Interacting crumpled manifolds

In this article we study the effect of a delta-interaction on a polymerized membrane of arbitrary internal dimension D. Depending on the dimensionality of membrane and embedding space, different physical scenarios are observed. We emphasize on the difference of polymers from membranes. For the latter, non-trivial contributions appear at the 2-loop level. We also exploit a ``massive scheme'' inspired by calculations in fixed dimensions for scalar field theories. Despite the fact that these calculations are only amenable numerically, we found that in the limit of D to 2 each diagram can be evaluated analytically. This property extends in fact to any order in perturbation theory, allowing for a summation of all orders. This is a novel and quite surprising result. Finally, an attempt to go beyond D=2 is presented. Applications to the case of self-avoiding membranes are mentioned

Blackbody radiation shift in a 43Ca+ ion optical frequency standard

Motivated by the prospect of an optical frequency standard based on 43Ca+, we calculate the blackbody radiation (BBR) shift of the 4s_1/2-3d_5/2 clock transition, which is a major component of the uncertainty budget. The calculations are based on the relativistic all-order single-double method where all single and double excitations of the Dirac-Fock wave function are included to all orders of perturbation theory. Additional calculations are conducted for the dominant contributions in order to evaluate some omitted high-order corrections and estimate the uncertainties of the final results. The BBR shift obtained for this transition is 0.38(1) Hz. The tensor polarizability of the 3d_5/2 level is also calculated and its uncertainty is evaluated as well. Our results are compared with other calculations.Comment: 4 page

C-Periodicity and the Physical Mass in the 3-State Potts Model

The standard infinite-volume definition of connected correlation function and particle mass in the 3-state Potts model can be implemented in Monte Carlo simulations by using C-periodic spatial boundary conditions. This avoids both the breaking of translation invariance (cold wall b.c.) and the phase-dependent and thus possibly biased evaluation of data (periodic boundary cconditions). The numerical feasibility of the standard definitions is demonstrated by sample computations on a 24*24*48 lattice.Comment: 13 pages + 5 figures Preprint Nos. IC/93/131 and TIFR/TH/93-2

Random RNA under tension

The Laessig-Wiese (LW) field theory for the freezing transition of random RNA secondary structures is generalized to the situation of an external force. We find a second-order phase transition at a critical applied force f = f_c. For f f_c, the extension L as a function of pulling force f scales as (f-f_c)^(1/gamma-1). The exponent gamma is calculated in an epsilon-expansion: At 1-loop order gamma = epsilon/2 = 1/2, equivalent to the disorder-free case. 2-loop results yielding gamma = 0.6 are briefly mentioned. Using a locking argument, we speculate that this result extends to the strong-disorder phase.Comment: 6 pages, 10 figures. v2: corrected typos, discussion on locking argument improve

Lattice Fluid Dynamics from Perfect Discretizations of Continuum Flows

We use renormalization group methods to derive equations of motion for large scale variables in fluid dynamics. The large scale variables are averages of the underlying continuum variables over cubic volumes, and naturally live on a lattice. The resulting lattice dynamics represents a perfect discretization of continuum physics, i.e. grid artifacts are completely eliminated. Perfect equations of motion are derived for static, slow flows of incompressible, viscous fluids. For Hagen-Poiseuille flow in a channel with square cross section the equations reduce to a perfect discretization of the Poisson equation for the velocity field with Dirichlet boundary conditions. The perfect large scale Poisson equation is used in a numerical simulation, and is shown to represent the continuum flow exactly. For non-square cross sections we use a numerical iterative procedure to derive flow equations that are approximately perfect.Comment: 25 pages, tex., using epsfig, minor changes, refernces adde

2-loop Functional Renormalization for elastic manifolds pinned by disorder in N dimensions

We study elastic manifolds in a N-dimensional random potential using functional RG. We extend to N>1 our previous construction of a field theory renormalizable to two loops. For isotropic disorder with O(N) symmetry we obtain the fixed point and roughness exponent to next order in epsilon=4-d, where d is the internal dimension of the manifold. Extrapolation to the directed polymer limit d=1 allows some handle on the strong coupling phase of the equivalent N-dimensional KPZ growth equation, and eventually suggests an upper critical dimension of about 2.5.Comment: 4 pages, 3 figure

EVIDENCE OF IMMUNE STIMULATION FOLLOWING SHORT-TERM EXPOSURE TO SPECIFIC EXTREMELY LOW-FREQUENCY ELECTROMAGNETIC FIELDS

Published ArticleThere is increasing evidence that extremely low frequency (ELF) electromagnetic fields (EMFs) interact with immune cells. Even more evident is that immune cells are activated when exposed to these fields for a short period. Signal specificity and dosimetry appear to play a role. In this study, four groups of laboratory mice received daily exposure to a specific electromagnetic field with an intensity of 5μT for one hour, four hours and twenty-four hours (continuously) respectively for a period of seven days. The control group received no exposure and was used as standard for comparison. Following exposure, whole blood was analysed for leukocyte count, CD3, CD4, CD8 and CD19 analysis. The results for the twenty-four hour exposure group indicated increased total leukocyte, lymphocyte, CD3 and CD4 values and a decreased neutrophil values. These findings provide evidence that the immune system is indeed stimulated by exposure to EMFs

Interacting Crumpled Manifolds: Exact Results to all Orders of Perturbation Theory

In this letter, we report progress on the field theory of polymerized tethered membranes. For the toy-model of a manifold repelled by a single point, we are able to sum the perturbation expansion in the strength g of the interaction exactly in the limit of internal dimension D -> 2. This exact solution is the starting point for an expansion in 2-D, which aims at connecting to the well studied case of polymers (D=1). We here give results to order (2-D)^4, where again all orders in g are resummed. This is a first step towards a more complete solution of the self-avoiding manifold problem, which might also prove valuable for polymers.Comment: 8 page