Chiral symmetry in nuclei

Effective field theory is considered to provide a highly useful framework for connecting nuclear physics with the symmetries and dynamics of the underlying theory of strong interactions, QCD. Of many issues that are of great current interest in this domain, I concentrate here on two: (1) A new class of ab initio calculations of obsevables in two-nucleon systems; (2) Attempts to extend chiral perturbation calculations to higher-order terms.Comment: 8 pages, Invited talk at the KEK-Tanashi Symposium on Physics of Hadrons and Nuclei, December 14-17, 1998, Tokyo, Japa

Spacetime Emergence in the Robertson-Walker Universe from a Matrix model

Using a novel, string theory-inspired formalism based on a Hamiltonian constraint, we obtain a conformal mechanical system for the spatially flat four-dimensional Robertson-Walker Universe. Depending on parameter choices, this system describes either a relativistic particle in the Robertson-Walker background, or metric fluctuations of the Robertson-Walker geometry. Moreover we derive a tree-level M-theory matrix model in this time-dependent background. Imposing the Hamiltonian constraint forces the spacetime geometry to be fuzzy near the big bang, while the classical Robertson-Walker geometry emerges as the Universe expands. From our approach we also derive the temperature of the Universe interpolating between the radiation and matter dominated eras.Comment: 4 pages - accepted for publication in Physical Review Letter

Can the Electroweak Interaction Break Itself?

I examine the possibility that the electroweak interaction breaks itself via the condensation of fermions in large representations of the weak SU(2)_L gauge group.Comment: 10 pages, Latex, no figures. Published in Phys. Lett. B340, 236 (1994)

Chiral Perturbation Approach to the pp -> pp pi0 Reaction Near Threshold

The usual theoretical treatments of the near-threshold $pp \rightarrow pp\pi^0$ reaction are based on various phenomenological Lagrangians. In this work we examine the relationship between these approaches and a systematic chiral perturbation method. Our chiral perturbation calculation indicates that the pion rescattering term should be significantly enhanced as compared with the traditional phenomenological treatment, and that this term should have substantial energy and momentum dependence. An important consequence of this energy-momentum dependence is that, for a representative threshold kinematics and within the framework of our semiquantitative calculation, the rescattering term interferes destructively with the Born-term in sharp contrast to the constructive interference obtained in the conventional treatment. This destructive interference makes theoretical cross sections for $pp \rightarrow pp\pi^0$ much smaller than the experimental values, a feature that suggests the importance of the heavy-meson exchange contributions to explain the experimental data.Comment: 35 pages (REVTeX), 5 figures as 1 PostScript file acknowledgement changed, reference added, Phys.Rev.C (in print

Increasing the Fisher Information Content in the Matter Power Spectrum by Non-linear Wavelet Weiner Filtering

We develop a purely mathematical tool to recover some of the information lost in the non-linear collapse of large-scale structure. From a set of 141 simulations of dark matter density fields, we construct a non-linear Weiner filter in order to separate Gaussian and non-Gaussian structure in wavelet space. We find that the non-Gaussian power is dominant at smaller scales, as expected from the theory of structure formation, while the Gaussian counterpart is damped by an order of magnitude on small scales. We find that it is possible to increase the Fisher information by a factor of three before reaching the translinear plateau, an effect comparable to other techniques like the linear reconstruction of the density field.Comment: 7 pages, 6 figures. Accepted for publication in The Astrophysical Journa