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Full-Text Articles in Physics
Measuring The Speed Of Sound Of Quintessence, Christian Armendariz-Picon, Joel K. Erickson, R. R. Caldwell, Paul J. Steinhardt, V. Mukhanov
Measuring The Speed Of Sound Of Quintessence, Christian Armendariz-Picon, Joel K. Erickson, R. R. Caldwell, Paul J. Steinhardt, V. Mukhanov
Physics - All Scholarship
Quintessence, a time-varying energy component that may account for the accelerated expansion of the universe, can be characterized by its equation of state and sound speed. In this paper, we show that if the quintessence density is at least one percent of the critical density at the surface of last scattering the cosmic microwave background anisotropy can distinguish between models whose sound speed is near the speed of light versus near zero, which could be useful in distinguishing competing candidates for dark energy.
Testing A Fourier Accelerated Hybrid Monte Carlo Algorithm, Simon Catterall, Sergey Karamov
Testing A Fourier Accelerated Hybrid Monte Carlo Algorithm, Simon Catterall, Sergey Karamov
Physics - All Scholarship
We describe a Fourier Accelerated Hybrid Monte Carlo algorithm suitable for dynamical fermion simulations of non-gauge models. We test the algorithm in supersymmetric quantum mechanics viewed as a one-dimensional Euclidean lattice field theory. We find dramatic reductions in the autocorrelation time of the algorithm in comparison to standard HMC.
Introduction To Effective Lagrangians For Qcd, Joseph Schechter
Introduction To Effective Lagrangians For Qcd, Joseph Schechter
Physics - All Scholarship
A brief introduction to the effective Lagrangian treatment of QCD (in the sense of using fields representing physical particles rather than quarks and gluons) will be given. The historical evolution of the subject will be discussed. Some background material related to a recent model for Gamma Ray Bursters will be given. Finally, some recent work on low energy strong interactions will be mentioned.
Anomaly Induced Qcd Potential And Quark Decoupling, Joseph Schechter, Stephen D.H. Hsu, Francesco Sannino
Anomaly Induced Qcd Potential And Quark Decoupling, Joseph Schechter, Stephen D.H. Hsu, Francesco Sannino
Physics - All Scholarship
We explore the anomaly induced effective QCD meson potential in the framework of the effective Lagrangian approach. We suggest a decoupling procedure, when a flavored quark becomes massive, which mimics the one employed by Seiberg for supersymmetric gauge theories. It is seen that, after decoupling, the QCD potential naturally converts to the one with one less flavor. We study the N_c and N_f dependence of the \eta^{\prime} mass.
The Formation Of Vortex Loops (Strings) In Continuous Phase Transitions, Mark Bowick, Angelo Cacciuto, Alex Travesset
The Formation Of Vortex Loops (Strings) In Continuous Phase Transitions, Mark Bowick, Angelo Cacciuto, Alex Travesset
Physics - All Scholarship
The formation of vortex loops (global cosmic strings) in an O(2) linear sigma model in three spatial dimensions is analyzed numerically. For over-damped Langevin dynamics we find that defect production is suppressed by an interaction between correlated domains that reduces the effective spatial variation of the phase of the order field. The degree of suppression is sensitive to the quench rate. A detailed description of the numerical methods used to analyze the model is also reported.
Complementary Ansatz For The Neutrino Mass Matrix, Joseph Schechter, Deirdre Black, Amir H. Fariborz, Salah Nasri
Complementary Ansatz For The Neutrino Mass Matrix, Joseph Schechter, Deirdre Black, Amir H. Fariborz, Salah Nasri
Physics - All Scholarship
We propose a simple Ansatz for the three generation neutrino mass matrix M_\nu which is motivated from an SO(10) grand unified theory. The Ansatz can be combined with information from neutrino oscillation experiments and bounds on neutrinoless double beta decay to determine the neutrino masses themselves and to reconstruct, with some assumptions, the matrix M_\nu.
Investigating The Light Scalar Mesons, Joseph Schechter, D. Black, Amir H. Fariborz, Salah Moussa, S. Nasri
Investigating The Light Scalar Mesons, Joseph Schechter, D. Black, Amir H. Fariborz, Salah Moussa, S. Nasri
Physics - All Scholarship
We first briefly review a treatment of the scalars in meson meson scattering based on a non-linear chiral Lagrangian, with unitarity implemented by a "local" modification of the scalar propagators. It is shown that the main results are confirmed by a treatment in the SU(3) linear sigma model in which unitarity is implemented "globally". Some remarks are made on the speculative subject of the scalars' quark structure.
A Two-Dimensional Lattice Model With Exact Supersymmetry, Simon Catterall, S. Karamov
A Two-Dimensional Lattice Model With Exact Supersymmetry, Simon Catterall, S. Karamov
Physics - All Scholarship
Starting from a simple discrete model which exhibits a supersymmetric invariance we construct a local, interacting, two-dimensional Euclidean lattice theory which also admits an exact supersymmetry. This model is shown to correspond to the Wess-Zumino model with extended N=2 supersymmetry in the continuum. We have performed dynamical fermion simulations to check the spectrum and supersymmetric Ward identities and find good agreement with theory.
Universal Negative Poisson Ratio Of Self Avoiding Fixed Connectivity Membranes, Mark Bowick, Angelo Cacciuto, G. Thorleifsson, A. Travesset
Universal Negative Poisson Ratio Of Self Avoiding Fixed Connectivity Membranes, Mark Bowick, Angelo Cacciuto, G. Thorleifsson, A. Travesset
Physics - All Scholarship
We determine the Poisson ratio of self-avoiding fixed-connectivity membranes, modeled as impenetrable plaquettes, to be sigma=-0.37(6), in statistical agreement with the Poisson ratio of phantom fixed-connectivity membranes sigma=-0.32(4). Together with the equality of critical exponents, this result implies a unique universality class for fixed-connectivity membranes. Our findings thus establish that physical fixed-connectivity membranes provide a wide class of auxetic (negative Poisson ratio) materials with significant potential applications in materials science.
The Three-Dimensional Random Field Ising Magnet: Interfaces, Scaling, And The Nature Of States, Alan Middleton, Daniel S. Fisher
The Three-Dimensional Random Field Ising Magnet: Interfaces, Scaling, And The Nature Of States, Alan Middleton, Daniel S. Fisher
Physics - All Scholarship
The nature of the zero temperature ordering transition in the 3D Gaussian random field Ising magnet is studied numerically, aided by scaling analyses. In the ferromagnetic phase the scaling of the roughness of the domain walls, $w\sim L^\zeta$, is consistent with the theoretical prediction $\zeta = 2/3$. As the randomness is increased through the transition, the probability distribution of the interfacial tension of domain walls scales as for a single second order transition. At the critical point, the fractal dimensions of domain walls and the fractal dimension of the outer surface of spin clusters are investigated: there are at least …
Doubly Perturbed S_3 Neutrinos And The S_{13} Mixing Parameter, Joseph Schechter, Renata Jora, M. Naeem Shahid
Doubly Perturbed S_3 Neutrinos And The S_{13} Mixing Parameter, Joseph Schechter, Renata Jora, M. Naeem Shahid
Physics - All Scholarship
We further study a predictive model for the masses and mixing matrix of three Majorana neutrinos. At zeroth order the model yielded degenerate neutrinos and a generalized ``tribimaximal" mixing matrix. At first order the mass splitting was incorporated and the tribimaximal mixing matrix emerged with very small corrections but with a zero value for the parameter $s_{13}$. In the present paper a different, assumed weaker, perturbation is included which gives a non zero value for $s_{13}$ and further corrections to other quantities. These corrections are worked out and their consequences discussed under the simplifying assumption that the conventional CP violation …
Remark On Pion Scattering Lengths, Joseph Schechter, Deirdre Black, Nae Woong Park
Remark On Pion Scattering Lengths, Joseph Schechter, Deirdre Black, Nae Woong Park
Physics - All Scholarship
First it is shown that the tree amplitude for pion pion scattering in the minimal linear sigma model has an exact expression which is proportional to a geometric series in the quantity (s-$m_\pi^2$)/($m_B^2-m_\pi^2$), where $m_B$ is the sigma mass which appears in the Lagrangian and is the only a priori unknown parameter in the model. This induces an infinite series for every predicted scattering length in which each term corresponds to a given order in the chiral perturbation theory counting. It is noted that, perhaps surprisingly, the pattern, though not the exact values, of chiral perturbation theory predictions for both …
The Ising Model On A Dynamically Triangulated Disk With A Boundary Magnetic Field, Simon Catterall, Scott V. Mcguire, Mark Bowick, Simeon Warner
The Ising Model On A Dynamically Triangulated Disk With A Boundary Magnetic Field, Simon Catterall, Scott V. Mcguire, Mark Bowick, Simeon Warner
Physics - All Scholarship
We use Monte Carlo simulations to study a dynamically triangulated disk with Ising spins on the vertices and a boundary magnetic field. For the case of zero magnetic field we show that the model possesses three phases. For one of these the boundary length grows linearly with disk area, while the other two phases are characterized by a boundary whose size is on the order of the cut-off. A line of continuous magnetic transitions separates the two small boundary phases. We determine the critical exponents of the continuous magnetic phase transition and relate them to predictions from continuum 2-d quantum …
The Geometrical Structure Of 2d Bond-Orientational Order, Mark Bowick, Alex Travesset
The Geometrical Structure Of 2d Bond-Orientational Order, Mark Bowick, Alex Travesset
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We study the formulation of bond-orientational order in an arbitrary two dimensional geometry. We find that bond-orientational order is properly formulated within the framework of differential geometry with torsion. The torsion reflects the intrinsic frustration for two-dimensional crystals with arbitrary geometry. Within a Debye-Huckel approximation, torsion may be identified as the density of dislocations. Changes in the geometry of the system cause a reorganization of the torsion density that preserves bond-orientational order. As a byproduct, we are able to derive several identities involving the topology, defect density and geometric invariants such as Gaussian curvature. The formalism is used to derive …
Universality Classes Of Self-Avoiding Fixed-Connectivity Membranes, Mark Bowick, Angelo Cacciuto, Gudmar Thorleifsson, Alex Travesset
Universality Classes Of Self-Avoiding Fixed-Connectivity Membranes, Mark Bowick, Angelo Cacciuto, Gudmar Thorleifsson, Alex Travesset
Physics - All Scholarship
We present an analysis of extensive large-scale Monte Carlo simulations of self-avoiding fixed-connectivity membranes for sizes (number of faces) ranging from 512 to 17672 (triangular) plaquettes. Self-avoidance is implemented via impenetrable plaquettes. We simulate the impenetrable plaquette model in both three and four bulk dimensions. In both cases we find the membrane to be flat for all temperatures: the size exponent in three dimensions is nu=0.95(5) (Hausdorff dimension d_H=2.1(1)). The single flat phase appears, furthermore, to be equivalent to the large bending rigidity phase of non-self-avoiding fixed-connectivity membranes - the roughness exponent in three dimensions is xi=0.63(4). This suggests that …