Results for "Hannah Calcutt"

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The ALMA-PILS survey: The sulphur connection between protostars and comets: IRAS 16293-2422 B and 67P/Churyumov-GerasimenkoFeb 08 2018The evolutionary past of our Solar System can be pieced together by comparing analogous low-mass protostars with remnants of our Protosolar Nebula - comets. Sulphur-bearing molecules may be unique tracers of the joint evolution of the volatile and refractory ... More
A high resolution study of complex organic molecules in hot coresJul 07 2014We present the results of a line identification analysis using data from the IRAM Plateau de Bure Inferferometer, focusing on six massive star-forming hot cores: G31.41+0.31, G29.96-0.02, G19.61-0.23, G10.62-0.38, G24.78+0.08A1 and G24.78+0.08A2. We identify ... More
Asymptotic triangulations and Coxeter transformations of the annulusAug 03 2015Oct 06 2015Asymptotic triangulations can be viewed as limits of triangulations under the action of the mapping class group. In the case of the annulus, such triangulations have been introduced by Baur and Dupont. We construct an alternative method of obtaining these ... More
Event-by-Event Observables and FluctuationsNov 23 2012In this talk the status and open questions of the phenomenological description of all the stages of a heavy ion reaction are highlighted. Special emphasis is put on event-by-event fluctuations and associated observables. The first part is concentrated ... More
Identified Particle Spectra and Anisotropic Flow in an Event-by-Event Hybrid Approach in Pb+Pb collisions at $\sqrt{s_{\rm NN}}=2.76$ TeVMay 09 2011The first results from heavy ion collisions at the Large Hadron Collider for charged particle spectra and elliptic flow are compared to an event-by-event hybrid approach with an ideal hydrodynamic expansion. This approach has been shown to successfully ... More
Using simplicial volume to count maximally broken Morse trajectoriesJun 15 2015Given a closed Riemannian manifold of dimension $n$ and a Morse-Smale function, there are finitely many $n$-part broken trajectories of the negative gradient flow. We show that if the manifold admits a hyperbolic metric, then the number of $n$-part broken ... More
Local helioseismology and the active SunMay 14 2010The goal of local helioseismology is to elicit three-dimensional information about the sub-surface (or far-side) structure and dynamics of the Sun from observations of the helioseismic wave field at the surface. The physical quantities of interest include ... More
On the shape of subword complexity sequences of finite wordsSep 13 2013Sep 13 2014The subword complexity of a word $w$ over a finite alphabet $\mathcal{A}$ is a function that assigns for each positive integer $n$, the number of distinct subwords of length $n$ in $w$. The subword complexity of a word is a good measure of the randomness ... More
Some halting problems for abelian sandpiles are undecidable in dimension threeAug 01 2015The abelian sandpile model is a simple combinatorial model for critical behaviour which has the "abelian property" that the order in which we make moves does not change the final outcome of the game. This might seem to restrict the model's computational ... More
Anisotropic flow in transport+hydrodynamics hybrid approachesApr 07 2014Nov 26 2014This contribution to the focus issue covers anisotropic flow in hybrid approaches. The historical development of hybrid approaches and their impact on the interpretation of flow measurements is reviewed. The major ingredients of a hybrid approach and ... More
Semidualizing DG Modules over Tensor ProductsNov 25 2014We study the existence of nontrivial semidualizing DG modules over tensor products of DG algebras over a field. In particular, this gives a lower bound on the number of semidualizing DG modules over the tensor product.
Coefficients of McKay-Thompson series and distributions of the moonshine moduleAug 15 2015Jan 03 2016In a recent paper, Duncan, Griffin and Ono provide exact formulas for the coefficients of McKay-Thompson series and use them to find asymptotic expressions for the distribution of irreducible representations in the moonshine module $V^\natural = \bigoplus_n ... More
Restricting cohomology classes to disk and segment configuration spacesAug 23 2016The configuration space of n labeled disks of radius r inside the unit disk is denoted Conf_{n, r}(D^2). We study how the cohomology of this space depends on r. In particular, given a cohomology class of Conf_{n, 0}(D^2), for which r does its restriction ... More
Sequential recombination algorithm for jet clustering and background subtractionApr 03 2013Aug 14 2013We investigate a new sequential recombination algorithm which effectively subtracts background as it reconstructs the jet. We examine the new algorithm's behavior in light of existing algorithms, and we find that in Monte Carlo comparisons, the new algorithm's ... More
Stochastic Modelling of T-Cell-ActivationApr 13 2013We investigate a special part of the human immune system, namely the activation of T-Cells, using stochastic tools, especially sharp large deviation results. T-Cells have to distinguish reliably between foreign and self peptides which are both presented ... More
A family of maps with many small fibersFeb 12 2014Apr 03 2014The waist inequality states that for a continuous map from S^n to R^q, not all fibers can have small (n-q)-dimensional volume. We construct maps for which most fibers have small (n-q)-dimensional volume and all fibers have bounded (n-q)-dimensional volume. ... More
The numbers of tropical plane curves through points in general positionApr 19 2005Jan 10 2006We show that the number of tropical curves of given genus and degree through some given general points in the plane does not depend on the position of the points. In the case when the degree of the curves contains only primitive integral vectors this ... More
Eccentricity fluctuations in an integrated hybrid approach: Influence on elliptic flowFeb 04 2010May 04 2010The effects of initial state fluctuations on elliptic flow are investigated within a (3+1)d Boltzmann + hydrodynamics transport approach. The spatial eccentricity ($\epsilon_{\rm RP}$ and $\epsilon_{\rm part}$) is calculated for initial conditions generated ... More
Ideal hydrodynamics and elliptic flow at SPS energies: Importance of the initial conditionsJan 26 2009The elliptic flow excitation function calculated in a full (3+1)d hybrid Boltzmann approach with an intermediate hydrodynamic stage for heavy ion reactions from GSI-SIS to the highest CERN-SPS energies is discussed in the context of the experimental data. ... More
Particlization in hybrid modelsJun 15 2012Sep 20 2012In hybrid models, which combine hydrodynamical and transport approaches to describe different stages of heavy-ion collisions, conversion of fluid to individual particles, particlization, is a non-trivial technical problem. We describe in detail how to ... More
Congruence properties of Taylor coefficients of modular formsJun 11 2014In their work, Serre and Swinnerton-Dyer study the congruence properties of the Fourier coefficients of modular forms. We examine similar congruence properties, but for the coefficients of a modified Taylor expansion about a CM point $\tau$. These coefficients ... More
Sieved Enumeration of Interval Orders and Other Fishburn StructuresFeb 18 2015Mar 10 2015Following a result of Eriksen and Sj\"{o}strand (2014) we detail a technique to construct structures following the Fishburn distribution from appropriate Mahonian structures. This technique is introduced on a bivincular pattern of Bousquet-M\'elou et ... More
Consensus on Moving Neighborhood Model of Peterson GraphMar 08 2012In this paper, we study the consensus problem of multiple agents on a kind of famous graph, Peterson graph. It is an undirected graph with 10 vertices and 15 edges. Each agent randomly walks on this graph and communicates with each other if and only if ... More
Tropical descendant Gromov-Witten invariantsSep 08 2008Nov 29 2009We define tropical Psi-classes on the moduli space of rational tropical curves in R^2 and consider intersection products of Psi-classes and pull-backs of evaluations on this space. We show a certain WDVV equation which is sufficient to prove that tropical ... More
Deformation of tropical Hirzebruch surfaces and enumerative geometryMar 06 2013Sep 05 2014We illustrate the use of tropical methods by generalizing a formula due to Abramovich and Bertram, extended later by Vakil. Namely, we exhibit relations between enumerative invariants of the Hirzebruch surfaces $\Sigma_n$ and $\Sigma_{n+2}$, obtained ... More
The space of tropically collinear points is shellableNov 06 2007Jul 13 2009The space T_{d,n} of n tropically collinear points in a fixed tropical projective space TP^{d-1} is equivalent to the tropicalization of the determinantal variety of matrices of rank at most 2, which consists of real d x n matrices of tropical or Kapranov ... More
Traces of singular values of HauptmodulnJul 16 2014Sep 01 2014In an important paper, Zagier proved that certain half-integral weight modular forms are generating functions for traces of polynomials in the $j$-function. It turns out that Zagier's work makes it possible to algorithmically compute Hilbert class polynomials ... More
Kontsevich's formula and the WDVV equations in tropical geometrySep 27 2005Sep 09 2008Using Gromov-Witten theory the numbers of complex plane rational curves of degree d through 3d-1 general given points can be computed recursively with Kontsevich's formula that follows from the so-called WDVV equations. In this paper we establish the ... More
Effective N-particle collisions in a hadronic transport approachSep 05 2016Hadronic transport approaches based on an effective solution of the relativistic Boltzmann equation are widely applied for the dynamical description of heavy ion reactions at low beam energies. At high densities, the assumption of binary interactions ... More
Evolution of elliptic and triangular flow as a function of beam energy in a hybrid modelOct 29 2013Elliptic flow has been one of the key observables for establishing the finding of the quark-gluon plasma (QGP) at the highest energies of Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC). As a sign of collectively behaving matter, ... More
Sky subtraction at the Poisson limit with fibre-optic multi-object spectroscopyJul 05 2010We report on the limitations of sky subtraction accuracy for long duration fibre-optic multi-object spectroscopy of faint astronomical sources during long duration exposures. We show that while standard sky subtraction techniques yield accuracies consistent ... More
Tropical covers of curves and their moduli spacesMar 26 2013We define the tropical moduli space of covers of a tropical line in the plane as weighted abstract polyhedral complex, and the tropical branch map recording the images of the simple ramifications. Our main result is the invariance of the degree of the ... More
Tropical enumerative invariants of F_0 and F_2Aug 26 2008Jun 20 2011There is an equation relating numbers of curves on F_0 satisfying incidence conditions and numbers of curves on F_2 satisfying incidence conditions. The purpose of this paper is to give a tropical proof of this equation in the case of rational curves. ... More
Tremaine-Weinberg integrals for gas flows in double barsJan 09 2008We report on our attempts to achieve a nearly steady-state gas flow in hydrodynamical simulations of doubly barred galaxies. After exploring the parameter space, we construct two models, for which we evaluate the photometric and the kinematic integrals, ... More
On Unbounded Delays in Asynchronous Parallel Fixed-Point AlgorithmsSep 15 2016The need for scalable numerical solutions has motivated the development of asynchronous parallel algorithms, where a set of nodes run in parallel with little or no synchronization, thus computing with delayed information. This paper studies the convergence ... More
Initial State Fluctuations and Final State Correlations in Relativistic Heavy-Ion CollisionsDec 19 2013Jun 02 2014We review the phenomenology and theory of bulk observables in ultra-relativistic heavy-ion collisions, focussing on recent developments involving event-by-event fluctuations in the initial stages of a heavy ion collision, and how they manifest in observed ... More
On the Possibility of Event Shape Selection in Relativistic Heavy Ion CollisionsMay 13 2013Nov 12 2013We investigate the possibility of selecting heavy ion collision events with certain features in the initial state ("event engineering"). Anisotropic flow measurements in heavy ion reactions have confirmed the almost ideal fluid dynamical behaviour of ... More
A conditional strong large deviation result and a functional central limit theorem for the rate functionNov 21 2014Dec 04 2014We study the large deviation behaviour of $S_n=\sum_{j=1}^n W_jZ_j$, where $(W_j)_{j \in \mathbb N}$ and $(Z_j)_{j \in \mathbb N}$ are sequences of real-valued, independent and identically distributed random variables satisfying certain moment conditions, ... More
Automorphism groups of compact complex supermanifoldsJun 03 2015Let $\mathcal M$ be a compact complex supermanifold. We prove that the set $\mathrm{Aut}_{\bar 0}(\mathcal M)$ of automorphisms of $\mathcal M$ can be endowed with the structure of a complex Lie group acting holomorphically on $\mathcal M$, so that its ... More
Ensemble Methods for Convex Regression with Applications to Geometric Programming Based Circuit DesignJun 18 2012Convex regression is a promising area for bridging statistical estimation and deterministic convex optimization. New piecewise linear convex regression methods are fast and scalable, but can have instability when used to approximate constraints or objective ... More
Counting tropical elliptic plane curves with fixed j-invariantAug 18 2006Dec 17 2009In complex algebraic geometry, the problem of enumerating plane elliptic curves of given degree with fixed complex structure has been solved by R.Pandharipande using Gromov-Witten theory. In this article we treat the tropical analogue of this problem, ... More
Maximising $H$-Colourings of GraphsNov 09 2016For graphs $G$ and $H$, an $H$-colouring of $G$ is a map $\psi:V(G)\rightarrow V(H)$ such that $ij\in E(G)\Rightarrow\psi(i)\psi(j)\in E(H)$. The number of $H$-colourings of $G$ is denoted by $\hom(G,H)$. We prove the following: for all graphs $H$ and ... More
Evolution of elliptic and triangular flow as a function of collision energy in a hybrid modelOct 07 2013Apr 10 2014We study the collision energy dependence of elliptic flow v_2 and triangular flow v_3 in Au+Au collisions within the energy range sqrt(s_{NN}) = 5-200 GeV, utilizing a transport + hydrodynamics hybrid model. The transport part is described by the Ultrarelativistic ... More
Using simplicial volume to count multi-tangent trajectories of traversing vector fieldsMar 09 2015For a non-vanishing gradient-like vector field on a compact manifold $X^{n+1}$ with boundary, a discrete set of trajectories may be tangent to the boundary with reduced multiplicity $n$, which is the maximum possible. (Among them are trajectories that ... More
Length 3 Edge-Disjoint Paths and Partial OrientationJan 31 2012In 2003, it was claimed that the following problem was solvable in polynomial time: do there exist k edge-disjoint paths of length exactly 3 between vertices s and t in a given graph? The proof was flawed, and we show that this problem is NP-hard even ... More
Intersecting Psi-classes on tropical M_{0,n}Sep 25 2007Jul 01 2009We apply the tropical intersection theory developed by L. Allermann and J. Rau to compute intersection products of tropical Psi-classes on the moduli space of rational tropical curves. We show that in the case of zero-dimensional (stable) intersections, ... More
HELAS Local Helioseismology ActivitiesOct 19 2008The main goals of the HELAS local helioseismology network activity are to consolidate this field of research in Europe, to organise scientific workshops, and to facilitate the distribution of observations and data analysis software. Most of this is currently ... More
A Diagnostic for Localizing Red Giant Differential RotationAug 05 2016We present a simple diagnostic that can be used to constrain the location of the differential rotation in red giants with measured mixed mode rotational splittings. Specifically, in red giants with radii $\sim 4R_\odot$, the splittings of p-dominated ... More
The Caporaso-Harris formula and plane relative Gromov-Witten invariants in tropical geometryApr 19 2005Aug 01 2007Some years ago Caporaso and Harris have found a nice way to compute the numbers N(d,g) of complex plane curves of degree d and genus g through 3d+g-1 general points with the help of relative Gromov-Witten invariants. Recently, Mikhalkin has found a way ... More
Deviations of the Energy-Momentum Tensor from Equilibrium in the Initial State for Hydrodynamics from Transport ApproachesAug 18 2015Many hybrid models of heavy ion collisions construct the initial state for hydrodynamics from transport models. Hydrodynamics requires that the energy-momentum tensor $T^{\mu\nu}$ and four-currents $j^{\mu}$ do not deviate considerably from the equilibrium ... More
Collision Energy Evolution of Elliptic and Triangular Flow in a Hybrid ModelJun 01 2013While the existence of a strongly interacting state of matter, known as 'quark-gluon plasma' (QGP), has been established in heavy ion collision experiments in the past decade, the task remains to map out the transition from the hadronic matter to the ... More
Tropical Real Hurwitz numbersDec 13 2014Aug 25 2015In this paper, we define tropical analogues of real Hurwitz numbers, i.e. numbers of covers of surfaces with compatible involutions satisfying prescribed ramification properties. We prove a correspondence theorem stating the equality of the tropical numbers ... More
Decomposing labeled interval orders as pairs of permutationsMay 10 2014Oct 21 2014We introduce ballot matrices, a signed combinatorial structure whose definition naturally follows from the generating function for labeled interval orders. A sign reversing involution on ballot matrices is defined. We show that matrices fixed under this ... More
How to repair tropicalizations of plane curves using modificationsSep 25 2014Tropical geometry is sensitive to embeddings of algebraic varieties inside toric varieties. The purpose of this paper is to advertise tropical modifications as a tool to locally repair bad embeddings of plane curves, allowing the re-embedded tropical ... More
Experimental Estimation of Number of Clusters Based on Cluster QualityMar 10 2015Text Clustering is a text mining technique which divides the given set of text documents into significant clusters. It is used for organizing a huge number of text documents into a well-organized form. In the majority of the clustering algorithms, the ... More
Obtaining Laws of Thermodynamics for Ideal Gases using Elastic CollisionsMay 29 2013The purpose of this note is to see to what extent ideal gas laws can be obtained from simple Newtonian mechanics, specifically elastic collisions. We present simple one-dimensional situations that seem to validate the laws. The first section describes ... More
Reconstruction from $k$-decks for graphs with maximum degree 2Sep 01 2016The $k$-deck of a graph is its multiset of induced subgraphs on $k$ vertices. We prove that $n$-vertex graphs with maximum degree $2$ have the same $k$-decks if each cycle has at least $k+1$ vertices, each path component has at least $k-1$ vertices, and ... More
The Pulsation Period of the Hot Hydrogen-Deficient Star MV SgrFeb 27 2012MV Sgr is a hot, hydrogen-deficient star which has undergone R CrB fadings. We have used self-correlation analysis and Fourier analysis of CCD V photometry in the AAVSO International Database to identify a period of 8.0 days in this star; the amplitude ... More
The Influence of Social Movements on Space Astronomy PolicyAug 21 2014Aug 22 2014Public engagement (PE) initiatives can lead to a long term public support of science. However most of the real impact of PE initiatives within the context of long-term science policy is not completely understood. An examination of the National Aeronautics ... More
Flaring Solar Hale Sector BoundariesOct 13 2010Oct 15 2010Magnetic fields and the occurrence of flares and microflares are strongly concentrated near that portion (the Hale boundary) in each solar hemisphere where the change in magnetic sector polarity is the same as that between leading and following sunspot ... More
First Structure Formation: A Simulation of Small Scale Structure at High RedshiftSep 15 2000We describe the results of a simulation of collisionless cold dark matter in a LambdaCDM universe to examine the properties of objects collapsing at high redshift (z=10). We analyze the halos that form at these early times in this simulation and find ... More
Generating Music from LiteratureMar 10 2014We present a system, TransProse, that automatically generates musical pieces from text. TransProse uses known relations between elements of music such as tempo and scale, and the emotions they evoke. Further, it uses a novel mechanism to determine sequences ... More
On the ranks of elliptic curves with isogeniesNov 04 2016In recent years, the question of whether the ranks of elliptic curves defined over $\mathbb{Q}$ are unbounded has garnered much attention. One can create refined versions of this question by restricting one's attention to elliptic curves over $\mathbb{Q}$ ... More
The subset-matched Jaccard index for evaluation of Segmentation for Plant ImagesNov 21 2016We describe a new measure for the evaluation of region level segmentation of objects, as applied to evaluating the accuracy of leaf-level segmentation of plant images. The proposed approach enforces the rule that a region (e.g. a leaf) in either the image ... More
Tropical compactification and the Gromov--Witten theory of $\mathbb{P}^1$Oct 10 2014Aug 23 2016We use tropical and nonarchimedean geometry to study the moduli space of genus $0$ stable maps to $\mathbb{P}^1$ relative to two points. This space is exhibited as a tropical compactification in a toric variety. Moreover, the fan of this toric variety ... More
Universal features of dynamic heterogeneity in supercooled liquidsOct 03 2013A few years ago it was showed that some systems that have very similar local structure, as quantified by the pair correlation function, exhibit vastly different slowing down upon supercooling [L. Berthier and G. Tarjus, Phys. Rev. Lett. 103, 170601 (2009); ... More
Radiative Transfer Models of a Possible Planet in the AB Aurigae DiskMar 20 2010Recent coronagraphic imaging of the AB Aurigae disk has revealed a region of low polarized scattered light suggestive of perturbations from a planet at a radius of ~100 AU. We model this darkened region using our fully non-plane-parallel radiative-transfer ... More
The spectral difference between solar flare HXR coronal and footpoint sources due to wave-particle interactionsMar 11 2011Investigate the spatial and spectral evolution of hard X-ray (HXR) emission from flare accelerated electron beams subject to collisional transport and wave-particle interactions in the solar atmosphere. We numerically follow the propagation of a power-law ... More
Transmission spectral properties of clouds for hot Jupiter exoplanetsSep 26 2014Sep 30 2014Clouds have an important role in the atmospheres of planetary bodies. It is expected that, like all the planetary bodies in our solar system, exoplanet atmospheres will also have substantial cloud coverage, and evidence is mounting for clouds in a number ... More
Signatures of Planet Formation in Gravitationally Unstable DisksMar 07 2007In this paper, we calculate simulated scattered light images of a circumstellar disk in which a planet is forming by gravitational instability. The simulated images bear no correlation to the vertically integrated surface density of the disk, but rather ... More
Understanding the meaning of Greek temples' orientations. Akragas Valley of the Temples as a case studyNov 08 2015The issue of the orientation of Greek Temples has been the subject of several debates since the end of the 19 century. In fact, although a general tendency to orientation within the arc of the rising sun is undeniable, specific patterns and true meaning ... More
Sublimation of the Endohedral Fullerene Er3N@C80Dec 18 2009Sep 16 2010The heat of sublimation of the endohedral metallofullerene Er3N@C80 was measured via Knudsen effusion mass spectrometry. The large molecule consists of a C80 fullerene cage which is stabilized by comprising a complex of three erbium atoms bounded to a ... More
What the collective flow excitation function can tell about the quark-gluon plasmaAug 01 2014Recent STAR data from the RHIC beam energy scan (BES) show that the midrapidity slope dv1/dy of the directed flow v1 of net-protons changes sign twice within the collision energy range 7.7 - 39 GeV. To investigate this phenomenon, we study the collision ... More
Dilepton production with the SMASH modelApr 24 2016In this work the SMASH model is presented ("Simulating Many Accelerated Strongly-Interacting Hadrons"), a next-generation hadronic transport approach, which is designed to describe the non-equilibrium evolution of hadronic matter in heavy-ion collisions. ... More
Numerical Sets, Core Partitions, and Integer Points in PolytopesSep 21 2015We study a correspondence between numerical sets and integer partitions that leads to a bijection between simultaneous core partitions and the integer points of a certain polytope. We use this correspondence to prove combinatorial results about core partitions. ... More
Type I Migration in a Non-Isothermal Protoplanetary DiskOct 22 2004We calculate rates of Type I migration of protoplanets in a non-isothermal three-dimensional protoplanetary disk, building upon planet-disk models developed in previous work. We find that including the vertical thickness of the disk results in a decrease ... More
Bayesian nonparametric multivariate convex regressionSep 01 2011In many applications, such as economics, operations research and reinforcement learning, one often needs to estimate a multivariate regression function f subject to a convexity constraint. For example, in sequential decision processes the value of a state ... More
Multivariate convex regression with adaptive partitioningMay 10 2011Nov 13 2011We propose a new, nonparametric method for multivariate regression subject to convexity or concavity constraints on the response function. Convexity constraints are common in economics, statistics, operations research, financial engineering and optimization, ... More
Enhancing Heralding Efficiency and Biphoton Rate in Type-I Spontaneous Parametric Down-ConversionOct 03 2014The nonlinear optical process of spontaneous parametric down-conversion (SPDC) is widely studied for applications in quantum information science due to its ability to produce two photons that can be entangled in many degrees of freedom. For applications ... More
Granular discharge and clogging for tilted hoppersOct 02 2008May 26 2009We measure the flux of spherical glass beads through a hole as a systematic function of both tilt angle and hole diameter, for two different size beads. The discharge increases with hole diameter in accord with the Beverloo relation for both horizontal ... More
Multi-thermal dynamics and energetics of a coronal mass ejection in the low solar atmosphereDec 21 2012The aim of this work is to determine the multi-thermal characteristics and plasma energetics of an eruptive plasmoid and occulted flare observed by Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA). We study an event from 03-Nov-2010 (peaking ... More
The j-invariant of a plane tropical cubicSep 24 2007Several results in tropical geometry have related the j-invariant of an algebraic plane curve of genus one to the cycle length of a tropical curve of genus one. In this paper, we prove that for a plane cubic over the field of Puiseux series the negative ... More
Quantum Mechanics with a Momentum-Space Artificial Magnetic FieldMar 24 2014Nov 19 2014The Berry curvature is a geometrical property of an energy band which acts as a momentum space magnetic field in the effective Hamiltonian describing single-particle quantum dynamics. We show how this perspective may be exploited to study systems directly ... More
Momentum-space Harper-Hofstadter modelNov 05 2014Aug 14 2015We show how the weakly trapped Harper-Hofstadter model can be mapped onto a Harper-Hofstadter model in momentum space. In this momentum-space model, the band dispersion plays the role of the periodic potential, the Berry curvature plays the role of an ... More
Effects of Berry Curvature on the Collective Modes of Ultracold GasesJun 20 2013Nov 28 2013Topological energy bands have important geometrical properties described by the Berry curvature. We show that the Berry curvature changes the hydrodynamic equations of motion for a trapped Bose-Einstein condensate, and causes significant modifications ... More
An algorithm for lifting points in a tropical varietyMay 16 2007Jul 28 2009The aim of this paper is to give a constructive proof of one of the basic theorems of tropical geometry: given a point on a tropical variety (defined using initial ideals), there exists a Puiseux-valued ``lift'' of this point in the algebraic variety. ... More
Gaps in Protoplanetary Disks as Signatures of Planets: I. Methodology and ValidationFeb 15 2012We examine the observational consequences of partial gaps being opened by planets in protoplanetary disks. We model the disk using a static alpha-disk model with detailed radiative transfer, parametrizing the shape and size of the partially cleared gaps ... More
Enumeration of Complex and Real Surfaces via Tropical GeometryMar 30 2015Jul 20 2015We prove a correspondence theorem for singular tropical surfaces in real three space, which recovers singular algebraic surfaces in an appropriate toric three-fold that tropicalize to a given singular tropical surface. Furthermore, we develop a three-dimensional ... More
Nero's "solar" kingship and the architecture of Domus AureaDec 29 2013Dec 31 2013The Domus Aurea, Nero's last "palace" constructed in the very heart of ancient Rome, is a true masterpiece of Roman architecture. We explore here symbolic aspects of the emperor's project, analysing the archaeoastronomy of the best preserved part of the ... More
Failure mechanisms of graphene under tensionApr 11 2010Recent experiments established pure graphene as the strongest material known to mankind, further invigorating the question of how graphene fails. Using density functional theory, we reveal the mechanisms of mechanical failure of pure graphene under a ... More
Correlated fluctuations in strongly-coupled binary networks beyond equilibriumDec 03 2015Randomly coupled Ising spins constitute the classical model of collective phenomena in disordered systems, with applications covering ferromagnetism, combinatorial optimization, protein folding, stock market dynamics, and social dynamics. The phase diagram ... More
Polynomiality, Wall Crossings and Tropical Geometry of Rational Double Hurwitz CyclesSep 25 2012May 19 2013We study rational double Hurwitz cycles, i.e. loci of marked rational stable curves admitting a map to the projective line with assigned ramification profiles over two fixed branch points. Generalizing the phenomenon observed for double Hurwitz numbers, ... More
Time--distance inversions for horizontal and vertical flows on supergranular scales applied to MDI and HMI dataFeb 04 2013We study the possibility of consistent extension of MDI full-disc helioseismic campaigns with the growing data set of HMI observations. To do so, we down-sample and filter the HMI Dopplegrams so that the resulting spatial power spectrum is similar to ... More
Kinetic stability and energetics of simulated glasses created by constant pressure coolingAug 19 2016We use computer simulations to study the cooling rate dependence of the stability and energetics of model glasses created at constant pressure conditions and compare the results with glasses formed at constant volume conditions. To examine the stability, ... More
Gaps in Protoplanetary Disks as Signatures of Planets: II. Inclined DisksMay 27 2013We examine the observational appearance of partial gaps being opened by planets in protoplanetary disks, considering the effects of the inclination relative to the line of sight. The gap's trough is darkened by both shadowing and cooling, relative to ... More
Differential Emission Measures from the Regularized Inversion of Hinode and SDO dataJan 12 2012Jan 13 2012We develop and apply an enhanced regularization algorithm, used in RHESSI X-ray spectral analysis, to constrain the ill-posed inverse problem that is determining the DEM from solar observations. We demonstrate this computationally fast technique applied ... More
Tropical Hurwitz NumbersApr 03 2008Jul 16 2010Hurwitz numbers count genus g, degree d covers of the projective line with fixed branch locus. This equals the degree of a natural branch map defined on the Hurwitz space. In tropical geometry, algebraic curves are replaced by certain piece-wise linear ... More
Properties of Generalized Derangement GraphsJun 27 2011A permutation sigma in Sn is a k-derangement if for any subset X = {a1, . . ., ak} \subseteq [n], {sigma(a1), . . ., sigma(ak)} is not equal to X. One can form the k-derangement graph on the set of permutations of Sn by connecting two permutations sigma ... More
Connotation Frames: A Data-Driven InvestigationJun 09 2015Aug 22 2016Through a particular choice of a predicate (e.g., "x violated y"), a writer can subtly connote a range of implied sentiments and presupposed facts about the entities x and y: (1) writer's perspective: projecting x as an "antagonist"and y as a "victim", ... More