Results for "Dan Feldman"

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Fast and Accurate Least-Mean-Squares SolversJun 11 2019Least-mean squares (LMS) solvers such as Linear / Ridge / Lasso-Regression, SVD and Elastic-Net not only solve fundamental machine learning problems, but are also the building blocks in a variety of other methods, such as decision trees and matrix factorizations. ... More
Generic Coreset for Scalable Learning of Monotonic Kernels: Logistic Regression, Sigmoid and moreFeb 21 2018Jun 10 2018Coreset (or core-set) in this paper is a small weighted \emph{subset} $Q$ of the input set $P$ with respect to a given \emph{monotonic} function $\phi:\REAL\to\REAL$ that \emph{provably} approximates its fitting loss $\sum_{p\in P}f(p\cdot x)$ to \emph{any} ... More
k-Means for Streaming and Distributed Big Sparse DataNov 29 2015Feb 07 2016We provide the first streaming algorithm for computing a provable approximation to the $k$-means of sparse Big data. Here, sparse Big Data is a set of $n$ vectors in $\mathbb{R}^d$, where each vector has $O(1)$ non-zeroes entries, and $d\geq n$. E.g., ... More
A Unified Framework for Approximating and Clustering DataJun 07 2011May 28 2016Given a set $F$ of $n$ positive functions over a ground set $X$, we consider the problem of computing $x^*$ that minimizes the expression $\sum_{f\in F}f(x)$, over $x\in X$. A typical application is \emph{shape fitting}, where we wish to approximate a ... More
k-Means Clustering of Lines for Big DataMar 16 2019Mar 19 2019The k-means for lines is a set of k centers (points) that minimizes the sum of squared distances to a given set of n lines in R^d. This is a straightforward generalization of the k-means problem where the input is a set of n points. Related problems minimize ... More
k-Means Clustering of Lines for Big DataMar 16 2019The k-means for lines is a set of k centers (points) that minimizes the sum of squared distances to a given set of n lines in R^d. This is a straightforward generalization of the k-means problem where the input is a set of n points. Related problems minimize ... More
Minimizing Sum of Non-Convex but Piecewise log-Lipschitz Functions using CoresetsJul 23 2018Oct 16 2018We suggest a new optimization technique for minimizing the sum $\sum_{i=1}^n f_i(x)$ of $n$ non-convex real functions that satisfy a property that we call piecewise log-Lipschitz. This is by forging links between techniques in computational geometry, ... More
Cylindric algebras of De Morgan-valued logicAug 31 2014We construct a De Morgan algebra-valued logic with quantifiers, where the truth values are in a finite De Morgan algebra, We show that there is a representation theorem of the cylindric algebra of this logic from which a completeness theorem for De Morgan ... More
Guess Free Maximization of Submodular and Linear SumsOct 09 2018We consider the problem of maximizing the sum of a monotone submodular function and a linear function subject to a general solvable polytope constraint. Recently, Sviridenko et al. (2017) described an algorithm for this problem whose approximation guarantee ... More
Coresets for Kinematic Data: From Theorems to Real-Time SystemsNov 30 2015Dec 18 2017A coreset (or core-set) of a dataset is its semantic compression with respect to a set of queries, such that querying the (small) coreset provably yields an approximate answer to querying the original (full) dataset. In the last decade, coresets provided ... More
Turning Big data into tiny data: Constant-size coresets for k-means, PCA and projective clusteringJul 12 2018We develop and analyze a method to reduce the size of a very large set of data points in a high dimensional Euclidean space R d to a small set of weighted points such that the result of a predetermined data analysis task on the reduced set is approximately ... More
Does Learning Require Memorization? A Short Tale about a Long TailJun 12 2019State-of-the-art results on image recognition tasks are achieved using over-parameterized learning algorithms that (nearly) perfectly fit the training set. This phenomenon is referred to as data interpolation or, informally, as memorization of the training ... More
Low-cost and Faster Tracking Systems Using Core-sets for Pose-EstimationNov 30 2015Jul 22 2016In the pose-estimation problem we need to align a set of $n$ markers (points in 3D space) and choose one of their n! permutations, so that the sum of squared corresponding distances to another ordered set of $n$ markers is minimized. We prove that every ... More
Provable Approximations for Constrained $\ell_p$ RegressionFeb 27 2019The $\ell_p$ linear regression problem is to minimize $f(x)=||Ax-b||_p$ over $x\in\mathbb{R}^d$, where $A\in\mathbb{R}^{n\times d}$, $b\in \mathbb{R}^n$, and $p>0$. To avoid overfitting and bound $||x||_2$, the constrained $\ell_p$ regression minimizes ... More
Real-Time EEG Classification via Coresets for BCI ApplicationsJan 02 2019A brain-computer interface (BCI) based on the motor imagery (MI) paradigm translates one's motor intention into a control signal by classifying the Electroencephalogram (EEG) signal of different tasks. However, most existing systems either (i) use a high-quality ... More
Coresets for Gaussian Mixture Models of Any ShapeJun 12 2019An $\varepsilon$-coreset for a given set $D$ of $n$ points, is usually a small weighted set, such that querying the coreset \emph{provably} yields a $(1+\varepsilon)$-factor approximation to the original (full) dataset, for a given family of queries. ... More
New Frameworks for Offline and Streaming Coreset ConstructionsDec 02 2016Let $P$ be a set (called points), $Q$ be a set (called queries) and a function $ f:P\times Q\to [0,\infty)$ (called cost). For an error parameter $\epsilon>0$, a set $S\subseteq P$ with a \emph{weight function} $w:P \rightarrow [0,\infty)$ is an $\epsilon$-coreset ... More
Coresets for Vector Summarization with Applications to Network GraphsJun 17 2017We provide a deterministic data summarization algorithm that approximates the mean $\bar{p}=\frac{1}{n}\sum_{p\in P} p$ of a set $P$ of $n$ vectors in $\REAL^d$, by a weighted mean $\tilde{p}$ of a \emph{subset} of $O(1/\eps)$ vectors, i.e., independent ... More
Dimensionality Reduction of Massive Sparse Datasets Using CoresetsMar 05 2015In this paper we present a practical solution with performance guarantees to the problem of dimensionality reduction for very large scale sparse matrices. We show applications of our approach to computing the low rank approximation (reduced SVD) of such ... More
Secure $k$-ish Nearest Neighbors ClassifierJan 22 2018Apr 30 2019In machine learning, classifiers are used to predict a class of a given query based on an existing (classified) database. Given a database S of n d-dimensional points and a d-dimensional query q, the k-nearest neighbors (kNN) classifier assigns q with ... More
Secure Search on the Cloud via Coresets and SketchesAug 19 2017\emph{Secure Search} is the problem of retrieving from a database table (or any unsorted array) the records matching specified attributes, as in SQL SELECT queries, but where the database and the query are encrypted. Secure search has been the leading ... More
High Degree Vertices and Spread of Infections in Spatially Modelled Social NetworksFeb 28 2019We examine how the behaviour of high degree vertices in a network affects whether an infection spreads through communities or jumps between them. We study two stochastic susceptible-infected-recovered (SIR) processes and represent our network with a spatial ... More
A partitioned shift-without-invert algorithm to improve parallel eigensolution efficiency in real-space electronic transportJun 02 2016We present an eigenspectrum partitioning scheme without inversion for the recently described real-space electronic transport code, TRANSEC. The primary advantage of TRANSEC is its highly parallel algorithm, which enables studying conductance in large ... More
Training Gaussian Mixture Models at Scale via CoresetsMar 23 2017Jan 15 2018How can we train a statistical mixture model on a massive data set? In this work we show how to construct coresets for mixtures of Gaussians. A coreset is a weighted subset of the data, which guarantees that models fitting the coreset also provide a good ... More
Data-Dependent Coresets for Compressing Neural Networks with Applications to Generalization BoundsApr 15 2018Feb 20 2019We present an efficient coresets-based neural network compression algorithm that sparsifies the parameters of a trained fully-connected neural network in a manner that provably approximates the network's output. Our approach is based on an importance ... More
Stability of Serrin's Problem and Dynamic Stability of a Model for Contact Angle MotionJul 21 2017Aug 24 2017We study the quantitative stability of Serrin's symmetry problem and it's connection with a dynamic model for contact angle motion of quasi-static capillary drops. We prove a new stability result which is both linear and depends only on a weak norm \[ ... More
Data-Dependent Coresets for Compressing Neural Networks with Applications to Generalization BoundsApr 15 2018May 18 2019We present an efficient coresets-based neural network compression algorithm that sparsifies the parameters of a trained fully-connected neural network in a manner that provably approximates the network's output. Our approach is based on an importance ... More
No quasi-long-range order in strongly disordered vortex glasses: a rigorous proofFeb 08 2000The paper contains a rigorous proof of the absence of quasi-long-range order in the random-field O(N) model for strong disorder in the space of an arbitrary dimensionality. This result implies that quasi-long-range order inherent to the Bragg glass phase ... More
Quasi-long-range order in nematics confined in random porous mediaDec 07 1999We study the effect of random porous matrices on the ordering in nematic liquid crystals. The randomness destroys orientational lang-range order and drives the liquid crystal into a glass state. We predict two glass phases one of which possesses quasi-long-range ... More
Energy Balance in Cell Phone Radiofrequency Radiation Exposed Mice and RatsApr 29 2019The National Toxicology Program exposed mice and rats to cell phone radiofrequency radiation. They observer cancers in male rats but not in male mice and different increases in body temperature between mice and rats using identical frequency and intensity ... More
Tight Bounds on Low-degree Spectral Concentration of Submodular and XOS functionsApr 13 2015Aug 02 2015Submodular and fractionally subadditive (or equivalently XOS) functions play a fundamental role in combinatorial optimization, algorithmic game theory and machine learning. Motivated by learnability of these classes of functions from random examples, ... More
On the Skitovich-Darmois theorem for some locally compact Abelian groupsMay 23 2018Let $X$ be a locally compact Abelian group, $\alpha_{j}, \beta_j$ be topological automorphisms of $X$. Let $\xi_1, \xi_2$ be independent random variables with values in $X$ and distributions $\mu_j$ with non-vanishing characteristic functions. It is known ... More
On a characterisation theorem for probability distributions on discrete Abelian groupsApr 11 2018Let $X$ be a countable discrete Abelian group containing no elements of order 2, $\alpha$ be an automorphism of $X$, $\xi_1$ and $\xi_2$ be independent random variables with values in the group $X$ and distributions $\mu_1$ and $\mu_2$. The main result ... More
Thermoregulation in mice, rats and humans: An insight into the evolution of human hairlessnessDec 04 2018The thermoregulation system in animals removes body heat in hot temperatures and retains body heat in cold temperatures. The better the animal removes heat, the worse the animal retains heat and visa versa. It is the balance between these two conflicting ... More
Explanation for Cancer in Rats, Mice and Humans due to Cell Phone Radiofrequency RadiationJul 22 2016Jul 19 2017Very recently, the National Toxicology Program reported a correlation between exposure to whole body 900 MHz radiofrequency radiation and cancer in the brains and hearts of Sprague Dawley male rats. This paper proposes the following explanation for these ... More
Almost Optimal Semi-streaming Maximization for k-Extendible SystemsJun 11 2019In this paper we consider the problem of finding a maximum weight set subject to a $k$-extendible constraint in the data stream model. The only non-trivial algorithm known for this problem to date---to the best of our knowledge---is a semi-streaming $k^2(1 ... More
High probability generalization bounds for uniformly stable algorithms with nearly optimal rateFeb 27 2019Algorithmic stability is a classical approach to understanding and analysis of the generalization error of learning algorithms. A notable weakness of most stability-based generalization bounds is that they hold only in expectation. Generalization with ... More
Spin current and rectification in one-dimensional electronic systemsOct 30 2006Apr 02 2007Spin and charge currents can be generated by an ac voltage through a one-channel quantum wire with strong electron interactions in a static uniform magnetic field. In a certain range of low voltages, the spin current can grow as a negative power of the ... More
An Unbiased Estimator of Peculiar Velocity with Gaussian Distributed Errors for Precision CosmologyNov 24 2014We introduce a new estimator of the peculiar velocity of a galaxy or group of galaxies from redshift and distance estimates. This estimator results in peculiar velocity estimates which are statistically unbiased and that have errors that are Gaussian ... More
Whittaker unitary dual of affine graded Hecke algebras of type EAug 29 2007Sep 22 2008This paper gives the classification of the Whittaker unitary dual for affine graded Hecke algebras of type E. By the Iwahori-Matsumoto involution, this is equivalent also to the classification of the spherical unitary dual for type E. This work completes ... More
Particle-hole symmetry without particle-hole symmetry in the quantum Hall effect at ν = 5/2Mar 11 2016Aug 12 2016Numerical results suggest that the quantum Hall effect at {\nu} = 5/2 is described by the Pfaffian or anti-Pfaffian state in the absence of disorder and Landau level mixing. Those states are incompatible with the observed transport properties of GaAs ... More
Detecting non-Abelian Statistics with Electronic Mach-Zehnder InterferometerJul 21 2006Oct 26 2006Fractionally charged quasiparticles in the quantum Hall state with filling factor $\nu=5/2$ are expected to obey non-Abelian statistics. We demonstrate that their statistics can be probed by transport measurements in an electronic Mach-Zehnder interferometer. ... More
Global Solutions of Shock Reflection by Large-Angle Wedges for Potential FlowAug 19 2007When a plane shock hits a wedge head on, it experiences a reflection-diffraction process and then a self-similar reflected shock moves outward as the original shock moves forward in time. Experimental, computational, and asymptotic analysis has shown ... More
Shock Reflection-Diffraction Phenomena and Multidimensional Conservation LawsJun 06 2009When a plane shock hits a wedge head on, it experiences a reflection-diffraction process, and then a self-similar reflected shock moves outward as the original shock moves forward in time. The complexity of reflection-diffraction configurations was first ... More
An empirical template library of stellar spectra for a wide range of spectral classes, luminosity classes, and metallicities using SDSS BOSS spectraFeb 22 2017Mar 22 2017We present a library of empirical stellar spectra created using spectra from the Sloan Digital Sky Survey's Baryon Oscillation Spectroscopic Survey (BOSS). The templates cover spectral types O5 through L3, are binned by metallicity from -2.0 dex through ... More
Topology Of Real And Angle Valued Maps And Graph Representations (A Brief Survey)May 20 2012(lecture delivered at the Congress of the Romanian mathematicians, Brasov, June 2011) Using graph representations a new class of computable topological invariants associated with a tame real or angle valued map were recently introduced, providing a theory ... More
Elliptically distributed lozenge tilings of a hexagonOct 19 2011We present a detailed study of a 4 parameter family of elliptic weights on tilings of a hexagon introduced by Borodin, Gorin and Rains, and generalize some of their results. In the process, we connect the combinatorics of the model with the theory of ... More
Diffusion of Confidential Information on NetworksJan 01 2011Mar 11 2011This is a natural generalization of the previous work by Dan, "Modeling and Simulation of Diffusion Phenomena on Social Networks," to appear in The proceedings of 2011 Third International Conference on Computer Modeling and Simulation. In this paper, ... More
The expectation value of the field operatorJul 14 2014Much of the mathematical development of quantum field theory has been in support of determining the S-matrix in order to calculate scattering cross sections. However there is also an interest in determining how expectation values of field operators evolve ... More
One-W-type modules for rational Cherednik algebra and cuspidal two-sided cellsMar 26 2015Mar 30 2015We classify the simple modules for the rational Cherednik algebra that are irreducible when restricted to W, in the case when W is a finite Weyl group. The classification turns out to be closely related to the cuspidal two-sided cells in the sense of ... More
A refinement of Betti numbers in the presence of a continuous function, ( I )Jan 05 2015Dec 27 2015We propose a refinement of the Betti numbers and of the homology with coefficients in a field of a compact ANR in the presence of a continuous real valued function. The refinement of Betti numbers consists of finite configurations of points with multiplicities ... More
Taming the divergent terms that occur during adiabatic switching in perturbation theoryJun 21 2016Aug 30 2016A potential problem with adiabatic switching in perturbation theory is that divergent terms appear in the series solution. An example of this was presented by C. Brouder et al [4] for a simple 2 state system where the evolution of system in the presence ... More
Faster Projection-free Convex Optimization over the SpectrahedronMay 20 2016Minimizing a convex function over the spectrahedron, i.e., the set of all positive semidefinite matrices with unit trace, is an important optimization task with many applications in optimization, machine learning, and signal processing. It is also notoriously ... More
A note on stability of spacecrafts and underwater vehiclesMar 01 2016A Hamilton-Poisson system is an approach for the motion of a spacecraft around an asteroid or for the motion of an underwater vehicle. We construct a coordinate chart on the symplectic leaf which contains a specific generic equilibrium point and we establish ... More
Nonequivalence of Controllability Properties for Piecewise Linear Markov Switch ProcessesOct 06 2016In this paper we study the exact null-controllability property for a class of controlled PDMP of switch type with switch-dependent, piecewise linear dynamics and multiplicative jumps. First, we show that exact null-controllability induces a con-trollability ... More
Poincaré duality of wonderful compactifications and tautological ringsJan 20 2015Sep 24 2015Let $g \geq 2$. Let $M_{g,n}^{rt}$ be the moduli space of $n$-pointed genus $g$ curves with rational tails. Let $C_g^n$ be the $n$-fold fibered power of the universal curve over $M_g$. We prove that the tautological ring of $M_{g,n}^{rt}$ has Poincar\'e ... More
A Case for Radio Galaxies as the Sources of IceCube's Astrophysical Neutrino FluxMay 20 2016May 24 2016We present an argument that radio galaxies (active galaxies with mis-aligned jets) are likely to be the primary sources of the high-energy astrophysical neutrinos observed by IceCube. In particular, if the gamma-ray emission observed from radio galaxies ... More
Detecting MeV Gauge Bosons With High-Energy Neutrino TelescopesJan 23 2007If annihilating MeV-scale dark matter particles are responsible for the observed 511 keV emission from the Galactic bulge, then new light gauge bosons which mediate the dark matter annihilations may have other observable consequences. In particular, if ... More
Inflation and the Higgs ScalarDec 05 2014This note makes a self-contained exposition of the basic facts of big bang cosmology as they relate to inflation. The fundamental problems with that model are then explored. A quartic scalar potential model of inflation is evaluated which provides the ... More
Hot Hands, Streaks and Coin-flips: Numerical Nonsense in the New York TimesDec 29 2015The existence of "Hot Hands" and "Streaks" in sports and gambling is hotly debated, but there is no uncertainty about the recent batting-average of the New York Times: it is now two-for-two in mangling and misunderstanding elementary concepts in probability ... More
Explicit reduction theory for SU(2,1;Z[i])Jan 04 2006Let Gamma\D be an arithmetic quotient of a symmetric space of non-compact type. A spine D_0 is a Gamma-equivariant deformation retraction of D with dimension equal to the virtual cohomological dimension of Gamma. We explicitly construct a spine for the ... More
The Schlesinger System and the Riemann-Hilbert ProblemSep 16 2003We generalize some classical results for the Schlesinger system of partial differential equations and give the explicit form of its solution, associated with rational matrix functions in general position.
On the number of n-dimensional representations of SU(3), the Bernoulli numbers, and the Witten zeta functionMar 12 2015Oct 04 2016We derive new results about properties of the Witten zeta function associated with the group SU(3), and use them to prove an asymptotic formula for the number of n-dimensional representations of SU(3) counted up to equivalence. Our analysis also relates ... More
On a Gauss-Kuzmin-Type Problem for a Family of Continued Fraction ExpansionsAug 17 2011Apr 01 2013In this paper we study in detail a family of continued fraction expansions of any number in the unit closed interval $[0,1]$ whose digits are differences of consecutive non-positive integer powers of an integer $m \geq 2$. For the transformation which ... More
On a Gauss-Kuzmin Type Problem for a Family of Continued FractionsOct 23 2010Sep 18 2013We study a family of continued fraction expansion of reals from the unit interval. The Perron-Frobenius operator of the transformation which generates this expansion under the invariant measure of this transformation is given. Using the ergodic behavior ... More
Dependence with complete connections and the Gauss-Kuzmin theorem for N-continued fractionsOct 13 2015We consider a family $\{T_N:N \geq 1 \}$ of interval maps as generalizations of the Gauss transformation. For the continued fraction expansion arising from $T_N$, we solve its Gauss-Kuzmin-type problem by applying the theory of random systems with complete ... More
Noether-Lefschetz locus and generalisation of an example due to MumfordSep 21 2014In this article we generalise the well-known example due to Mumford for a generically non-reduced component of the Hilbert scheme of curves in $\mathbb{P}^3$ whose general element is smooth. The example considers smooth curves in smooth cubic surfaces ... More
A refinement of Betti numbers in the presence of a continuous function. ( I )Jan 05 2015Jun 27 2017We propose a refinement of the Betti numbers and of the homology with coefficients in a field of a compact ANR in the presence of a continuous real valued function. The refinement of Betti numbers consists of finite configurations of points with multiplicities ... More
Representation of One as the Sum of Unit FractionsFeb 23 2009Apr 15 2009One is expressed as the sum of the reciprocals of a certain set of integers. We give an elegant proof to the fact applying the polynomial theorem and basic calculus.
Network, cluster coordinates and N = 2 theory II: Irregular singularityJul 25 2012Cluster coordinates for a large class of Argyres-Douglas and asymptotical free theories are constructed using network on bordered Riemann surface. Such N = 2 theories are engineered using six dimensional (2, 0) theory on Riemann surface with irregular ... More
Polynomial maps with nilpotent Jacobians in dimension three IOct 08 2017In this paper, we first prove that $u,v,h$ are linearly dependent over ${\bf K}$ if $JH$ is nilpotent and $H$ has the form: $H=(u(x,y,z),v(u,h),h(x,y))$ with $H(0)=0$ or $H=(u(x,y),v(u,h),h(x,y,z))$ with $H(0)=0$. Then we classify polynomial maps of the ... More
On simple derivations and the group of polynomial automorphismsAug 23 2018Sep 10 2018In the paper, we first give an equivalent statement about $\operatorname{Aut}({\bf K}[x_1,\ldots,x_n])_D=\{id\}$ and some properties of $D$ if $D$ is a simple derivation. Then we study the subgroup of ${\bf K}$-automorphisms of ${\bf K}[x_1,\ldots,x_n]$ ... More
Bott--Kitaev periodic table and index theoryOct 04 2017We consider topological insulators and superconductors with discrete symmetries and clarify the relevant index theory behind the periodic table proposed by Kitaev. An effective Hamiltonian determines the analytical index, which can be computed by a topological ... More
Degeneration at $E_2$ of Certain Spectral SequencesJan 19 2016We propose a Hodge theory for the spaces $E_2^{p,\,q}$ featuring at the second step either in the Fr\"olicher spectral sequence of an arbitrary compact complex manifold $X$ or in the spectral sequence associated with a pair $(N,\,F)$ of complementary ... More
Transcendental Kähler Cohomology ClassesJan 03 2012Associated with a smooth, $d$-closed $(1, 1)$-form $\alpha$ of possibly non-rational De Rham cohomology class on a compact complex manifold $X$ is a sequence of asymptotically holomorphic complex line bundles $L_k$ on $X$ equipped with $(0, 1)$-connections ... More
Notes on Actions of Sets and Groups and Generalized Affine SpacesJul 13 2016Nov 17 2016Some well-known and less well-known or new notions related to group actions are surveyed. Some of these notions are used to generalize affine spaces. Actions are seen as functions with values in transformation monoids
The Taylor coefficients of the Jacobi theta constant $θ_3$Jul 16 2018Oct 17 2018We study the Taylor expansion around the point $x=1$ of a classical modular form, the Jacobi theta constant $\theta_3$. This leads naturally to a new sequence $(d(n))_{n=0}^\infty=1,1,-1,51,849,-26199,\ldots$ of integers, which arise as the Taylor coefficients ... More
Higher order matching polynomials and d-orthogonalitySep 09 2009Nov 16 2009We show combinatorially that the higher-order matching polynomials of several families of graphs are d-orthogonal polynomials. The matching polynomial of a graph is a generating function for coverings of a graph by disjoint edges; the higher-order matching ... More
Periodic points in random substitution subshiftsAug 17 2018We study various aspects of periodic points for random substitution subshifts. In order to do so, we introduce a new property for random substitutions called the disjoint images condition. We provide a procedure for determining the property for compatible ... More
Projections and Phase retrievalJun 01 2015We characterize collections of orthogonal projections for which it is possible to reconstruct a vector from the magnitudes of the corresponding projections. As a result we are able to show that in an $M$-dimensional real vector space a vector can be reconstructed ... More
Equivariant geometry and the cohomology of the moduli space of curvesJun 11 2010Aug 05 2011In this expository article we give a categorical definition of the integral cohomology ring of a stack. We show that for quotient stacks the categorical cohomology may be identified with equivariant cohomology. Via this identification we show that for ... More
Compactifying normal algebraic spacesSep 18 2007Sep 20 2007The author wrote this note after being asked about the existence of compactifications of algebraic spaces. Subsequent to posting the article to the math arXiv, the author learned from Yutakaa Matsuura that the results of this paper had been proved by ... More
Supernova Rates in Galaxy ClustersJan 23 2005Measurements of SN rates in different environments and redshifts can shed light on the nature of SN-Ia progenitors, star formation history, and chemical enrichment history. I summarize some recent work by our group in this area, and discuss the implications. ... More
Limits on Dust in Rich Clusters of Galaxies from the Color of Background QuasarsAug 20 1995I measure the V-I color distribution of two samples of radio-selected quasars. Quasars from one sample are projected on the sky within 1 degree of a rich foreground Abell cluster of galaxies, while quasars from the other sample are more than 3 degrees ... More
On the fraction of intermediate-mass close binaries that explode as type-Ia supernovaeJul 31 2007Nov 09 2007Type-Ia supernovae (SNe-Ia) are thought to result from a thermonuclear runaway in white dwarfs (WDs) that approach the Chandrasekhar limit, either through accretion from a companion or a merger with another WD. I compile observational estimates of the ... More
Ultraviolet Imaging and Spectroscopy of LINERsDec 12 1995I review the UV properties of LINERs (low-ionization nuclear emission-line regions), based mostly on the recent {\it HST} UV imaging survey of nearby galaxies by Maoz et al. (1995). 25 of the galaxies in the northern subsample host a LINER nucleus. Six ... More
Factorization in color-suppressed B -> D(*)0 pi0 decays from the soft-collinear effective theoryNov 08 2004The soft-collinear effective theory has been recently applied to prove novel factorization theorems for many B decays. We describe here in some detail the factorization relation for color-supressed nonleptonic B -> D(*)0 pi0 decays and update the phenomenological ... More
Bound on $\cosα$ from exclusive weak radiative B decaysJun 28 2000We present a bound on the weak phase $\alpha$ from isospin-breaking effects in weak radiative decays, which requires the CP-averaged branching ratios for the weak radiative decays $B^\pm\to \rho^\pm \gamma$, $B^0\to \rho^0/\omega \gamma$, $B\to K^* \gamma$ ... More
Probing New Physics with b -> sγDecaysJul 08 2002In the Standard Model, the photon emitted in b->s\gamma decays is predicted to be left-handed polarized. We discuss the types of New Physics which can produce a deviation from this prediction, focusing on the Minimal Supersymmetric Standard Model. A new ... More
Bifurcation scenario to Nikolaevskii turbulence in small systemsApr 14 2005We show that the chaos in Kuramoto-Sivashinsky equation occurs through period-doubling cascade (Feigenbaum scenario), in contrast, the chaos in Nikolaevskii equation occurs through torus-doubling bifurcation (Ruelle-Takens-Newhouse scenario).
Formation of Li I lines in photospheric granulationAug 21 1997Aug 27 1997The possibility of significant systematic errors due to the use of 1D homogeneous atmospheres in lithium-abundance determinations of cool stars motivates a study of non-local-thermodynamic-equilibrium (NLTE) effects on Li I line formation in a 3D solar-granulation ... More
A NLTE study of neutral boron in solar-type starsJan 12 1994The formation of the resonance lines of neutral boron in solar-type stellar atmospheres is investigated taking into account effects of departures from local thermodynamic equilibrium (NLTE effects). The latter are due to a combination of overionisation ... More
Thompson's Group F and Uniformly Finite HomologyJun 17 2008Mar 11 2009This paper demonstrates the uniformly finite homology developed by Block and Weinberger and its relationship to amenable spaces via applications to the Cayley graph of Thompson's Group F. In particular, a certain class of subgraph of F is shown to be ... More
Semiconductor ThermistorsMar 10 2005Semiconductor thermistors operating in the variable range hopping conduction regime have been used in thermal detectors of all kinds for more than fifty years. Their use in sensitive bolometers for infrared astronomy was a highly developed empirical art ... More
Dirt, Gravity, and Lunar-Based Telescopes: The Value Proposition for AstronomyFeb 16 2007The lunar surface has historically been considered an optimal site for a broad range of astronomical telescopes. That assumption, which has come to be somewhat reflexive, is critically examined in this paper and found to be poorly substantiated. The value ... More
Nuclear beta-decay measurements and |Vud|Aug 11 2011Some recent work in nuclear beta decay related to the value of |Vud| is described along with some near-term goals for future measurements.
New invariants for a real valued and angle valued map (an Alternative to Morse- Novikov theory)May 24 2016This paper but section 6 is essentially my lecture at The Eighth Congress of Romanian Mathematicians, June 26 - July 1, 2015, Iasi, Romania. The paper summarizes the definitions and the properties of the invariants associated to a real or an angle valued ... More
Renormalization group flow, Entropy and EigenvaluesApr 07 2016The irreversibility of the renormalization group flow is conjectured to be closely related to the concept of entropy. In this paper, the variation of eigenvalues under the renormalization group flow will be studied. Based on the one-loop approximation ... More
On representations attached to generic level p Harder congruencesMay 11 2016We investigate the interplay between Galois and automorphic representations coming from generic Harder type congruences for degree 2 Siegel modular forms. Using Local Langlands results for GSp4 we see conditions that guarantee the existence of a level ... More
Deriving Z[J] from the time evolution operatorMay 30 2014An important quantity in quantum field theory is the vacuum-to-vacuum transition amplitude in the presence of an external source. This quantity is often designated by Z[J] and is the generator for the n-point Greens functions. In textbooks Z[J] is often ... More