Results for "Harri Niemi"

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Constraints from $v_2$ fluctuations for the initial state geometry of heavy-ion collisionsJan 09 2014The ability to accurately compute the series of coefficients $v_n$ characterizing the momentum space anisotropies of particle production in ultrarelativistic heavy ion collisions as a function of centrality is widely regarded as a triumph of fluid dynamics ... More
Non-resistive dissipative magnetohydrodynamics from the Boltzmann equation in the 14-moment approximationApr 14 2018Oct 14 2018We derive the equations of motion of relativistic, non-resistive, second-order dissipative magnetohydrodynamics from the Boltzmann equation using the method of moments. We assume the fluid to be composed of a single type of point-like particles with vanishing ... More
Elliptic flow from event-by-event hydrodynamicsJun 22 2011We present an event-by-event hydrodynamical framework which takes into account the initial density fluctuations arising from a Monte Carlo Glauber model. The elliptic flow is calculated with the event plane method and a one-to-one comparison with the ... More
Closing the equations of motion of anisotropic fluid dynamics by a judicious choice of moment of the Boltzmann equationJun 29 2016In Moln\'ar et al. [Phys. Rev. D 93, 114025 (2016)] the equations of anisotropic dissipative fluid dynamics were obtained from the moments of the Boltzmann equation based on an expansion around an arbitrary anisotropic single-particle distribution function. ... More
Closing the equations of motion of anisotropic fluid dynamics by a judicious choice of moment of the Boltzmann equationJun 29 2016Dec 02 2016In Moln\'ar et al. [Phys. Rev. D 93, 114025 (2016)] the equations of anisotropic dissipative fluid dynamics were obtained from the moments of the Boltzmann equation based on an expansion around an arbitrary anisotropic single-particle distribution function. ... More
Elliptic flow from event-by-event hydrodynamics with fluctuating initial stateDec 01 2010We develop an event-by-event ideal hydrodynamical framework where initial state density fluctuations are present and where we use a similar flow-analysis method as in the experiments to make a one-to-one $v_2$ comparison with the measured data. Our studies ... More
Event-by-event hydrodynamics and elliptic flow from fluctuating initial stateJul 02 2010Jan 26 2011We develop a framework for event-by-event ideal hydrodynamics to study the differential elliptic flow which is measured at different centralities in Au+Au collisions at Relativistic Heavy Ion Collider (RHIC). Fluctuating initial energy density profiles, ... More
Efficient Bayesian inference in stochastic chemical kinetic models using graphical processing unitsJan 21 2011A goal of systems biology is to understand the dynamics of intracellular systems. Stochastic chemical kinetic models are often utilized to accurately capture the stochastic nature of these systems due to low numbers of molecules. Collecting system data ... More
Examination of directed flow as a signature of the softest point of the equation of state in QCD matterJan 28 2016Sep 26 2016We analyze the directed flow of protons and pions in high-energy heavy-ion collisions in the incident energy range from $\sqrt{s_{{\scriptscriptstyle NN}}}=7.7$ to 27 GeV within a microscopic transport model. Standard hadronic transport approaches do ... More
Influence of temperature dependent shear viscosity on elliptic flow at back- and forward rapidities in ultrarelativistic heavy-ion collisionsJul 30 2014Nov 12 2014We explore the influence of a temperature-dependent shear viscosity over entropy density ratio $\eta/s$ on the azimuthal anisotropies v_2 and v_4 of hadrons at various rapidities. We find that in Au+Au collisions at full RHIC energy, $\sqrt{s_{NN}}=200$ ... More
Latest results from the EbyE NLO EKRT modelApr 13 2017We review the results from the event-by-event next-to-leading order perturbative QCD + saturation + viscous hydrodynamics (EbyE NLO EKRT) model. With a simultaneous analysis of LHC and RHIC bulk observables we systematically constrain the QCD matter shear ... More
Resistive dissipative magnetohydrodynamics from the Boltzmann-Vlasov equationFeb 05 2019We derive the equations of motion of relativistic, resistive, second-order dissipative magnetohydrodynamics from the Boltzmann-Vlasov equation using the method of moments. We thus extend our previous work [Phys. Rev. D 98, 076009 (2018)], where we only ... More
Correlated gluonic hot spots meet symmetric cumulants data at LHC energiesJul 16 2018We present a systematic study on the influence of spatial correlations between the proton constituents, in our case gluonic hot spots, their size and their number on the symmetric cumulant SC(2,3), at the eccentricity level, within a Monte Carlo Glauber ... More
Properties of Galaxies and Groups: Nature versus NurtureSep 08 2011Due to the inherently nonlinear nature of gravity cosmological N-body simulations have become an invaluable tool when the growth of structure is being studied and modelled closer to the present epoch. Large simulations with high dynamical range have made ... More
On relation between discrete Frenet frames and the bi-Hamiltonian structure of the discrete nonlinear Schrödinger equationJan 13 2017The discrete Frenet equation entails a local framing of a discrete, piecewise linear polygonal chain in terms of its bond and torsion angles. In particular, the tangent vector of a segment is akin the classical O(3) spin variable. Thus there is a relation ... More
On the number of periodic classical trajectories in a Hamiltonian dynamical systemFeb 08 1995Periodic classical trajectories are of fundamental importance both in classical and quantum physics. Here we develop path integral techniques to investigate such trajectories in an arbitrary, not necessarily energy conserving hamiltonian system. In particular, ... More
Are Glueballs Knotted Closed Strings?Dec 12 2003Glueballs have a natural interpretation as closed strings in Yang-Mills theory. Their stability requires that the string carries a nontrivial twist, or then it is knotted. Since a twist can be either left-handed or right-handed, this implies that the ... More
Equation of state dependence of directed flow in a microscopic transport modelNov 23 2016We study the sensitivities of the directed flow in Au+Au collisions on the equation of state (EoS), employing the transport theoretical model JAM. The EoS is modified by introducing a new collision term in order to control the pressure of a system by ... More
Latest predictions from the EbyE NLO EKRT modelJul 06 2018We present the latest results from the NLO pQCD + saturation + viscous hydrodynamics (EbyE NLO EKRT) model. The parameters in the EKRT saturation model are fixed by the charged hadron multiplicity in the 0-5 \% 2.76 TeV Pb+Pb collisions. The $\sqrt{s}$, ... More
Derivation of transient relativistic fluid dynamics from the Boltzmann equation for a multi-component systemDec 06 2012We derive the non-equilibrium single-particle momentum distribution function of a hadron resonance gas. We then study the effects that this newly derived expression can have in the freeze-out description of fluid-dynamical models of heavy ion collisions ... More
Yang-Mills, Complex Structures and Chern's Last TheoremJan 07 2005Jul 15 2005Recently Shiing-Shen Chern suggested that the six dimensional sphere $\mathbb{S}^6$ has no complex structure. Here we explore the relations between his arguments and Yang-Mills theories. In particular, we propose that Chern's approach is widely applicable ... More
Leapfrogging vortex rings in the Landau-Lifshitz equationFeb 25 2014Vortex rings are ubiquitous in fluids, with smoke rings being a familiar example. The interaction of multiple vortex rings produces complex dynamical behaviour, such as the leapfrogging motion first analysed by Helmholtz more than a century and a half ... More
Solitons and Physics of the Lysogenic to Lytic Transition in Enterobacteria Lambda PhageApr 12 2011The lambda phage is a paradigm temperate bacteriophage. Its lysogenic and lytic life cycles echo competition between the DNA binding CI and CRO proteins. Here we address the Physics of this transition in terms of an energy function that portrays the backbone ... More
Knots and Swelling in Protein FoldingJun 26 2009Proteins can sometimes be knotted, and for many reasons the study of knotted proteins is rapidly becoming very important. For example, it has been proposed that a knot increases the stability of a protein. Knots may also alter enzymatic activities and ... More
Can Renormalization Group Flow End in a Big Mess?Apr 21 2003Apr 22 2003The field theoretical renormalization group equations have many common features with the equations of dynamical systems. In particular, the manner how Callan-Symanzik equation ensures the independence of a theory from its subtraction point is reminiscent ... More
On the Arnold Conjecture and the Atiyah-Patodi-Singer Index TheoremAug 20 1999Aug 25 1999The Arnold conjecture yields a lower bound to the number of periodic classical trajectories in a Hamiltonian system. Here we count these trajectories with the help of a path integral, which we inspect using properties of the spectral flow of a Dirac operator ... More
Partially Dual variables in SU(2) Yang-Mills TheoryJul 09 1998We propose a reformulation of SU(2) Yang-Mills theory in terms of new variables. These variables are appropriate for describing the theory in its infrared limit, and indicate that it admits knotlike configurations as stable solitons. As a consequence ... More
Toroidal Confugurations As Stable SolitonsMay 22 1997Previously we have proposed that in certain relativistic quantum field theories knotlike configurations may appear as stable solitons. Here we present a detailed investigation of the simplest knotted soliton, the torus-shaped unknot.
Equivariance, BRST and SuperspaceMar 21 1994The structure of equivariant cohomology in non-abelian localization formulas and topological field theories is discussed. Equivariance is formulated in terms of a nilpotent BRST symmetry, and another nilpotent operator which restricts the BRST cohomology ... More
Cohomological Partition Functions for a Class of Bosonic TheoriesJun 08 1992We argue, that for a general class of nontrivial bosonic theories the path integral can be related to an equivariant generalization of conventional characteristic classes.
Assessing the impacts of time to detection distribution assumptions on detection probability estimationDec 01 2016May 19 2017Abundance estimates from animal point-count surveys require accurate estimates of detection probabilities. The standard model for estimating detection from removal-sampled point-count surveys assumes that organisms at a survey site are detected at a constant ... More
Zeroing in on the initial state -- tomography using bulk, jets and photonsJul 30 2014One of the unsolved problems in the current 'standard model' of heavy ion physics is the apparent rapid thermalization of QCD matter in the pre-equilibrium stage. While it is challenging to probe this mechanism directly, there are now several observables ... More
Temperature dependence of $η/s$: uncertainties from the equation of stateNov 05 2018We perform a global model-to-data comparison on Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV and Pb+Pb collisions at $2.76$ TeV and $5.02$ TeV, using a 2+1D hydrodynamics model with the EKRT initial state and a shear viscosity over entropy density ratio ... More
Constraining energy loss from high-$p_{\rm T}$ azimuthal asymmetriesFeb 20 2019The nuclear modification factor $R_{\rm AA}$ has been satisfactorily described by various jet quenching models. Nonetheless, all these formalisms, until very recently, underpredicted the high-$p_{\rm T}$ (> 10 GeV) elliptic flow $v_2$. We find that the ... More
Influence of the shear viscosity of the quark-gluon plasma on elliptic flow in ultrarelativistic heavy-ion collisionsJan 12 2011Jun 17 2011We investigate the influence of a temperature-dependent shear viscosity over entropy density ratio eta/s on the transverse momentum spectra and elliptic flow of hadrons in ultrarelativistic heavy-ion collisions. We find that the elliptic flow in sqrt(s_NN) ... More
An ultraweak formulation of the Kirchhoff-Love plate bending model and DPG approximationMay 20 2018We develop and analyze an ultraweak variational formulation for a variant of the Kirchhoff-Love plate bending model. Based on this formulation, we introduce a discretization of the discontinuous Petrov-Galerkin type with optimal test functions (DPG). ... More
Jet quenching as a probe of the initial stages in heavy-ion collisionsFeb 08 2019Jet quenching provides a very flexible variety of observables which are sensitive to different energy- and time-scales of the strongly interacting matter created in heavy-ion collisions. Exploiting this versatility would make jet quenching an excellent ... More
Transition from ideal to viscous Mach cones in BAMPSAug 05 2012We investigate in a microscopical transport model the evolution of conical structures originating from the supersonic projectile moving through the matter of ultrarelativistic particles. Using different scenarios for the interaction between projectile ... More
Effect of temperature-dependent eta/s on flow anisotropiesDec 17 2011We investigate the effects of a temperature-dependent shear viscosity over entropy density ratio eta/s on the flow anisotropy coefficients v_2 and v_4 in ultrarelativistic heavy-ion collisions at RHIC and LHC. We find that v_4 is more sensitive to the ... More
Extracting $\hat{q}$ in event-by-event hydrodynamics and the centrality/energy puzzleMay 03 2017In our analysis, we combine event-by-event hydrodynamics, within the EKRT formulation, with jet quenching -ASW Quenching Weights- to obtain high-$p_T$ $R_{\rm AA}$ for charged particles at RHIC and LHC energies for different centralities. By defining ... More
On Weak Lensing Shape NoiseSep 16 2015One of the most powerful techniques to study the dark sector of the Universe is weak gravitational lensing. In practice, to infer the reduced shear, weak lensing measures galaxy shapes, which are the consequence of both the intrinsic ellipticity of the ... More
Topological Indices of ProteinsMar 11 2019Protein molecules can be approximated by discrete polygonal chains of amino acids. Standard topological tools can be applied to the smoothening of the polygons to introduce a topological classification of proteins, for example, using the self-linking ... More
Spin-Charge Separation and the Pauli ElectronApr 21 2006Jul 03 2006The separation between the spin and the charge converts the quantum mechanical Pauli Hamiltonian into the Hamiltonian of the non-Abelian Georgi-Glashow model, notorious for its magnetic monopoles and confinement. The independent spin and charge fluctuations ... More
Glueballs, closed fluxtubes and eta(1440)Aug 24 2003Apr 01 2004The $eta_L(1410)$ component of the $\eta(1440)$ pseudoscalar has strong affinity for glue. But its mass is incompatible with lattice simulations that predict a much higher value for the $0^{-+}$ glueball. As a consequence it has been suggested that $\eta_L(1410)$ ... More
On phase diagram and the pseudogap state in a linear chiral homopolymer modelJan 21 2015Dec 23 2015The phase structure of a homopolymer chain is investigated in terms of a universal theoretical model, designed to describe the infrared limit of slow spatial variations. The effects of chirality are studied and compared with the influence of a short-range ... More
Embedding Brans-Dicke gravity into electroweak theorySep 05 2007Jun 27 2008We argue that a version of the four dimensional Brans-Dicke theory can be embedded in the standard flat spacetime electroweak theory. The embedding involves a change of variables that separates the isospin from the hypercharge in the electroweak theory. ... More
Aspects of Duality and Confining StringsAug 27 1999Sep 01 1999We inspect the excitation energy spectrum of a confining string in terms of solitons in an effective field theory model. The spectrum can be characterized by a spectral function, and twisting and bending of the string is manifested by the invariance of ... More
BRST extension of the Faddeev modelAug 17 2005Aug 22 2005The Faddeev model is a second class constrained system. Here we construct its nilpotent BRST operator and derive the ensuing manifestly BRST invariant Lagrangian. Our construction employs the structure of Stuckelberg fields in a nontrivial fashion.
Wave Front Sets of Reductive Lie Group Representations IIMar 25 2014In this paper it is shown that the wave front set of a direct integral of singular, irreducible representations of a real, reductive algebraic group is contained in the singular set. Combining this result with the results of the first paper in this series, ... More
Percolation on Strings and the Cover-up of the c=1 DisasterOct 20 1993Feb 28 1995We study percolation on the worldsheets of string theory for $c=0,1/2,1$ and $2$. For $c<1$ we find that critical exponents measured from simulations agree quite well with the theoretical values. For $c=1$ we show how log corrections determined from the ... More
Wave Front Sets of Reductive Lie Group Representations IIMar 25 2014May 12 2017In this paper it is shown that the wave front set of a direct integral of singular, irreducible representations of a real, reductive algebraic group is contained in the singular set. Combining this result with the results of the first paper in this series, ... More
Tempered Representations and Nilpotent OrbitsSep 19 2012May 04 2015Given a nilpotent orbit O of a real, reductive algebraic group, a necessary condition is given for the existence of a tempered representation pi such that O occurs in the wave front cycle of pi. The coefficients of the wave front cycle of a tempered representation ... More
Fourier Transforms of Nilpotent, Coadjoint Orbits for GL(n,R)Sep 18 2012The main result of this paper is an explicit formula for the Fourier transform of the canonical measure on a nilpotent coadjoint orbit for GL(n,R). This paper also includes some results on limit formulas for reductive Lie groups including new proofs of ... More
Analysis of two transmission eigenvalue problems with a coated boundary conditionApr 29 2019In this paper, we investigate two transmission eigenvalue problems associated with the scattering of a media with a coated boundary. In recent years, there has been a lot of interest in studying these eigenvalue problems. It can be shown that the eigenvalues ... More
Optimal angle of the holomorphic functional calculus for the classical Ornstein-Uhlenbeck operator on $L^p$Dec 20 2018We give a simple proof of the fact that the classical Ornstein-Uhlenbeck operator $L$ is R-sectorial of angle $arcsin|1-2/p|$ on $L^{p}(\mathbb{R}^{n},\exp(-|x|^2/2)dx)$ (for $1<p<\infty$). Applying the abstract holomorphic functional calculus theory ... More
Incorrigible RepresentationsNov 12 2018Dec 25 2018As a consequence of his numerical local Langlands correspondence for $GL(n)$, Henniart deduced the following theorem: If $F$ is a nonarchimedean local field and if $\pi$ is an irreducible admissible representation of $GL(n,F)$, then, after a finite sequence ... More
Relativistic Shock Waves and Mach Cones in Viscous Gluon MatterApr 26 2010To investigate the formation and the propagation of relativistic shock waves in viscous gluon matter we solve the relativistic Riemann problem using a microscopic parton cascade. We demonstrate the transition from ideal to viscous shock waves by varying ... More
Upper semicontinuity of the lamination hullSep 30 2016Let $K \subseteq \mathbb{R}^{2 \times 2}$ be a compact set, let $K^{rc}$ be its rank-one convex hull, and let $L(K)$ be its lamination convex hull. It is shown that the mapping $K \to \overline{L(K)}$ is not upper semicontinuous on the diagonal matrices ... More
Comparison of Attitude Estimation Techniques for Low-cost Unmanned Aerial VehiclesFeb 24 2016Attitude estimation for small, low-cost unmanned aerial vehicles is often achieved using a relatively simple complementary filter that combines onboard accelerometers, gyroscopes, and magnetometer sensing. This paper explores the limits of performance ... More
Classification of the monomial Cremona transformations of the planeJul 24 2014We classify all monomial planar Cremona maps by multidegree using recent methods developed by Aluffi. Following the main result, we prove several more properties of the set of these maps, and also extend the results to the more general `r.c. monomial' ... More
The local Langlands conjecture for GL(n) over a p-adic field, n < pNov 29 1996Let F be a p-adic field and n a positive integer. The local Langlands conjecture asserts the existence of a bijection between irreducible admissible representations of GL(n,F) and n-dimensional admissible representations of the Weil-Deligne group of F. ... More
Detecting inclusions with a generalized impedance condition from electrostatic data via samplingAug 10 2017May 28 2019In this paper, we derive a Sampling Method to solve the inverse shape problem of recovering an inclusion with a generalized impedance condition from electrostatic Cauchy data. The generalized impedance condition is a second-order differential operator ... More
Heat Kernels and CyclesMay 26 2005We use the heat kernel (on differential forms) on a compact Riemannian manifold to assign a real number to a k-tuple of cycles on the manifold satisfying certain conditions. If k is 2, this number is the ordinary topological linking number, an integer ... More
Monomial principalization in the singular settingOct 04 2013Apr 15 2014We generalize an algorithm by Goward for principalization of monomial ideals in nonsingular varieties to work on any scheme of finite type over a field. The normal crossings condition considered by Goward is weakened to the condition that components of ... More
Toss and Spin Juggling State GraphsMay 12 2014We review the state approach to toss juggling and extend the approach to spin juggling, a new concept. We give connections to current research on random juggling and describe a professional-level juggling performance that further demonstrates the state ... More
From neural PCA to deep unsupervised learningNov 28 2014Feb 02 2015A network supporting deep unsupervised learning is presented. The network is an autoencoder with lateral shortcut connections from the encoder to decoder at each level of the hierarchy. The lateral shortcut connections allow the higher levels of the hierarchy ... More
The Index Bundle for a Family of Dirac-Ramond OperatorsFeb 09 2012We study the index bundle of the Dirac-Ramond operator associated with a family $\pi: Z \to X$ of compact spin manifolds. We view this operator as the formal twisted Dirac operator $\dd \otimes \bigotimes_{n=1}^{\infty}S_{q^n}TM_{\C}$ so that its index ... More
A short proof of the thumbtack lemmaApr 17 2013We give a short proof of the main algebraic result of \cite{zilber2006covers}, also known as the `thumbtack lemma'.
Optimal angle of the holomorphic functional calculus for the classical Ornstein-Uhlenbeck operator on $L^p$Dec 20 2018Jun 05 2019We give a simple proof of the fact that the classical Ornstein-Uhlenbeck operator $L$ is R-sectorial of angle $arcsin|1-2/p|$ on $L^{p}(\mathbb{R}^{n},\exp(-|x|^2/2)dx)$ (for $1<p<\infty$). Applying the abstract holomorphic functional calculus theory ... More
The Magellanic Bridge: The Nearest Purely Tidal Stellar PopulationDec 04 2006We report on observations of the stellar populations in twelve fields spanning the region between the Magellanic Clouds, made with the Mosaic-II camera on the 4-meter telescope at the Cerro-Tololo Inter-American Observatory. The two main goals of the ... More
Categoricity and covering spacesDec 10 2014This thesis develops some of the basic model theory of covers of algebraic curves. In particular, an equivalence between the good model-theoretic behaviour of the modular j-function, and the openness of certain Galois representations in the Tate-modules ... More
Incorrigible RepresentationsNov 12 2018Jul 22 2019As a consequence of his numerical local Langlands correspondence for $GL(n)$, Henniart deduced the following theorem: If $F$ is a nonarchimedean local field and if $\pi$ is an irreducible admissible representation of $GL(n,F)$, then, after a finite sequence ... More
Algebraic proofs of some fundamental theorems in algebraic $K$-theoryNov 20 2013We present news proofs of the additivity, resolution and cofinality theorems for the algebraic $K$-theory of exact categories. These proofs are entirely algebraic, based on Grayson's presentation of higher algebraic $K$-groups via binary complexes.
Algorithms for Image Analysis and Combination of Pattern Classifiers with Application to Medical DiagnosisOct 18 2009Medical Informatics and the application of modern signal processing in the assistance of the diagnostic process in medical imaging is one of the more recent and active research areas today. This thesis addresses a variety of issues related to the general ... More
Detecting inclusions with a generalized impedance condition from electrostatic data via samplingAug 10 2017Oct 15 2018In this paper, we derive a Sampling Method to solve the inverse shape problem of recovering an inclusion with a generalized impedance condition from electrostatic Cauchy data. The generalized impedance condition is a second-order differential operator ... More
Categoricity of the two sorted j-functionApr 17 2013We show that a natural, two sorted $\cL_{\omega_1,\omega}$ theory involving the modular $j$-function is categorical in all uncountable cardinaities. It is also shown that a slight weakening of the adelic Mumford-Tate conjecture for products of elliptic ... More
Testing rationality of coherent cohomology of Shimura varietiesDec 09 2012Let $G' \subset G$ be an inclusion of reductive groups whose real points have a non-trivial discrete series. Combining ergodic methods of Burger-Sarnak and the author with a positivity argument due to Li and the classification of minimal $K$-types of ... More
On the local Langlands correspondenceApr 22 2003The local Langlands correspondence for GL(n) of a non-Archimedean local field $F$ parametrizes irreducible admissible representations of $GL(n,F)$ in terms of representations of the Weil-Deligne group $WD_F$ of $F$. The correspondence, whose existence ... More
Orthonormal Compactly Supported Wavelets with Optimal Sobolev RegularityJul 16 1998Numerical optimization is used to construct new orthonormal compactly supported wavelets with Sobolev regularity exponent as high as possible among those mother wavelets with a fixed support length and a fixed number of vanishing moments. The increased ... More
The kernel of the monodromy of the universal family of degree $d$ smooth plane curvesApr 23 2019We consider the parameter space $\mathcal U_d$ of smooth plane curves of degree $d$. The universal smooth plane curve of degree $d$ is a fiber bundle $\cal E_d\to\cal U_d$ with fiber diffeomorphic to a surface $\Sigma_g$. This bundle gives rise to a monodromy ... More
On real growth and run-off companies in insurance ruin theoryNov 05 2015We study solvency of insurers in a comprehensive model where various economic factors affect the capital developments of the companies. The main interest is in the impact of real growth to ruin probabilities. The volume of the business is allowed to increase ... More
On a linearized p-Laplace equation with rapidly oscillating coefficientsJun 15 2015Nov 19 2015Related to a conjecture of Tom Wolff, we solve a singular Neumann problem for a linearized p-Laplace equation in the unit disk.
Computing Segre classes in arbitrary projective varietiesNov 21 2015Nov 26 2015We give an algorithm for computing Segre classes of subschemes of arbitrary projective varieties by computing degrees of a sequence of linear projections. Based on the fact that Segre classes of projective varieties commute with intersections by general ... More
Determination of the Shear Viscosity Relaxation Time at Weak and Strong CouplingAug 31 2011We investigate the microscopic origin of the relaxation time coefficient in relativistic fluid dynamics. We show that the extraction of the shear viscosity relaxation time via the gradient expansion is ambiguous and in general fails to give the correct ... More
Solution X-ray scattering (S/WAXS) and structure formation in protein dynamicsNov 24 2016We propose to develop mean field theory in combination with Glauber algorithm, to model and interpret protein dynamics and structure formation in small to wide angle x-ray scattering (S/WAXS) experiments. We develop the methodology by analysing the Engrailed ... More
Will Sanders Supporters Jump Ship for Trump? Fine-grained Analysis of Twitter FollowersMay 31 2016In this paper, we study the likelihood of Bernie Sanders supporters voting for Donald Trump instead of Hillary Clinton. Building from a unique time-series dataset of the three candidates' Twitter followers, which we make public here, we first study the ... More
To Follow or Not to Follow: Analyzing the Growth Patterns of the Trumpists on TwitterMar 27 2016In this paper, we analyze the growth patterns of Donald Trump's followers (Trumpists, henceforth) on Twitter. We first construct a random walk model with a time trend to study the growth trend and the effects of public debates. We then analyze the relationship ... More
Formation, Evolution and Properties of Isolated Field Elliptical GalaxiesFeb 03 2010[Abridged] We study the properties, evolution and formation mechanisms of isolated field elliptical galaxies. We create a mock catalogue of isolated field elliptical galaxies from the Millennium Simulation Galaxy Catalogue, and trace their merging histories. ... More
Are the nearby groups of galaxies gravitationally bound objects?Sep 20 2007We have compared numerical simulations to observations for the nearby (< 40 Mpc) groups of galaxies (Huchra & Geller 1982 and Ramella et al. 2002). The group identification is carried out using a group-finding algorithm developed by Huchra and Geller ... More
Predictions for 5.023 TeV Pb+Pb collisions at the LHCNov 13 2015We compute predictions for various low-transverse-momentum bulk observables in $\sqrt{s_{NN}} = 5.023$ TeV Pb+Pb collisions at the LHC from the event-by-event next-to-leading-order perturbative-QCD + saturation + viscous hydrodynamics ("EKRT") model. ... More
Pinning down QCD-matter shear viscosity in A+A collisions via EbyE fluctuations using pQCD + saturation + hydrodynamicsDec 16 2015We compute the initial energy densities produced in ultrarelativistic heavy-ion collisions from NLO perturbative QCD using a saturation conjecture to control soft particle production, and describe the subsequent space-time evolution of the system with ... More
Massively parallel approximate Gaussian process regressionOct 18 2013Jun 04 2014We explore how the big-three computing paradigms -- symmetric multi-processor (SMC), graphical processing units (GPUs), and cluster computing -- can together be brought to bare on large-data Gaussian processes (GP) regression problems via a careful implementation ... More
Origin of the Relaxation Time in Dissipative Fluid DynamicsFeb 23 2011May 01 2011We show how the linearized equations of motion of any dissipative current are determined by the analytical structure of the associated retarded Green's function. If the singularity of the Green's function, which is nearest to the origin in the complex-frequency ... More
Twisted Vortices in a Gauge Field TheoryJun 13 2001Nov 08 2001We inspect a particular gauge field theory model that describes the properties of a variety of physical systems, including a charge neutral two-component plasma, a Gross-Pitaevskii functional of two charged Cooper pair condensates, and a limiting case ... More
Automatically Stable Discontinuous Petrov-Galerkin Methods for Stationary Transport Problems: Quasi-Optimal Test Space NormJan 09 2012We investigate the application of the discontinuous Petrov-Galerkin (DPG) finite element framework to stationary convection-diffusion problems. In particular, we demonstrate how the quasi-optimal test space norm can be utilized to improve the robustness ... More
Catching Fire via "Likes": Inferring Topic Preferences of Trump Followers on TwitterMar 09 2016In this paper, we propose a framework to infer the topic preferences of Donald Trump's followers on Twitter. We first use latent Dirichlet allocation (LDA) to derive the weighted mixture of topics for each Trump tweet. Then we use negative binomial regression ... More
Dark Matter Halos in Galaxies and Globular Cluster Populations. II: Metallicity and MorphologyApr 13 2015An increasing body of data reveals a one-to-one linear correlation between galaxy halo mass and the total mass in its globular cluster (GC) population, M_{GCS} ~ M_h^{1.03 \pm 0.03}, valid over 5 orders of magnitude. We explore the nature of this correlation ... More
On-off Threshold Models of Social ContagionSep 10 2012We study binary state contagion dynamics on a social network where nodes act in response to the average state of their neighborhood. We model the competing tendencies of imitation and non-conformity by incorporating an off-threshold into standard threshold ... More
Lopsidependency in the Moser-Tardos framework: Beyond the Lopsided Lovasz Local LemmaOct 07 2016The Lopsided Lov\'{a}sz Local Lemma (LLLL) is a powerful probabilistic principle which has been used in a variety of combinatorial constructions. While originally a general statement about probability spaces, it has recently been transformed into a variety ... More
Light Hadron Spectroscopy and CharmoniumOct 17 2008During the last few years there has been a renaissance in charm and charmonium spectroscopy with higher precision measurements at the $\psi^{'}$ and $\psi(3770)$ coming from BESII and CLEOc and many new discoveries coming from B-factories. In this paper, ... More