Results for "Adib Mehrabi"
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A Note on Approximating 2-TransmittersDec 05 2015A k-transmitter in a simple orthogonal polygon P is a mobile guard that travels back and forth along an orthogonal line segment s inside P. The k-transmitter can see a point p in P if there exists a point q on s such that the line segment pq is normal ... More Approximating Weighted Duo-Preservation in Comparative GenomicsAug 30 2017Motivated by comparative genomics, Chen et al. [9] introduced the Maximum Duo-preservation String Mapping (MDSM) problem in which we are given two strings $s_1$ and $s_2$ from the same alphabet and the goal is to find a mapping $\pi$ between them so as ... More Unique Set Cover on Unit Disks and Unit SquaresJul 25 2016We study the Unique Set Cover problem on unit disks and unit squares. For a given set $P$ of $n$ points and a set $D$ of $m$ geometric objects both in the plane, the objective of the Unique Set Cover problem is to select a subset $D'\subseteq D$ of objects ... More Does the Boltzmann principle need a dynamical correction?Apr 27 2002Jun 10 2004In an attempt to derive thermodynamics from classical mechanics, an approximate expression for the equilibrium temperature of a finite system has been derived [M. Bianucci, R. Mannella, B. J. West, and P. Grigolini, Phys. Rev. E 51, 3002 (1995)] which ... More NP-hardness of the cluster minimization problem revisitedSep 06 2005The computational complexity of the "cluster minimization problem" is revisited [L. T. Wille and J. Vennik, J. Phys. A 18, L419 (1985)]. It is argued that the original NP-hardness proof does not apply to pairwise potentials of physical interest, such ... More Algorithms for Brownian first passage time estimationApr 27 2009A class of algorithms in discrete space and continuous time for Brownian first passage time estimation is considered. A simple algorithm is derived that yields exact mean first passage times (MFPT) for linear potentials in one dimension, regardless of ... More Ergodicity and the Classical Lambda Phi^4 Lattice Field TheoryOct 15 2000In this talk we present some studies in the approach to equilibrium of the classical lambda phi^4 theory on the lattice, giving particular emphasis to its pedagogical usefulness in the context of classical statistical field theory (such as both the analytical ... More Random walk approach to the d-dimensional disordered Lorentz gasNov 12 2007Feb 15 2008A correlated random walk approach to diffusion is applied to the disordered nonoverlapping Lorentz gas. By invoking the Lu-Torquato theory for chord-length distributions in random media [J. Chem. Phys. 98, 6472 (1993)], an analytic expression for the ... More Adiabatic invariance with first integrals of motionMay 11 2002Oct 02 2002The construction of a microthermodynamic formalism for isolated systems based on the concept of adiabatic invariance is an old but seldom appreciated effort in the literature, dating back at least to P. Hertz [Ann. Phys. (Leipzig) 33, 225 (1910)]. An ... More On Guarding Orthogonal Polygons with Bounded TreewidthJun 07 2017There exist many variants of guarding an orthogonal polygon in an orthogonal fashion: sometimes a guard can see an entire rectangle, or along a staircase, or along an orthogonal path with at most $k$ bends. In this paper, we study all these guarding models ... More Constrained Orthogonal Segment StabbingApr 30 2019Let $S$ and $D$ each be a set of orthogonal line segments in the plane. A line segment $s\in S$ \emph{stabs} a line segment $s'\in D$ if $s\cap s'\neq\emptyset$. It is known that the problem of stabbing the line segments in $D$ with the minimum number ... More Studying wave optics in the light curve of exoplanet microlensingJul 17 2012Mar 13 2013We study the wave optics features of gravitational microlensing by a binary lens composed of a planet and a parent star. In this system, the source star near the caustic line produces a pair of images in which they can play the role of secondary sources ... More On $r$-Guarding Thin Orthogonal PolygonsApr 25 2016Guarding a polygon with few guards is an old and well-studied problem in computational geometry. Here we consider the following variant: We assume that the polygon is orthogonal and thin in some sense, and we consider a point $p$ to guard a point $q$ ... More Information gains from Monte Carlo Markov ChainsApr 26 2019In this paper, we present a novel method for computing the relative entropy as well as the expected relative entropy using an MCMC chain. The relative entropy from information theory can be used to quantify differences in posterior distributions of a ... More Kink Dynamics in a Topological Phi^4 LatticeApr 26 2001Jun 20 2001It was recently proposed a novel discretization for nonlinear Klein-Gordon field theories in which the resulting lattice preserves the topological (Bogomol'nyi) lower bound on the kink energy and, as a consequence, has no Peierls-Nabarro barrier even ... More Tachyon warm-intermediate inflation in the light of Planck dataApr 19 2016Sep 17 2016We study the main properties of the warm inflationary model based on Barrow's solution for the scale factor of the universe. Within this framework we calculate analytically the basic slow roll parameters for different versions of warm inflation. We test ... More How clustering dark energy affects matter perturbationsApr 06 2015Aug 01 2015The rate of structure formation in the Universe is different in homogeneous and clustered dark energy models. The degree of dark energy clustering depends on the magnitude of its effective sound speed $c^{2}_{\rm eff}$ and for $c_{\rm eff}=0$ dark energy ... More Gauge-QuintessenceOct 03 2015In this work, we introduce a new quintessence model associated with non-Abelian gauge fields, minimally coupled to Einstein gravity. This gauge theory has been originally introduced and studied as an inflationary model, called gauge-flation. Here, however, ... More Measuring the effects of Loop Quantum Cosmology in the CMB dataMay 16 2017In this Essay we investigate the observational signatures of Loop Quantum Cosmology (LQC) in the CMB data. First, we concentrate on the dynamics of LQC and we provide the basic cosmological functions. We then obtain the power spectrum of scalar and tensor ... More Sliding k-Transmitters: Hardness and ApproximationJul 25 2016A sliding k-transmitter in an orthogonal polygon P is a mobile guard that travels back and forth along an orthogonal line segment s inside P. It can see a point p in P if the perpendicular from p onto s intersects the boundary of P at most k times. We ... More Deep Learning Based Sphere DecodingJul 06 2018In this paper, a deep learning (DL)-based sphere decoding algorithm is proposed, where the radius of the decoding hypersphere is learnt by a deep neural network (DNN). The performance achieved by the proposed algorithm is very close to the optimal maximum ... More Long-lived oscillons from asymmetric bubblesMar 07 2002Sep 11 2002The possibility that extremely long-lived, time-dependent, and localized field configurations (``oscillons'') arise during the collapse of asymmetrical bubbles in 2+1 dimensional phi^4 models is investigated. It is found that oscillons can develop from ... More Constraints on shear and rotation with massive galaxy clustersAug 29 2016A precise determination of the mass function is an important tool to verify cosmological predictions of the $\Lambda$CDM model and to infer more precisely the better model describing the evolution of the Universe. Galaxy clusters have been currently used ... More Constraints on shear and rotation with massive galaxy clustersAug 29 2016Nov 14 2016A precise determination of the mass function is an important tool to verify cosmological predictions of the $\Lambda$CDM model and to infer more precisely the better model describing the evolution of the Universe. Galaxy clusters have been currently used ... More Generalized Ghost Dark Energy with Non-Linear InteractionNov 20 2016In this paper we investigate ghost dark energy model in the presence of non-linear interaction between dark energy and dark matter. The functional form of dark energy density in the generalized ghost dark energy (GGDE) model is $\rho_D\equiv f(H, H^2)$ ... More Agegraphic dark energy: growth index and cosmological implicationsAug 31 2016Sep 21 2016We study the main cosmological properties of the agegraphic dark energy model at the expansion and perturbation levels. Initially, using the latest cosmological data we implement a joint likelihood analysis in order to constrain the cosmological parameters. ... More On Unique Independence Weighted GraphsJul 01 2009An independent set in a graph G is a set of vertices no two of which are joined by an edge. A vertex-weighted graph associates a weight with every vertex in the graph. A vertex-weighted graph G is called a unique independence vertex-weighted graph if ... More Finding Pairwise Intersections Inside a Query RangeFeb 21 2015We study the following problem: preprocess a set O of objects into a data structure that allows us to efficiently report all pairs of objects from O that intersect inside an axis-aligned query range Q. We present data structures of size $O(n({\rm polylog} ... More 1-Bend RAC Drawings of 1-Planar GraphsAug 30 2016A graph is 1-planar if it has a drawing where each edge is crossed at most once. A drawing is RAC (Right Angle Crossing) if the edges cross only at right angles. The relationships between 1-planar graphs and RAC drawings have been partially studied in ... More Interferometry for rotating sourcesAug 17 2015Jan 06 2016The two particle interferometry method to determine the size of the emitting source after a heavy ion collision is extended. Following the extension of the method to spherical expansion dynamics, here we extend the method to rotating systems. It is shown ... More Drawing HV-Restricted Planar GraphsApr 14 2019A strict orthogonal drawing of a graph $G=(V, E)$ in $\mathbb{R}^2$ is a drawing of $G$ such that each vertex is mapped to a distinct point and each edge is mapped to a horizontal or vertical line segment. A graph $G$ is $HV$-restricted if each of its ... More Minimum Perimeter-Sum Partitions in the PlaneMar 16 2017Let $P$ be a set of $n$ points in the plane. We consider the problem of partitioning $P$ into two subsets $P_1$ and $P_2$ such that the sum of the perimeters of $\text{CH}(P_1)$ and $\text{CH}(P_2)$ is minimized, where $\text{CH}(P_i)$ denotes the convex ... More On the Minimum Consistent Subset ProblemOct 22 2018Nov 26 2018Let $P$ be a set of $n$ colored points in the plane. Introduced by Hart (1968), a consistent subset of $P$, is a set $S\subseteq P$ such that for every point $p$ in $P\setminus S$, the closest point of $p$ in $S$ has the same color as $p$. The consistent ... More Boundary Labeling for Rectangular DiagramsMar 28 2018Given a set of $n$ points (sites) inside a rectangle $R$ and $n$ points (label locations or ports) on its boundary, a boundary labeling problem seeks ways of connecting every site to a distinct port while achieving different labeling aesthetics. We examine ... More Constraints to dark energy using PADE parameterisationsJun 07 2017We put constraints on dark energy properties using the PADE parameterisation, and compare it to the same constraints using Chevalier-Polarski-Linder (CPL) and $\Lambda$CDM, at both the background and the perturbation levels. The dark energy equation of ... More DynamicGEM: A Library for Dynamic Graph Embedding MethodsNov 26 2018DynamicGEM is an open-source Python library for learning node representations of dynamic graphs. It consists of state-of-the-art algorithms for defining embeddings of nodes whose connections evolve over time. The library also contains the evaluation framework ... More On Guarding Orthogonal Polygons with Sliding CamerasApr 25 2016A sliding camera inside an orthogonal polygon $P$ is a point guard that travels back and forth along an orthogonal line segment $\gamma$ in $P$. The sliding camera $g$ can see a point $p$ in $P$ if the perpendicular from $p$ onto $\gamma$ is inside $P$. ... More Range-Clustering QueriesMay 17 2017In a geometric $k$-clustering problem the goal is to partition a set of points in $\mathbb{R}^d$ into $k$ subsets such that a certain cost function of the clustering is minimized. We present data structures for orthogonal range-clustering queries on a ... More Polygon Simplification by Minimizing Convex CornersDec 13 2018Let $P$ be a polygon with $r>0$ reflex vertices and possibly with holes and islands. A subsuming polygon of $P$ is a polygon $P'$ such that $P \subseteq P'$, each connected component $R$ of $P$ is a subset of a distinct connected component $R'$ of $P'$, ... More Approximability of Covering Cells with Line SegmentsSep 26 2018In COCOA 2015, Korman et al. studied the following geometric covering problem: given a set $S$ of $n$ line segments in the plane, find a minimum number of line segments such that every cell in the arrangement of the line segments is covered. Here, a line ... More Geodesic Obstacle Representation of GraphsMar 09 2018An obstacle representation of a graph is a mapping of the vertices onto points in the plane and a set of connected regions of the plane (called obstacles) such that the straight-line segment connecting the points corresponding to two vertices does not ... More Optimal Locally Repairable Codes with Improved Update ComplexityJun 30 2016Jul 14 2016For a systematic erasure code, update complexity (UC) is defined as the maximum number of parity blocks needed to be changed when some information blocks are updated. Locally repairable codes (LRCs) have been recently proposed and used in real-world distributed ... More Wireless THz link with optoelectronic transmitter and receiverJan 10 2019Photonics might play a key role in future wireless communication systems that operate at THz carrier frequencies. A prime example is the generation of THz data streams by mixing optical signals in high-speed photodetectors. Over the previous years, this ... More