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Articles 1 - 14 of 14
Full-Text Articles in Physical Sciences and Mathematics
Spherical Tropicalization, Anastasios Vogiannou
Spherical Tropicalization, Anastasios Vogiannou
Doctoral Dissertations
In this thesis, I extend tropicalization of subvarieties of algebraic tori over a trivially valued algebraically closed field to subvarieties of spherical homogeneous spaces. I show the existence of tropical compactifications in a general setting. Given a tropical compactification of a closed subvariety of a spherical homogeneous space, I show that the support of the colored fan of the ambient spherical variety agrees with the tropicalization of the closed subvariety. I provide examples of tropicalization of subvarieties of GL(n), SL(n), and PGL(n).
Skein Theory And Algebraic Geometry For The Two-Variable Kauffman Invariant Of Links, Thomas Shelly
Skein Theory And Algebraic Geometry For The Two-Variable Kauffman Invariant Of Links, Thomas Shelly
Doctoral Dissertations
We conjecture a relationship between the Hilbert schemes of points on a singular plane curve and the Kauffman invariant of the link associated to the singularity. Specifcally, we conjecture that the generating function of certain weighted Euler characteristics of the Hilbert schemes is given by a normalized specialization of the difference between the Kauffman and HOMFLY polynomials of the link. We prove the conjecture for torus knots. We also develop some skein theory for computing the Kauffman polynomial of links associated to singular points on plane curves.
Algebraicity Of Rational Hodge Isometries Of K3 Surfaces, Nikolay Buskin
Algebraicity Of Rational Hodge Isometries Of K3 Surfaces, Nikolay Buskin
Doctoral Dissertations
Consider any rational Hodge isometry $\psi:H^2(S_1,\QQ)\rightarrow H^2(S_2,\QQ)$ between any two K\"ahler $K3$ surfaces $S_1$ and $S_2$. We prove that the cohomology class of $\psi$ in $H^{2,2}(S_1\times S_2)$ is a polynomial in Chern classes of coherent analytic sheaves over $S_1 \times S_2$. Consequently, the cohomology class of $\psi$ is algebraic whenever $S_1$ and $S_2$ are algebraic.
Topology Of The Affine Springer Fiber In Type A, Tobias Wilson
Topology Of The Affine Springer Fiber In Type A, Tobias Wilson
Doctoral Dissertations
We develop algorithms for describing elements of the affine Springer fiber in type A for certain 2 g(C[[t]]). For these , which are equivalued, integral, and regular, it is known that the affine Springer fiber, X, has a paving by affines resulting from the intersection of Schubert cells with X. Our description of the elements of Xallow us to understand these affine spaces and write down explicit dimension formulae. We also explore some closure relations between the affine spaces and begin to describe the moment map for the both the regular and extended torus action.
Equivariant Intersection Cohomology Of Bxb Orbit Closures In The Wonderful Compactification Of A Group, Stephen Oloo
Equivariant Intersection Cohomology Of Bxb Orbit Closures In The Wonderful Compactification Of A Group, Stephen Oloo
Doctoral Dissertations
This thesis studies the topology of a particularly nice compactification that exists for semisimple adjoint algebraic groups: the wonderful compactification. The compactifica- tion is equivariant, extending the left and right action of the group on itself, and we focus on the local and global topology of the closures of Borel orbits. It is natural to study the topology of these orbit closures since the study of the topology of Borel orbit closures in the flag variety (that is, Schubert varieties) has proved to be inter- esting, linking geometry and representation theory since the local intersection cohomology Betti numbers turned out …
Discrete Solitons And Vortices In Anisotropic Hexagonal And Honeycomb Lattices, Q E. Hoq, Panayotis G. Kevrekidis, A R. Bishop
Discrete Solitons And Vortices In Anisotropic Hexagonal And Honeycomb Lattices, Q E. Hoq, Panayotis G. Kevrekidis, A R. Bishop
Mathematics and Statistics Department Faculty Publication Series
In the present work, we consider the self-focusing discrete nonlinear Schrödinger equation on hexagonal and honeycomb lattice geometries. Our emphasis is on the study of the effects of anisotropy, motivated by the tunability afforded in recent optical and atomic physics experiments. We find that multi-soliton and discrete vortex states undergo destabilizing bifurcations as the relevant anisotropy control parameter is varied. We quantify these bifurcations by means of explicit analytical calculations of the solutions, as well as of their spectral linearization eigenvalues. Finally, we corroborate the relevant stability picture through direct numerical computations. In the latter, we observe the prototypical manifestation …
Scattering Of Waves By Impurities In Precompressed Granular Chains, Panos Kevrekidis, Alejandro Martinez, Hiromi Yasuda, Eunho Kim, Mason Porter, Jinkyu Yang
Scattering Of Waves By Impurities In Precompressed Granular Chains, Panos Kevrekidis, Alejandro Martinez, Hiromi Yasuda, Eunho Kim, Mason Porter, Jinkyu Yang
Mathematics and Statistics Department Faculty Publication Series
We study scattering of waves by impurities in strongly precompressed granular chains. We explore the linear scattering of plane waves and identify a closed-form expression for the re ection and transmission coefficients for the scattering of the waves from both a single impurity and a double impurity. For single-impurity chains, we show that, within the transmission band of the host granular chain, high-frequency waves are strongly attenuated (such that the transmission coefficient vanishes as the wavenumber k → ± π), whereas low-frequency waves are well-transmitted through the impurity. For double-impurity chains, we identify a resonance—enabling full transmission at a particular …
Energy Criterion For The Spectral Stability Of Discrete Breathers, Panos Kevrekidis, Jesus Cuevas-Maraver, Dmitry Pelinovsky
Energy Criterion For The Spectral Stability Of Discrete Breathers, Panos Kevrekidis, Jesus Cuevas-Maraver, Dmitry Pelinovsky
Mathematics and Statistics Department Faculty Publication Series
No abstract provided.
Dark-Bright Soliton Interactions Beyond The Integrable Limit, G. Katsimiga, J. Stockhofe, Panos Kevrekidis, P. Schmelcher
Dark-Bright Soliton Interactions Beyond The Integrable Limit, G. Katsimiga, J. Stockhofe, Panos Kevrekidis, P. Schmelcher
Mathematics and Statistics Department Faculty Publication Series
In this work we present a systematic theoretical analysis regarding dark-bright solitons and their interactions, motivated by recent advances in atomic two-component repulsively interacting Bose-Einstein condensates. In particular, we study analytically via a two-soliton ansatz adopted within a variational formulation the interaction between two dark-bright solitons in a homogeneous environment beyond the integrable regime, by considering general inter/intra-atomic interaction coefficients. We retrieve the possibility of a fixed point in the case where the bright solitons are out of phase. As the inter-component interaction is increased, we also identify an exponential instability of the two-soliton state, associated with a subcritical pitchfork …
A Pt-Symmetric Dual-Core System With The Sine-Gordon Nonlinearity And Derivative Coupling, Jesus Cuevas-Maraver, Boris Malomed, Panos Kevrekidis
A Pt-Symmetric Dual-Core System With The Sine-Gordon Nonlinearity And Derivative Coupling, Jesus Cuevas-Maraver, Boris Malomed, Panos Kevrekidis
Mathematics and Statistics Department Faculty Publication Series
As an extension of the class of nonlinear PT -symmetric models, we propose a system of sine-Gordon equations, with the PT symmetry represented by balanced gain and loss in them. The equations are coupled by sine-field terms and first-order derivatives. The sinusoidal coupling stems from local interaction between adjacent particles in coupled Frenkel-Kontorova (FK) chains, while the cross-derivative coupling, which was not considered before, is induced by three-particle interactions, provided that the particles in the parallel FK chains move in different directions. Nonlinear modes are then studied in this system. In particular, kink-kink (KK) and kink-antikink (KA) complexes are explored …
Performing Hong-Ou-Mandel-Type Numerical Experiments With Repulsive Condensates: The Case Of Dark And Dark-Bright Solitons, Panos Kevrekidis, Zhi-Yuan Sun, Peter Kruger
Performing Hong-Ou-Mandel-Type Numerical Experiments With Repulsive Condensates: The Case Of Dark And Dark-Bright Solitons, Panos Kevrekidis, Zhi-Yuan Sun, Peter Kruger
Mathematics and Statistics Department Faculty Publication Series
The Hong-Ou-Mandel experiment leads indistinguishable photons simultaneously reach-ing a 50:50 beam splitter to emerge on the same port through two-photon interference.Motivated by this phenomenon, we consider numerical experiments of the same flavor forclassical, wave objects in the setting of repulsive condensates. We examine dark solitonsinteracting with a repulsive barrier, a case in which we find no significant asymmetries inthe emerging waves after the collision, presumably due to their topological nature. We alsoconsider case examples of two-component systems, where the dark solitons trap a brightstructure in the second-component (dark-bright solitary waves). For these, pronouncedasymmetries upon collision are possible for the non-topological …
Vector Dark-Antidark Solitary Waves In Multi-Component Bose-Einstein Condensates, Panos Kevrekidis, I. Danaila, M. Khamehchi, V. Gokhroo, P. Engels
Vector Dark-Antidark Solitary Waves In Multi-Component Bose-Einstein Condensates, Panos Kevrekidis, I. Danaila, M. Khamehchi, V. Gokhroo, P. Engels
Mathematics and Statistics Department Faculty Publication Series
Multi-component Bose-Einstein condensates exhibit an intriguing variety of nonlinear structures. In recent theoretical work, the notion of magnetic solitons has been introduced. Here we generalize this concept to vector dark-antidark solitary waves in multi-component Bose-Einstein condensates. We first provide concrete experimental evidence for such states in an atomic BEC and subsequently illustrate the broader concept of these states, which are based on the interplay between miscibility and inter-component repulsion. Armed with this more general conceptual framework, we expand the notion of such states to higher dimensions presenting the possibility of both vortex-antidark states and ring-antidark-ring (dark soliton) states. We perform …
Collapse For The Higher-Order Nonlinear Schrödinger Equation, V. Achilleos, S. Diamantidis, D. J. Frantzeskakis, T. P. Horikis, N. I. Karachalios, P. G. Kevrekidis
Collapse For The Higher-Order Nonlinear Schrödinger Equation, V. Achilleos, S. Diamantidis, D. J. Frantzeskakis, T. P. Horikis, N. I. Karachalios, P. G. Kevrekidis
Mathematics and Statistics Department Faculty Publication Series
We examine conditions for finite-time collapse of the solutions of the higher-order nonlinear Schrödinger (NLS) equation incorporating third-order dispersion, self-steepening, linear and nonlinear gain and loss, and Raman scattering; this is a system that appears in many physical contexts as a more realistic generalization of the integrable NLS. By using energy arguments, it is found that the collapse dynamics is chiefly controlled by the linear/nonlinear gain/loss strengths. We identify a critical value of the linear gain, separating the possible decay of solutions to the trivial zero-state, from collapse. The numerical simulations, performed for a wide class of initial data, are …
Multifrequency And Edge Breathers In The Discrete Sine-Gordon System Via Subharmonic Driving: Theory, Computation And Experiment, F. Palmero, J. Han, L. Q. English, T. J. Alexander, P. G. Kevrekidis
Multifrequency And Edge Breathers In The Discrete Sine-Gordon System Via Subharmonic Driving: Theory, Computation And Experiment, F. Palmero, J. Han, L. Q. English, T. J. Alexander, P. G. Kevrekidis
Mathematics and Statistics Department Faculty Publication Series
We consider a chain of torsionally-coupled, planar pendula shaken horizontally by an external sinusoidal driver. It has been known that in such a system, theoretically modeled by the discrete sine-Gordon equation, intrinsic localized modes, also known as discrete breathers, can exist. Recently, the existence of multifrequency breathers via subharmonic driving has been theoretically proposed and numerically illustrated by Xu et al. (2014) [21]. In this paper, we verify this prediction experimentally. Comparison of the experimental results to numerical simulations with realistic system parameters (including a Floquet stability analysis), and wherever possible to analytical results (e.g. for the subharmonic response …