic string loopsSep 01 2016Sep 08 2016We analyze the effect of gravitational back reaction on cosmic string loops with kinks, which is an important determinant of the shape, and thus the potential observability, of string loops which may exist in the universe today. Kinks are not rounded ... More
On the size of the smallest scales in cosmic string networksMar 02 2002We present a method for the calculation of the gravitational back reaction cutoff on the smallest scales of cosmic string networks taking into account that not all modes on strings interact with all other modes. This results in a small scale structure ... More
Gravitational back reaction on piecewise linear cosmic string loopsSep 06 2016We calculate the metric and affine connection due to a piecewise linear cosmic string loop, and the effect of gravitational back reaction for the Garfinkle-Vachaspati loop with four straight segments. As expected, back reaction reduces the size of the ... More
Averaged null energy condition in a classical curved backgroundDec 11 2012The Averaged Null Energy Condition (ANEC) states that the integral along a complete null geodesic of the projection of the stress-energy tensor onto the tangent vector to the geodesic cannot be negative. Exotic spacetimes, such as those allow wormholes ... More
Efficient numerical solution to vacuum decay with many fieldsOct 20 2016Finding numerical solutions describing bubble nucleation is notoriously difficult in more than one field space dimension. Traditional shooting methods fail because of the extreme non-linearity of field evolution over a macroscopic distance as a function ... More
Electromagnetic back-reaction from currents on a straight stringMay 08 2014Jul 07 2014Charge carriers moving at the speed of light along a straight, superconducting cosmic string carry with them a logarithmically divergent slab of electromagnetic field energy. Thus no finite local input can induce a current that travels unimpeded to infinity. ... More
Quantum inequality for a scalar field with a background potentialApr 25 2014Quantum inequalities are bounds on negative time-averages of the energy density of a quantum field. They can be used to rule out exotic spacetimes in general relativity. We study quantum inequalities for a scalar field with a background potential (i.e., ... More
Energy conditions outside a dielectric ballJul 01 2004We show analytically that the vacuum electromagnetic stress-energy tensor outside a ball with constant dielectric constant and permeability always obeys the weak, null, dominant, and strong energy conditions. There are still no known examples in quantum ... More
Averaged null energy condition in spacetimes with boundariesSep 01 2006Sep 10 2007The Averaged Null Energy Condition (ANEC) requires that the average along a complete null geodesic of the projection of the stress-energy tensor onto the geodesic tangent vector can never be negative. It is sufficient to rule out many exotic phenomena ... More
UHE neutrinos from superconducting cosmic stringsJan 05 2009Nov 04 2010Superconducting cosmic strings naturally emit highly boosted charge carriers from cusps. This occurs when a cosmic string or a loop moves through a magnetic field and develops an electric current. The charge carriers and the products of their decay, including ... More
Cosmic string loop shapesAug 11 2015We analyze the shapes of cosmic string loops found in large-scale simulations of an expanding-universe string network. The simulation does not include gravitational back reaction, but we model that process by smoothing the loop using Lorentzian convolution. ... More
Gravitational backreaction simulations of simple cosmic string loopsMar 14 2019We present the results of computational gravitational backreaction on simple models of cosmic string loops. These results give us insight into the general behavior of cusps and kinks on loops, in addition to other features of evolution. Kinks are rounded ... More
Predictions for the Period Dependence of the Transition Between Rocky Super-Earths and Gaseous Sub-Neptunes and Implications for $η_{\mathrm{\oplus}}$Oct 28 2016One of the most significant advances by NASA's Kepler Mission was the discovery of an abundant new population of highly irradiated planets with sizes between that of the Earth and Neptune, unlike anything found in the Solar System. Subsequent analysis ... More
Energy-Momentum Restrictions on the Creation of Gott Time MachinesMay 01 1994The discovery by Gott of a remarkably simple spacetime with closed timelike curves (CTC's) provides a tool for investigating how the creation of time machines is prevented in classical general relativity. The Gott spacetime contains two infinitely long, ... More
Cosmic string scaling in flat spaceJan 12 2005Aug 16 2005We investigate the evolution of infinite strings as a part of a complete cosmic string network in flat space. We perform a simulation of the network which uses functional forms for the string position and thus is exact to the limits of computer arithmetic. ... More
Partial equilibration of integer and fractional edge channels in the thermal quantum Hall effectSep 14 2018Mar 01 2019Since the charged mode is much faster than the neutral modes on quantum Hall edges at large filling factors, the edge may remain out of equilibrium in thermal conductance experiments. This sheds light on the observed imperfect quantization of the thermal ... More
Reduction of CM elliptic curves and modular function congruencesDec 15 2005We study congruences of the form F(j(z)) | U(p) = G(j(z)) mod p, where U(p) is the p-th Hecke operator, j is the basic modular invariant 1/q+744+196884q+... for SL2(Z), and F,G are polynomials with integer coefficients. Using the interplay between singular ... More
The 16-fold way and the quantum Hall effect at half-integer filling factorsApr 04 2019Fractional quantum Hall states at half-integer filling factors have been observed in many systems beyond the $5/2$ and $7/2$ plateaus in GaAs quantum wells. This includes bilayer states in GaAs, several half-integer plateaus in ZnO-based heterostructures, ... More
Learning unbelievable marginal probabilitiesJun 02 2011Loopy belief propagation performs approximate inference on graphical models with loops. One might hope to compensate for the approximation by adjusting model parameters. Learning algorithms for this purpose have been explored previously, and the claim ... More
Dynamic behavior of the roots of the Taylor polynomials of the Riemann xi function with growing degreeSep 19 2016We establish a uniform approximation result for the Taylor polynomials of the xi function of Riemann which is valid in the entire complex plane as the degree grows. In particular, we identify a domain growing with the degree of the polynomials on which ... More
Tunable structures of mixtures of magnetic particles in liquid-crystalline matricesApr 16 2015We investigate the self-organization of a binary mixture of similar sized rods and dipolar soft spheres by means of Monte-Carlo simulations. We model the interparticle interactions by employing anisotropic Gay-Berne, dipolar and soft-sphere interactions. ... More
The structure of automorphic loopsOct 05 2012Automorphic loops are loops in which all inner mappings are automorphisms. This variety of loops includes, for instance, groups and commutative Moufang loops. We study uniquely 2-divisible automorphic loops, particularly automorphic loops of odd order, ... More
A maximum entropy framework for non-exponential distributionsJan 06 2015Probability distributions having power-law tails are observed in a broad range of social, economic, and biological systems. We describe here a potentially useful common framework. We derive distribution functions $\{p_k\}$ for situations in which a `joiner ... More
Detection of a 522 s Pulsation from the Transient X-ray Source Suzaku J0102.8--7204 (SXP 523) in the Small Magellanic CloudMar 01 2013During a routine calibration observation of 1E0102.2-7219 in the Small Magellanic Cloud (SMC) carried out in October 2012 for the Suzaku satellite, we detected a transient X-ray source at (RA, Dec) = (01h02m47s, -72d04m54s) in the equinox J2000.0 with ... More
Eternal inflation, black holes, and the future of civilizationsSep 08 1999May 16 2000We discuss the large-scale structure of the universe in inflationary cosmology and the implications that it may have for the long-term future of civilizations. Although each civilization is doomed to perish, it may be possible to transmit its accumulated ... More
Pseudo-Dirac Bino Dark MatterAug 29 2007Jan 08 2008While the bino-dominated lightest neutralino of the minimal supersymmetric Standard Model (MSSM) is an interesting and widely-studied candidate of the dark matter, the p-wave suppression of its annihilation cross section requires fine-tunings of the MSSM ... More
Denotational Semantics of the Simplified Lambda-Mu Calculus and a New Deduction System of Classical Type TheoryJun 21 2016Classical (or Boolean) type theory is the type theory that allows the type inference $\sigma \to \bot) \to \bot => \sigma$ (the type counterpart of double-negation elimination), where $\sigma$ is any type and $\bot$ is absurdity type. This paper first ... More
Chaotic Monte Carlo computation: a dynamical effect of random-number generationsDec 10 1998Mar 02 1999It is shown that superefficient Monte Carlo computations can be carried out by using chaotic dynamical systems as non-uniform random-number generators. Here superefficiency means that the expectation value of the square of the error decreases to 0 as ... More
Singularity analysis towards nonintegrability of nonhomogeneous nonlinear latticesApr 16 1997We show non-integrability of the nonlinear lattice of Fermi-Pasta-Ulam type via the singularity analysis(Picard-Vessiot theory) of normal variational equations of Lam\'e type.
Stable Model of X_0(125)Mar 09 2004In this paper we determine the components in the stable model of X_0(125) over C_5 by constructing in rigid-analytic terminology an explicit semi-stable covering. We then offer empirical data regarding the placement of certain CM j-invariants in the supersingular ... More
Multilinear function series and transforms in free probability theoryApr 18 2005Jun 05 2005The algebra Mul[[B]] of formal multilinear function series over an algebra B and its quotient SymMul[[B]] are introduced, as well as corresponding operations of formal composition. In the setting of Mul[[B]], the unsymmetrized R- and T-transforms of random ... More
A Robust Approximation to a Lambert-Type FunctionApr 08 2015The function $y = g(x) = \mathrm{log}\big(W(e^x)\big)$, where $W()$ denotes the Lambert W function, is the solution to the equation $y + e^y = x$. It appears in various problem situations, for instance the calculation of current-voltage curves for solar ... More
Global well-posedness of the two-dimensional exterior Navier-Stokes equations for non-decaying dataAug 23 2016We prove global well-posedness of the two-dimensional exterior Navier-Stokes equations for bounded initial data with a finite Dirichlet integral, subject to the non-slip boundary condition. As an application, we construct global solutions for asymptotically ... More
Reality, No Matter How You Slice ItOct 30 2013In order to reject the notion that information is always about something, the "It from Bit" idea relies on the nonexistence of a realistic framework that might underly quantum theory. This essay develops the case that there is a plausible underlying reality: ... More
Establishing a direct connection between detrended fluctuation analysis and Fourier analysisAug 10 2015Nov 02 2015To understand methodological features of the detrended fluctuation analysis (DFA) using a higher-order polynomial fitting, we establish the direct connection between DFA and Fourier analysis. Based on an exact calculation of the single-frequency response ... More
Lazy Transformation-Based LearningJun 03 1998We introduce a significant improvement for a relatively new machine learning method called Transformation-Based Learning. By applying a Monte Carlo strategy to randomly sample from the space of rules, rather than exhaustively analyzing all possible rules, ... More
Purely infinite, simple C*-algebras arising from free product constructions, IINov 02 1999Certain reduced free products of C*-algebras, (A,phi)=(A_1,phi_1)*(A_2,\phi_2), taken with respect to faithful states, at least one of which is not a trace, are shown to be purely infinite and simple. It is assumed that one of the A_i contain a partial ... More
Exactness of reduced amalgamated free product C*-algebrasNov 02 1999Some completely positive maps on reduced amalgamated free products of C*-algebras are constructed; these allow a proof that the class of exact unital C*-algebras is closed under taking reduced amalgamated free products. Consequently, the class of exact ... More
Experimental Outlook for the PentaquarkJul 30 2004Aug 09 2004A critical look is taken at both positive and null evidence for the $\Theta^+$ pentaquark. Potential problems with experiments will be discussed and the question of what conclusion can be drawn from both the positive and the null results is examined. ... More
Real zeroes of random polynomials, II: Descartes' rule of signs and anti-concentration on the symmetric groupJan 19 2016In this sequel to Part-I, we present a different approach to bounding the expected number of real zeroes of random polynomials with real independent identically distributed coefficients or more generally, exchangeable coefficients. We show that the mean ... More
Tropical Theta Functions and Riemann-Roch Inequality for Tropical Abelian SurfacesSep 28 2018Jan 29 2019We show that the space of theta functions on tropical tori is identified with a convex polyhedron. We also show a Riemann-Roch inequality for tropical abelian surfaces by calculating the self-intersection numbers of divisors.
Free subproducts and free scaled products of II_1 factorsMay 15 2001The constructions of free subproducts of von Neumann algebras and free scaled products are introduced, and results about them are proved, including rescaling results and results about free trade in free scaled products.
A description of amalgamated free products of finite von Neumann algebras over finite dimensional subalgebrasNov 11 2009Feb 10 2010We show that a free product of a II_1-factor and a finite von Neumann algebra with amalgamation over a finite dimensional subalgebra is always a II_1-factor, and provide an algorithm for describing it in terms of free products (with amalgamation over ... More
Global well-posedness of the two-dimensional exterior Navier-Stokes equations for non-decaying dataAug 23 2016Jul 16 2017We prove global well-posedness of the two-dimensional exterior Navier-Stokes equations for bounded initial data with a finite Dirichlet integral, subject to the non-slip boundary condition. As an application, we construct global solutions for asymptotically ... More
On estimates for the Stokes flow in a space of bounded functionsJun 20 2014Apr 21 2016In this paper, we study regularizing effects of the composition operator $S(t)\mathbb{P}\partial$ for the Stokes semigroup $S(t)$ and the Helmholtz projection $\mathbb{P}$ in a space of bounded functions. We establish new a priori $L^{\infty}$-estimates ... More
Canonical random variables for multivariate, algebra-valued distributionsDec 20 2015Jan 12 2016In the algebraic theory of algebra-valued noncommutative probability spaces, for a unital algebra B, a mild reformulation of Speicher's noncrossing B-valued cumulants for random variables in these spaces is used to construct canonical random variables, ... More
Real zeroes of random polynomials, I: Flip-invariance, Turán's lemma, and the Newton-Hadamard polygonJan 19 2016We show that with high probability the number of real zeroes of a random polynomial is bounded by the number of vertices on its Newton-Hadamard polygon times the cube of the logarithm of the polynomial degree. A similar estimate holds for zeroes lying ... More
Hyperinvariant subspaces for some B-circular operatorsMar 10 2004Apr 19 2004We show that if A is a Hilbert-space operator, then the set of all projections onto hyperinvariant subspaces of A, which is contained in the von Neumann algebra vN(A) that is generated by A, is independent of the representation of vN(A), thought of as ... More
Canonical superdiffusion and energy fluctuation divergenceOct 05 2016We propose a noble physical model obtained from a Hamiltonian with periodic potential. This model is canonical, reversible and brings about chaotic superdiffusion with energy fluctuation divergence. The analytical formula of invariant density can be obtained ... More
An HI census of Loose Groups of GalaxiesOct 03 2003We present results from our Parkes Multibeam HI survey of 3 loose groups of galaxies that are analogous to the Local Group. This is a survey of groups containing only spiral galaxies with mean separations of a few hundred kpc, and total areas of approximately ... More
The fate of formamide in a fragmenting protoplanetary discSep 26 2018Recent high-sensitivity observations carried out with ALMA have revealed the presence of complex organic molecules (COMs) such as methyl cyanide (CH$_{\rm 3}$CN) and methanol (CH$_{\rm 3}$OH) in relatively evolved protoplanetary discs. The behaviour and ... More
Uniform Asymptotics for Polynomials Orthogonal With Respect to a General Class of Discrete Weights and Universality Results for Associated Ensembles: Announcement of ResultsDec 10 2002We compute the pointwise asymptotics of orthogonal polynomials with respect to a general class of pure point measures supported on finite sets as both the number of nodes of the measure and also the degree of the orthogonal polynomials become large. The ... More
Learning to pinpoint effective operators at the LHC: a study of the $t\bar{t}b\bar{b}$ signatureOct 03 2018In the context of the Standard Model effective field theory (SMEFT), we study the LHC sensitivity to four fermion operators involving heavy quarks by employing cross section measurements in the $t\bar{t}b\bar{b}$ final state. Starting from the measurement ... More
Learning to pinpoint effective operators at the LHC: a study of the $t\bar{t}b\bar{b}$ signatureJul 05 2018Oct 17 2018In the context of the Standard Model effective field theory (SMEFT), we study the LHC sensitivity to four fermion operators involving heavy quarks by employing cross section measurements in the $t\bar{t}b\bar{b}$ final state. Starting from the measurement ... More
General scaling relations for locomotion in granular mediaApr 08 2016Mar 18 2017We derive a general dimensionless form for granular locomotion, which is validated in experiments and Discrete Element Method (DEM) simulations. The form instructs how to scale size, mass, and driving parameters in order to relate dynamic behaviors of ... More
Maximum Caliber: a general variational principle for dynamical systemsNov 09 2017We review here {\it Maximum Caliber} (Max Cal), a general variational principle for inferring distributions of paths in dynamical processes and networks. Max Cal is to dynamical trajectories what the principle of {\it Maximum Entropy} (Max Ent) is to ... More
Directly observing continuum emission from self-gravitating spiral wavesFeb 03 2016We use a simple, self-consistent, self-gravitating semi-analytic disc model to conduct an examination of the parameter space in which self-gravitating discs may exist. We then use Monte-Carlo radiative transfer to generate synthetic ALMA images of these ... More
Observation of Kinetic Isotope Effect in Electrocatalysis with Fully Deuterated Ultrapure ElectrolytesApr 26 2019Kinetic isotope effect (KIE) is a common physicochemical effect to elucidate complicated microscopic reaction mechanism in biological, chemical and physical systems. Especially, the exchange of hydrogen to deuterium is a standard approach to investigate ... More
The spectrum of basic Dirac operatorsAug 31 2009This is a survey article on a known generalization of Dirac-type operators to transverse operators called basic Dirac operators on Riemannian foliations, which are smooth foliations that have a transverse geometric structure. Construction of these operators ... More
Subfactors of free products of rescalings of a II_1-factorMar 20 2002Let Q be any II_1-factor. It is shown that any standard lattice G can be realized as the standard invariant of a free product of (several) rescalings of Q. In particular, if Q has fundamental group equal to the positive reals and if P is the free product ... More
Improvement of SNR with Chaotic Spreading Sequences for CDMAFeb 26 1999Mar 08 1999We show that chaotic spreading sequences generated by ergodic mappings of Chebyshev orthogonal polynomials have better correlation properties for CDMA(code division multiple access) than the optimal binary sequences (Gold sequences) in the sense of ensemble ... More
A class of pairwise models for epidemic dynamics on weighted networksAug 29 2012In this paper, we study the $SIS$ (susceptible-infected-susceptible) and $SIR$ (susceptible-infected-removed) epidemic models on undirected, weighted networks by deriving pairwise-type approximate models coupled with individual-based network simulation. ... More
Mechanism of Luminescence Ring Pattern Formation in Quantum Well Structures: Optically-Induced In-Plane Charge SeparationAug 07 2003Aug 07 2003About a year ago, two independent experiments [1,2], imaging indirect exciton luminescence from doped double quantum wells under applied bias and optical excitation, reported a very intriguing observation: under certain experimental conditions, the exciton ... More
Universal Features in Phonological Neighbor NetworksApr 16 2018Human speech perception involves transforming a countinous acoustic signal into discrete linguistically meaningful units, such as phonemes, while simultaneously causing a listener to activate words that are similar to the spoken utterance and to each ... More
Solvable Chaotic Synchronization -A New Interpretation of Common Noise-induced Synchronization with Conditional Lyapunov Exponents-Jun 01 2016Jul 07 2016We show the first solvable chaotic synchronization model of unidirectionally coupled dynamical systems. We establish a new interpretation of the conditional Lyapunov exponent that characterizes chaotic synchronization completely. Moreover, we newly show ... More
Numerical Approach to Maximize SNR for CDMA SystemsSep 30 2016Oct 17 2016Signal to Noise Ratio (SNR) is an important index for wireless communications. There are many methods for increasing SNR. In CDMA systems, spreading sequences are used. To increase SNR, we have to improve spreading sequences. In classical approaches, ... More
Generating functions for moments of the quasi-nilpotent DT-operatorMay 08 2002We prove a recursion formula for generating functions of certain renormalizations of *-moments of the DT(\delta_0,1)-operator T, involving an operation \odot on formal power series and a transformation E that converts \odot to usual multiplication. This ... More
Matrix product states and equivariant topological field theories for bosonic symmetry-protected topological phases in (1+1) dimensionsJul 21 2016Apr 18 2017Matrix Product States (MPSs) provide a powerful framework to study and classify gapped quantum phases --symmetry-protected topological (SPT) phases in particular--defined in one dimensional lattices. On the other hand, it is natural to expect that gapped ... More
Inversions of infinitely divisible distributions and conjugates of stochastic integral mappingsApr 09 2012The dual of an infinitely divisible distribution on $\mathbb{R}^d$ without Gaussian part defined in Sato, ALEA {\bf 3} (2007), 67--110, is renamed to the inversion. Properties and characterization of the inversion are given. A stochastic integral mapping ... More
Binary linear complementary dual codesFeb 20 2018May 18 2018Linear complementary dual codes (or codes with complementary duals) are codes whose intersections with their dual codes are trivial. We study binary linear complementary dual $[n,k]$ codes with the largest minimum weight among all binary linear complementary ... More
A Microscopic Description of the Granular Fluidity Field in Nonlocal Flow ModelingJun 28 2016A recent granular rheology based on an implicit `granular fluidity' field has been shown to quantitatively predict many nonlocal phenomena. However, the physical nature of the field has not been identified. Here, the granular fluidity is found to be a ... More
Delaunay decompositions in dimension 4Apr 29 2019May 02 2019The Voronoi cone decompositions has been attracting our attention in the compactification problem of the moduli scheme of abelian varieties. The objects to add as the boundary of the moduli scheme are stable quasi-abelian schemes, reduced or nonreduced, ... More
State Selection in Accelerated SystemsAug 27 1997The problem of state selection when multiple metastable states compete for occupation is considered for systems that are accelerated far from equilibrium. The dynamics of the supercurrent in a narrow superconducting ring under the influence of an external ... More
On the boundary behavior of the curvature of L2-metricsJul 16 2010For one-parameter degenerations of compact K\"ahler manifolds, we determine the asymptotic behavior of the first Chern form of the direct image of a Nakano semi-positive vector bundle twisted by the relative canonical bundle, when the direct image is ... More
K3 surfaces with involution, equivariant analytic torsion, and automorphic forms on the moduli space II: a structure theorem for r(M)>10Jul 16 2010We study the structure of the invariant of K3 surfaces with involution, which we obtained using equivariant analytic torsion. It was known before that the invariant is expressed as the Petersson norm of an automorphic form on the moduli space. When the ... More