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## Full-Text Articles in Physics

Hyperfine Splitting Of Low-Lying Heavy Baryons, Joseph Schechter, Masayasu Harada, Asif Qamar, Francesco Sannino, Herbert Weigel

#### Hyperfine Splitting Of Low-Lying Heavy Baryons, Joseph Schechter, Masayasu Harada, Asif Qamar, Francesco Sannino, Herbert Weigel

*Physics*

We calculate the next-to-leading order contribution to the masses of the heavy baryons in the bound state approach for baryons containing a heavy quark. These 1/N_C corrections arise when states of good spin and isospin are generated from the background soliton of the light meson fields. Our study is motivated by the previously established result that light vector meson fields are required for this soliton in order to reasonably describe the spectrum of both the light and the heavy baryons. We note that the inclusion of light vector mesons significantly improves the agreement of the predicted hyperfine splitting with ...

Phase Structure Of Dynamical Triangulation Models In Three Dimensions, Simon Catterall, Ray L. Renken, John B. Kogut

#### Phase Structure Of Dynamical Triangulation Models In Three Dimensions, Simon Catterall, Ray L. Renken, John B. Kogut

*Physics*

The dynamical triangulation model of three-dimensional quantum gravity is shown to have a line of transitions in an expanded phase diagram which includes a coupling mu to the order of the vertices. Monte Carlo renormalization group and finite size scaling techniques are used to locate and characterize this line. Our results indicate that for mu < mu1 ~ -1.0 the model is always in a crumpled phase independent of the value of the curvature coupling. For mu < 0 the results are in agreement with an approximate mean field treatment. We find evidence that this line corresponds to first order transitions extending to positive mu. However, the behavior appears to change for mu > mu2 ~ 2-4. The simplest scenario that is consistent with the data is the existence of a critical end point.

Remark On The Potential Function Of The Linear Sigma Model, Joseph Schechter, David Delphenich

#### Remark On The Potential Function Of The Linear Sigma Model, Joseph Schechter, David Delphenich

*Physics*

It is shown that the potential functions for the ordinary linear sigma model can be divided into two topographically different types depending on whether the quantity R\equiv (m_\sigma /m_\pi)^2 is greater than or less than nine. Since the Wigner-Weyl mode (R=1) and the Nambu-Goldstone mode (R=\infty belong to different regions, we speculate that this classification may provide a generalization to the broken symmetry situation, which could be convenient for roughly characterizing different possible applications of the model. It is noted that a more complicated potential does not so much change this picture as add ...

Effects Of Self-Avoidance On The Tubular Phase Of Anisotropic Membranes, Mark Bowick, Emmanuel Guitter

#### Effects Of Self-Avoidance On The Tubular Phase Of Anisotropic Membranes, Mark Bowick, Emmanuel Guitter

*Physics*

We study the tubular phase of self-avoiding anisotropic membranes. We discuss the renormalizability of the model Hamiltonian describing this phase and derive from a renormalization group equation some general scaling relations for the exponents of the model. We show how particular choices of renormalization factors reproduce the Gaussian result, the Flory theory and the Gaussian Variational treatment of the problem. We then study the perturbative renormalization to one loop in the self-avoiding parameter using dimensional regularization and an epsilon-expansion about the upper critical dimension, and determine the critical exponents to first order in epsilon.

Singular Structure In 4d Simplicial Gravity, Simon Catterall, R. Renken, John B. Kogut

#### Singular Structure In 4d Simplicial Gravity, Simon Catterall, R. Renken, John B. Kogut

*Physics*

We show that the phase transition previously observed in dynamical triangulation models of quantum gravity can be understood as being due to the creation of a singular link. The transition between singular and non-singular geometries as the gravitational coupling is varied appears to be first order.

Statistical Topography Of Glassy Interfaces, Alan Middleton, Chen Zeng, Jane Kondev, David Mcnamara

#### Statistical Topography Of Glassy Interfaces, Alan Middleton, Chen Zeng, Jane Kondev, David Mcnamara

*Physics*

Statistical topography of two-dimensional interfaces in the presence of quenched disorder is studied utilizing combinatorial optimization algorithms. Finite-size scaling is used to measure geometrical exponents associated with contour loops and fully packed loops. We find that contour-loop exponents depend on the type of disorder (periodic ``vs'' non-periodic) and they satisfy scaling relations characteristic of self-affine rough surfaces. Fully packed loops on the other hand are unaffected by disorder with geometrical exponents that take on their pure values.

Toy Model For Breaking Super Gauge Theories At The Effective Lagrangian Level, Joseph Schechter, Francesco Sannino

#### Toy Model For Breaking Super Gauge Theories At The Effective Lagrangian Level, Joseph Schechter, Francesco Sannino

*Physics*

We propose a toy model to illustrate how the effective Lagrangian for super QCD might go over to the one for ordinary QCD by a mechanism whereby the gluinos and squarks in the fundamental theory decouple below a given supersymmetry breaking scale m. The implementation of this approach involves a suitable choice of possible supersymmetry breaking terms. An amusing feature of the model is the emergence of the ordinary QCD degrees of freedom which were hidden in the auxiliary fields of the supersymmetric effective Lagrangian.

Numerical Observation Of A Tubular Phase In Anisotropic Membranes, Mark Bowick, Marco Falcioni, Gudmar Thorleifsson

#### Numerical Observation Of A Tubular Phase In Anisotropic Membranes, Mark Bowick, Marco Falcioni, Gudmar Thorleifsson

*Physics*

We provide the first numerical evidence for the existence of a tubular phase, predicted by Radzihovsky and Toner (RT), for anisotropic tethered membranes without self-avoidance. Incorporating anisotropy into the bending rigidity of a simple model of a tethered membrane with free boundary conditions, we show that the model indeed has two phase transitions corresponding to the flat-to-tubular and tubular-to-crumpled transitions. For the tubular phase we measure the Flory exponent \nu_F and the roughness exponent \zet. We find \nu_F=0.305(14) and \zeta=0.895(60), which are in reasonable agreement with the theoretical predictions of RT --- \nu_F=1/4 ...

Efficiency Of Molecular Hydrogen Formation On Silicates, Gianfranco Vidali, Valerio Pirronello, Ofer Biham, Chi Liu, Lyiong Shen

#### Efficiency Of Molecular Hydrogen Formation On Silicates, Gianfranco Vidali, Valerio Pirronello, Ofer Biham, Chi Liu, Lyiong Shen

*Physics*

We report on laboratory measurements of molecular hydrogen formation and recombination on an olivine slab as a function of surface temperature under conditions relevant to those encountered in the interstellar medium. On the basis of our experimental evidence, we recognize that there are two main regimes of H coverage that are of astrophysical importance; for each of them we provide an expression giving the production rate of molecular hydrogen in interstellar clouds.

Multiflavor Massive Schwinger Model With Non-Abelian Bosonization, Joseph Schechter, David Delphenich

#### Multiflavor Massive Schwinger Model With Non-Abelian Bosonization, Joseph Schechter, David Delphenich

*Physics*

We revisit the treatment of the multiflavor massive Schwinger model by non-Abelian Bosonization. We compare three different approximations to the low-lying spectrum: i) reading it off from the bosonized Lagrangian (neglecting interactions), ii) semi-classical quantization of the static soliton, iii) approximate semi-classical quantization of the ``breather'' solitons. A number of new points are made in this process. We also suggest a different ``effective low-energy Lagrangian'' for the theory which permits easy calculation of the low-energy scattering amplitudes. It correlates an exact mass formula of the system with the requirement of the Mermin-Wagner theorem.

Generalization Of The Bound State Model, Joseph Schechter, Masayasu Harada, Francesco Sannino, Herbert Weigel

#### Generalization Of The Bound State Model, Joseph Schechter, Masayasu Harada, Francesco Sannino, Herbert Weigel

*Physics*

In the bound state approach the heavy baryons are constructed by binding, with any orbital angular momentum, the heavy meson multiplet to the nucleon considered as a soliton in an effective meson theory. We point out that this picture misses an entire family of states, labeled by a different angular momentum quantum number, which are expected to exist according to the geometry of the three-body constituent quark model (for N_C=3). To solve this problem we propose that the bound state model be generalized to include orbitally excited heavy mesons bound to the nucleon. In this approach the missing angular ...

Minimal Dynamical Triangulations Of Random Surfaces, Mark Bowick, Simon Catterall, Gudmar Thorleifsson

#### Minimal Dynamical Triangulations Of Random Surfaces, Mark Bowick, Simon Catterall, Gudmar Thorleifsson

*Physics*

We introduce and investigate numerically a minimal class of dynamical triangulations of two-dimensional gravity on the sphere in which only vertices of order five, six or seven are permitted. We show firstly that this restriction of the local coordination number, or equivalently intrinsic scalar curvature, leaves intact the fractal structure characteristic of generic dynamically triangulated random surfaces. Furthermore the Ising model coupled to minimal two-dimensional gravity still possesses a continuous phase transition. The critical exponents of this transition correspond to the usual KPZ exponents associated with coupling a central charge c=1/2 model to two-dimensional gravity.

Minimal Dynamical Triangulations Of Random Surfaces, Simon Catterall, Mark Bowick, Gudmar Thorleifsson

#### Minimal Dynamical Triangulations Of Random Surfaces, Simon Catterall, Mark Bowick, Gudmar Thorleifsson

*Physics*

No abstract provided.

The Poisson Ratio Of Crystalline Surfaces, Marco Falcioni, Mark Bowick, Emmanuel Guitter, Gudmar Thorleifsson

#### The Poisson Ratio Of Crystalline Surfaces, Marco Falcioni, Mark Bowick, Emmanuel Guitter, Gudmar Thorleifsson

*Physics*

A remarkable theoretical prediction for a crystalline (polymerized) surface is that its Poisson ratio (\sigma) is negative. Using a large scale Monte Carlo simulation of a simple model of such surfaces we show that this is indeed true. The precise numerical value we find is (\sigma \simeq -0.32) on a (128^2) lattice at bending rigidity (kappa = 1.1). This is in excellent agreement with the prediction (\sigma = -1/3) following from the self-consistent screening approximation of Le Doussal and Radzihovsky.