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Articles 1 - 30 of 51
Full-Text Articles in Physical Sciences and Mathematics
Leptonic Cp Violation In A Two Parameter Model, Joseph Schechter, Samina S. Masood, Salah Nasri
Leptonic Cp Violation In A Two Parameter Model, Joseph Schechter, Samina S. Masood, Salah Nasri
Physics - All Scholarship
We further study the "complementary" Ansatz, Tr(M_\nu)=0, for a prediagonal light Majorana type neutrino mass matrix. Previously, this was studied for the CP conserving case and the case where the two Majorana type CP violating phases were present but the Dirac type CP violating phase was neglected. Here we employ a simple geometric algorithm which enables us to "solve" the Ansatz including all three CP violating phases. Specifically, given the known neutrino oscillation data and an assumed two parameter (the third neutrino mass m_3 and the Dirac CP phase \delta) family of inputs we predict the neutrino masses and Majorana …
Fixed-Connectivity Membranes, Mark Bowick
Fixed-Connectivity Membranes, Mark Bowick
Physics - All Scholarship
The statistical mechanics of flexible surfaces with internal elasticity and shape fluctuations is summarized. Phantom and self-avoiding isotropic and anisotropic membranes are discussed, with emphasis on the universal negative Poisson ratio common to the low-temperature phase of phantom membranes and all strictly self-avoiding membranes in the absence of attractive interactions. The study of crystalline order on the frozen surface of spherical membranes is also treated.
What Are The Building Blocks Of Our Universe?, Kameshwar C. Wali
What Are The Building Blocks Of Our Universe?, Kameshwar C. Wali
Physics - All Scholarship
We are told that we are living in a Golden Age of Astronomy. Cosmological Parameters are found with un precedented accuracy. Yet, the known form of matter forms only a small fraction of the total energy density of the universe. Also, a mysterious dark energy dominates the universe and causes acceleration in the rate of expansion.
In Situ Anomalous Small-Angle X-Ray Scattering From Metal Particles In Supported-Metal Catalysts. I. Theory, H. Brumberger, D. Hagrman, Jerry Goodisman, K. D. Finkelstein
In Situ Anomalous Small-Angle X-Ray Scattering From Metal Particles In Supported-Metal Catalysts. I. Theory, H. Brumberger, D. Hagrman, Jerry Goodisman, K. D. Finkelstein
Chemistry - All Scholarship
A supported-metal catalyst can be considered as a mixture of three homogeneous phases: support, void and metal. Information about the metal phase alone can be obtained using anomalous small-angle X-ray scattering (ASAXS), which requires measuring the SAXS for two different wavelengths near the metal's absorption edge. Herein, the conditions that must be obtained so that the difference between the two scattering profiles gives the scattering of the metal alone are presented. In a following contribution, the analysis will be applied to in situ ASAXS measurements made on mordenite impregnated with platinum metal while the temperature and composition of gas in …
A Geometrical Approach To N=2 Super Yang-Mills Theory On The Two Dimensional Lattice, Simon Catterall
A Geometrical Approach To N=2 Super Yang-Mills Theory On The Two Dimensional Lattice, Simon Catterall
Physics - All Scholarship
We propose a discretization of two dimensional Euclidean Yang-Mills theories with N=2 supersymmetry which preserves exactly both gauge invariance and an element of supersymmetry. The approach starts from the twisted form of the continuum super Yang Mills action which we show may be written in terms of two real Kahler-Dirac fields whose components transform into each other under the twisted supersymmetry. Once the theory is written in this geometrical language it is straightforward to discretize by mapping the component tensor fields to appropriate geometrical structures in the lattice and by replacing the continuum exterior derivative and its adjoint by appropriate …
A Spanning Tree Model For Khovanov Homology, Stephan Wehrli
A Spanning Tree Model For Khovanov Homology, Stephan Wehrli
Mathematics - All Scholarship
We use a spanning tree model to prove a result of E. S. Lee on the support of Khovanov homology of alternating knots.
Stabilizing Moduli With String Cosmology, Scott Watson
Stabilizing Moduli With String Cosmology, Scott Watson
Physics - All Scholarship
In this talk I will discuss the role of finite temperature quantum corrections in string cosmology and show that they can lead to a stabilization mechanism for the volume moduli. I will show that from the higher dimensional perspective this results from the effect of states of enhanced symmetry on the one-loop free energy. These states lead not only to stabilization, but also suggest an alternative model for cold dark matter. At late times, when the low energy effective field theory gives the appropriate description of the dynamics, the moduli will begin to slow-roll and stabilization will generically fail. However, …
Entire Pluricomplex Green Functions And Lelong Numbers Of Projective Currents, Dan Coman
Entire Pluricomplex Green Functions And Lelong Numbers Of Projective Currents, Dan Coman
Mathematics - All Scholarship
Let T be a positive closed current of bidimension (1,1) and unit masson the complex projective space Pn. We prove that the set Valpa(T) of points where T has Lelong number larger than alpha is contained in a complex line if alpha ≥ 2/3, and |V alpa(T ) \ L| ≤ 1 for some complex line L if 1/2 ≤ alpha < 2/3. We also prove that in dimension 2 and if 2/5 ≤ alpha < 1/2, then |V alpha (T ) \ C| ≤ 1 for some conic C.
Homology Over Local Homomorphisms, Luchezar L. Avramov, Srikanth Iyengar, Claudia Miller
Homology Over Local Homomorphisms, Luchezar L. Avramov, Srikanth Iyengar, Claudia Miller
Mathematics - All Scholarship
The notions of Betti numbers and of Bass numbers of a finite module N over a local ring R are extended to modules that are only assumed to be finite over S, for some local homomorphism phi: R -> S. Various techniques are developed to study the new invariants and to establish their basic properties. In several cases they are computed in closed form. Applications go in several directions. One is to identify new classes of finite R-modules whose classical Betti numbers or Bass numbers have extremal growth. Another is to transfer ring theoretical properties between R and S in …
Lattice Supersymmetry Via Twisting, Simon Catterall
Lattice Supersymmetry Via Twisting, Simon Catterall
Physics - All Scholarship
We describe how the usual supercharges of extended supersymmetry may be {\it twisted} to produce a BRST-like supercharge Q. The usual supersymmetry algebra is then replaced by a twisted algebra and the action of the twisted theory is shown to be generically Q-exact. In flat space the twisting procedure can be regarded as a change of variables carrying no physical significance. However, the twisted theories can often be transferred to the lattice while preserving the twisted supersymmetry. As an example we construct a lattice version of the two-dimensional supersymmetric sigma model
The Adjoint Of An Even Size Matrix Factors, Ragnar-Olaf Buchweitz, Graham J. Leuschke
The Adjoint Of An Even Size Matrix Factors, Ragnar-Olaf Buchweitz, Graham J. Leuschke
Mathematics - All Scholarship
We show that the adjoint matrix of a generic square matrix of even size can be factored nontrivially, answering a question of G. Bergman. This note is a preliminary report on work in progress.
Entropy And The Approach To The Thermodynamic Limit In Three-Dimensional Simplicial Gravity, Simon Catterall, John B. Kogut, R. Renken
Entropy And The Approach To The Thermodynamic Limit In Three-Dimensional Simplicial Gravity, Simon Catterall, John B. Kogut, R. Renken
Physics - All Scholarship
We present numerical results supporting the existence of an exponential bound in the dynamical triangulation model of three-dimensional quantum gravity.Both the critical coupling and various other quantities show a slow power law approach to the infinite volume limit.
Explicit Lower Bounds On The Modular Degree Of An Elliptic Curve, Mark Watkins
Explicit Lower Bounds On The Modular Degree Of An Elliptic Curve, Mark Watkins
Mathematics - All Scholarship
We derive an explicit zero-free region for symmetric square L-functions of elliptic curves, and use this to derive an explicit lower bound for the modular degree of rational elliptic curves. The techniques are similar to those used in the classical derivation of zero-free regions for Dirichlet L-functions, but here, due to the work of Goldfield-Hoffstein-Lieman, we know that there are no Siegel zeros, which leads to a strengthened result.
Study Of Leptonic Cp Violation, Joseph Schechter, Salah Nasri, Sherif Moussa
Study Of Leptonic Cp Violation, Joseph Schechter, Salah Nasri, Sherif Moussa
Physics - All Scholarship
The "complementary" Ansatz, Tr(M_\nu)=0, where M_\nu is the prediagonal neutrino mass matrix, seems a plausible approximation for capturing in a self-contained way some of the content of Grand Unification. We study its consequences in the form of relations between the neutrino masses and CP violation phases.
Bridging The Microscopic And The Hydrodynamic In Active Filament Solutions, Tanniemola B. Liverpool, M. Cristina Marchetti
Bridging The Microscopic And The Hydrodynamic In Active Filament Solutions, Tanniemola B. Liverpool, M. Cristina Marchetti
Physics - All Scholarship
Hydrodynamic equations for an isotropic solution of active polar filaments are derived from a microscopic mean-field model of the forces exchanged between motors and filaments. We find that a spatial dependence of the motor stepping rate along the filament is essential to drive bundle formation. A number of differences arise as compared to hydrodynamics derived (earlier) from a mesoscopic model where relative filament velocities were obtained on the basis of symmetry considerations. Due to the anisotropy of filament diffusion, motors are capable of generating net filament motion relative to the solvent. The effect of this new term on the stability …
Simulations Of Dynamically Triangulated Gravity -- An Algorithm For Arbitrary Dimension, Simon Catterall
Simulations Of Dynamically Triangulated Gravity -- An Algorithm For Arbitrary Dimension, Simon Catterall
Physics - All Scholarship
Recent models for discrete euclidean quantum gravity incorporate a sum over simplicial triangulations. We describe an algorithm for simulating such models in general dimensions. As illustration we show results from simulations in four dimensions
Could Dark Energy Be Vector-Like?, Christian Armendariz-Picon
Could Dark Energy Be Vector-Like?, Christian Armendariz-Picon
Physics - All Scholarship
In this paper I explore whether a vector field can be the origin of the present stage of cosmic acceleration. In order to avoid violations of isotropy, the vector has be part of a ``cosmic triad'', that is, a set of three identical vectors pointing in mutually orthogonal spatial directions. A triad is indeed able to drive a stage of late accelerated expansion in the universe, and there exist tracking attractors that render cosmic evolution insensitive to initial conditions. However, as in most other models, the onset of cosmic acceleration is determined by a parameter that has to be tuned …
Lattice Sigma Models With Exact Supersymmetry, Simon Catterall, Sofiane Ghadab
Lattice Sigma Models With Exact Supersymmetry, Simon Catterall, Sofiane Ghadab
Physics - All Scholarship
We show how to construct lattice sigma models in one, two and four dimensions which exhibit an exact fermionic symmetry. These models are discretized and {\it twisted} versions of conventional supersymmetric sigma models with N=2 supersymmetry. The fermionic symmetry corresponds to a scalar BRST charge built from the original supercharges. The lattice theories possess local actions and in many cases admit a Wilson term to suppress doubles. In the two and four dimensional theories we show that these lattice theories are invariant under additional discrete symmetries. We argue that the presence of these exact symmetries ensures that no fine tuning …
Elliptic Curves Of Large Rank And Small Conductor, Noam D. Elkies, Mark Watkins
Elliptic Curves Of Large Rank And Small Conductor, Noam D. Elkies, Mark Watkins
Mathematics - All Scholarship
For r=6,7,...,11 we find an elliptic curve E/Q of rank at least r and the smallest conductor known, improving on the previous records by factors ranging from 1.0136 (for r=6) to over 100 (for r=10 and r=11). We describe our search methods, and tabulate, for each r=5,6,...,11, the five curves of lowest conductor, and (except for r=11) also the five of lowest absolute discriminant, that we found.
Experimental And Theoretical Studies On The Pharmacodynamics Of Cisplatin In Jurkat Cells, Kirk A. Tacka, Dava Szalda, Abdul-Kader Souid, Jerry Goodisman, James C. Dabrowiak
Experimental And Theoretical Studies On The Pharmacodynamics Of Cisplatin In Jurkat Cells, Kirk A. Tacka, Dava Szalda, Abdul-Kader Souid, Jerry Goodisman, James C. Dabrowiak
Chemistry - All Scholarship
For Jurkat cells in culture exposed to cisplatin (1), we measured the number of platinum adducts on DNA and showed that it is proportional to the AUC, the area under the concentration vs time curve, for cisplatin. The number of platinum-DNA adducts is measured immediately following exposure to drug. The AUC is calculated either as the product of the initial cisplatin concentration and the exposure time or as the integral under the concentration vs time curve for the unreacted dichloro species, which decreases exponentially. We also show that the number of adducts correlates with decreases in respiration, with the amount …
Moduli Stabilization With The String Higgs Effect, Scott Watson
Moduli Stabilization With The String Higgs Effect, Scott Watson
Physics - All Scholarship
We review the notion of the Higgs effect in the context of string theory. We find that by including this effect in time dependent backgrounds, one is led to a natural mechanism for stabilizing moduli at points of enhanced gauge symmetry. We consider this mechanism for the case of the radion (size of the extra dimensions) and find that as decompactification of the large spatial dimensions takes place the radion will remain stabilized at the self dual radius. We discuss how this mechanism can be incorporated into models of string cosmology and brane inflation to resolve some outstanding problems. We …
Decoherence In Josephson-Junction Qubits Due To Critical Current Fluctuations, Britton Plourde, D. J. Van Harlingen
Decoherence In Josephson-Junction Qubits Due To Critical Current Fluctuations, Britton Plourde, D. J. Van Harlingen
Physics - All Scholarship
We compute the decoherence caused by 1/f fluctuations at low frequency f in the critical current I_0 of Josephson junctions incorporated into flux, phase, charge and hybrid flux-charge superconducting quantum bits (qubits). The dephasing time \tau_{\phi} scales as I_0/ \Omega \Lambda S_{I_0}^{1/2}(1 Hz),where \Omega / 2\pi is the energy level splitting frequency, S_{I_0}(1 Hz) is the spectral density of the critical current noise at 1 Hz, and \Lambda \equiv |I_0 d \Omega / \Omega d I_0| is a parameter computed for given parameters for each type of qubit that specifies the sensitivity of the level splitting to critical current fluctuations. …
Two Theorems About Maximal Cohen--Macaulay Modules, Craig Huneke, Graham J. Leuschke
Two Theorems About Maximal Cohen--Macaulay Modules, Craig Huneke, Graham J. Leuschke
Mathematics - All Scholarship
This paper contains two theorems concerning the theory of maximal Cohen-Macaulay modules. The first theorem proves that certain Ext groups between maximal Cohen-Macaulay modules M and N must have finite length, provided only finitely many isomorphism classes of maximal Cohen-Macaulay modules exist having ranks up to the sum of the ranks of M and N. This has several corollaries. In particular it proves that a Cohen-Macaulay local ring of finite Cohen-Macaulay type has an isolated singularity. A well-known theorem of Auslander gives the same conclusion but requires that the ring be Henselian. Other corollaries of our result include statements concerning …
Transcendence Measures And Algebraic Growth Of Entire Functions, Dan Coman, Evgeny A. Poletsky
Transcendence Measures And Algebraic Growth Of Entire Functions, Dan Coman, Evgeny A. Poletsky
Mathematics - All Scholarship
In this paper we obtain estimates for certain transcendence measures of an entire function f. Using these estimates, we prove Bernstein, doubling and Markov inequalities for a polynomial P(z,w) in C2 along the graph of f. These inequalities provide, in turn, estimates for the number of zeros of the function P(z, f(z)) in the disk of radius r, in terms of the degree of P and of r. Our estimates hold for arbitrary entire functions f of finite order, and for a subsequence {nj} of degrees of polynomials. But for special classes of functions, including the Riemann zeta-function, they hold …
Improved Extremal Optimization For The Ising Spin Glass, Alan Middleton
Improved Extremal Optimization For The Ising Spin Glass, Alan Middleton
Physics - All Scholarship
A version of the extremal optimization (EO) algorithm introduced by Boettcher and Percus is tested on 2D and 3D spin glasses with Gaussian disorder. EO preferentially flips spins that are locally ``unfit''; the variant introduced here reduces the probability to flip previously selected spins. Relative to EO, this adaptive algorithm finds exact ground states with a speed-up of order $10^{4}$ ($10^{2}$) for $16^{2}$- ($8^{3}$-) spin samples. This speed-up increases rapidly with system size, making this heuristic a useful tool in the study of materials with quenched disorder.
Effective Field Theory Approach To String Gas Cosmology, Scott Watson, Thorsten Battefeld
Effective Field Theory Approach To String Gas Cosmology, Scott Watson, Thorsten Battefeld
Physics - All Scholarship
We derive the 4D low energy effective field theory for a closed string gas on a time dependent FRW background. We examine the solutions and find that although the Brandenberger-Vafa mechanism at late times no longer leads to radion stabilization, the radion rolls slowly enough that the scenario is still of interest. In particular, we find a simple example of the string inspired dark matter recently proposed by Gubser and Peebles.
Quasianalyticity And Pluripolarity, Dan Coman, Norman Levenberg, Evgeny A. Poletsky
Quasianalyticity And Pluripolarity, Dan Coman, Norman Levenberg, Evgeny A. Poletsky
Mathematics - All Scholarship
We show that the graph gamma f = {(z, f(z)) in C2 : z in S} in C2 of a function f on the unit circle S which is either continuous and quasianalytic in the sense of Bernstein or C1 and quasianalytic in the sense of Denjoy is pluripolar.
Smooth Submanifolds Intersecting Any Analytic Curve In A Discrete Set, Dan Coman, Norman Levenberg, Evgeny A. Poletsky
Smooth Submanifolds Intersecting Any Analytic Curve In A Discrete Set, Dan Coman, Norman Levenberg, Evgeny A. Poletsky
Mathematics - All Scholarship
We construct examples of Cinifinity smooth submanifolds in Cn and Rn of codimension 2 and 1, which intersect every complex, respectively real, analytic curve in a discrete set. The examples are realized either as compact tori or as properly imbedded Euclidean spaces, and are the graphs of quasianalytic functions. In the complex case, these submanifolds contain real n-dimensional tori or Euclidean spaces that are not pluripolar while the intersection with any complex analytic disk is polar.
Leptonic Cp Violation Phases Using An Ansatz For The Neutrino Mass Matrix And Application To Leptogenesis, Joseph Schechter, Salah Nasri, Sherif Moussa
Leptonic Cp Violation Phases Using An Ansatz For The Neutrino Mass Matrix And Application To Leptogenesis, Joseph Schechter, Salah Nasri, Sherif Moussa
Physics - All Scholarship
We further study the previously proposed Ansatz, Tr(M)=0, for a prediagonal light Majorana type neutrino mass matrix. If CP violation is neglected this enables one to use the existing data on squared mass differences to estimate (up to a discrete ambiguity)the neutrino masses themselves. If it is assumed that only the conventional CP phase is present, the ansatz enables us to estimate this phase in addition to all three masses. If it is assumed that only the two Majorana CP phases are present, the Ansatz enables us to obtain a one parameter family of solutions for the masses and phases. …
Non-Adiabatic Perturbations From Single-Field Inflation, Christian Armendariz-Picon
Non-Adiabatic Perturbations From Single-Field Inflation, Christian Armendariz-Picon
Physics - All Scholarship
If the inflaton decays into several components during reheating, and if the corresponding decay rates are functions of spacetime-dependent quantities, it is possible to generate entropy perturbations after a stage of single-field inflation. In this paper, I present a simple toy example that illustrates this possibility. In the example, the decay rates of the inflaton into ``matter'' and ``radiation'' are different functions of the total energy density. In particular cases, one can exactly solve the equations of motion both for background and perturbations in the long-wavelength limit, and show that entropy perturbations do indeed arise. Beyond these specific examples, I …