Statistical dynamics of spatial-order formation by communicating cells

Communicating cells can coordinate their gene expressions to form spatial patterns. 'Secrete-and-sense cells' secrete and sense the same molecule to do so and are ubiquitous. Here we address why and how these cells, from disordered beginnings, can form spatial order through a statistical mechanics-type framework for cellular communication. Classifying cellular lattices by 'macrostate' variables - 'spatial order paramete' and average gene-expression level - reveals a conceptual picture: cellular lattices act as particles rolling down on 'pseudo-energy landscapes' shaped by a 'Hamiltonian' for cellular communication. Particles rolling down represent cells' spatial order increasing. Particles trapped on the landscapes represent metastable spatial configurations. The gradient of the Hamiltonian and a 'trapping probability' determine the particle's equation of motion. This framework is extendable to more complex forms of cellular communication

Parity Nonconservation in the Photodisintegration of the Deuteron at Low Energy

The parity-nonconserving asymmetry in the deuteron photodisintegration, $\vec{\gamma}+d\to n+p$, is considered with the photon energy ranged up to 10 MeV above the threshold. The aim is to improve upon a schematic estimate assuming the absence of tensor as well as spin-orbit forces in the nucleon-nucleon interaction. The major contributions are due to the vector-meson exchanges, and the strong suppression of the pion-exchange contribution is confirmed. A simple argument, going beyond the observation of an algebraic cancellation, is presented. Contributions of meson-exchange currents are also considered, but found to be less significant.Comment: 12 pages, 6 figures, typeset by REVTeX (two-column format) and BIBTe

Parity violation in pppp scattering and vector-meson weak-coupling constants

We calculate the parity-nonconserving longitudinal asymmetry in the elastic $\vec{p} p$ scattering at the energies where experimental data are available. In addition to the standard one-meson exchange weak potential, the variation of the strong-coupling constants and the non-standard effects such as form factors and $2 \pi$-exchange description of the $\rho$-exchange potential are taken into account. With the extra effects, we investigate the compatibility of the experimental data and the presently-known range of the vector-meson weak-coupling constants.Comment: Contribution to the proceedings of the 3rd Asia-Pacific conference on few-body problems in physics, Suranaree Univ. of Technology, Nakhon Ratchasima, Thailand, July 26 - 30, 200

Deuteron Anapole Moment with Heavy Mesons

Parity-nonconserving two-body currents due to vector meson exchange are considered with the aim to determine the related contributions to the anapole moment. A particular attention is given to the requirement of current conservation which is essential for a reliable estimate of this quantity. An application is made for the deuteron case.Comment: 23 pages, 5 EPS figures, uses REVTeX 4, v2: fixes layout problem