Superconducting fluctuations in small grains - the Universal Hamiltonian and the reduced BCS model

Small superconducting grains are discussed in the frameworks of both the reduced BCS Hamiltonian and the Universal Hamiltonian. It is shown that fluctuations of electrons in levels far from the Fermi energy dominate superconducting properties in small and ultrasmall grains. Experimental consequences related to the spin susceptibility and persistent currents of grains and rings with weak electron-electron interactions are discussed.Comment: Contribution to the proceedings of "Fluctuations and phase transitions in superconductors", Nazareth Ilit, Israel, June 10-14, 200

Explanatory Challenges in Metaethics

There are several important arguments in metaethics that rely on explanatory considerations. Gilbert Harman has presented a challenge to the existence of moral facts that depends on the claim that the best explanation of our moral beliefs does not involve moral facts. The Reliability Challenge against moral realism depends on the claim that moral realism is incompatible with there being a satisfying explanation of our reliability about moral truths. The purpose of this chapter is to examine these and related arguments. In particular, this chapter will discuss four kinds of arguments – Harman’s Challenge, evolutionary debunking arguments, irrelevant influence arguments, and the Reliability Challenge – understood as arguments against moral realism. The main goals of this chapter are (i) to articulate the strongest version of these arguments; (ii) to present and assess the central epistemological principles underlying these arguments; and (iii) to determine what a realist would have to do to adequately respond to these arguments

Possible Extension of the Chiral Perturbation Theory Program

After a brief discussion of how chiral dynamics has evolved from the ``universal V-A theory of weak interactions'', we present some evidence that symmetry breaking for the vector meson multiplet is not simpler than but rather analogous to that for the pseudoscalar multiplet. This provides a motivation for speculating on how to extend in a systematic way the chiral perturbation theory program to include vectors.Comment: Contribution to Marshak Memorial Volume, edited by E.C.G. Sudarshan, to be published by World Scientific, Singapore 1994, PREPRINT SU-4240-57

Introduction to effective Lagrangians for QCD

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.Comment: 12 pages, 2 figures, talk at "Compact stars in the QCD phase diagram", Copenhagen, Aug. 15-18, 200

A potential test of the CP properties and Majorana nature of neutrinos

The scattering of solar neutrinos on electrons may reveal their CP properties, which are particularly sensitive to their Majorana nature. The cross section is sensitive to the neutrino dipole moments through an interference of electro-magnetic and weak amplitudes. We show how future solar neutrino experiments with good angular resolution and low energy threshold, such as Hellaz, can be sensitive to the resulting azimuthal asymmetries in event number, and could therefore provide valuable information on the CP properties and the nature of the neutrinos, provided the solar magnetic field direction is fixed.Comment: 14 pages, 1 figure, eq. (19) corrected. Version to be publishe

Tales within Tales and Cutoffs within Cutoffs: What Sets the Mass Scale for Galaxies?

Please answer ``yes'' or ``no'': 1. Does the mass function for clusters of galaxies cut off exponentially? 2. Does the luminosity function for galaxies cut off exponentially? 3. Is the dependence of virial velocity on galaxy luminosity a power law? 4. Does the velocity function for galaxies cut off exponentially?Comment: 10 pages, no figures, contribution to the MPA/ESO/MPE/USM conference "Lighthouses of the Universe", Sunyaev et al. (eds.), ESO Astrophysics Symposia, Springer Verla

Correlated random fields in dielectric and spin glasses

Both orientational glasses and dipolar glasses possess an intrinsic random field, coming from the volume difference between impurity and host ions. We show this suppresses the glass transition, causing instead a crossover to the low $T$ phase. Moreover the random field is correlated with the inter-impurity interactions, and has a broad distribution. This leads to a peculiar variant of the Imry-Ma mechanism, with 'domains' of impurities oriented by a few frozen pairs. These domains are small: predictions of domain size are given for specific systems, and their possible experimental verification is outlined. In magnetic glasses in zero field the glass transition survives, because the random fields are disallowed by time-reversal symmetry; applying a magnetic field then generates random fields, and suppresses the spin glass transition.Comment: minor modifications, final versio

Bilinear R-parity violating SUSY: Neutrinoless double beta decay in the light of solar and atmospheric neutrino data

Neutrinoless double beta (\znbb) decay is considered within bilinear R-parity breaking supersymmetry, including the full one-loop corrections to the neutrino-neutralino mass matrix. Expected rates for \znbb decay in this model are discussed in light of recent atmospheric and solar neutrino data. We conclude that (a) tree-level calculations for \znbb decay within the bilinear model are not reliable in the range of parameters preferred by current solar and atmospheric neutrino problems. And (b) if the solar and atmospheric neutrino problems are to be solved within bilinear R-parity violating SUSY the expected rates for \znbb decay are very low; the effective Majorana neutrino mass at most 0.01 eV and typical values being one order of magnitude lower. Observing \znbb decay in the next round of experiments therefore would rule out the bilinear R-parity violating supersymmetric model as an explanation for solar and atmospheric neutrino oscillations, as well as any hierarchical scheme for neutrino masses, unless new neutrino interactions are present.Comment: 1 reference added, enlarged discussion of loop