James T. Pantaleone

Renormalization of the neutrino mass operator

Abstract A small neutrino Majorana mass can arise in the Standard Model as an effective dimension 5 operator. We calculate the renormalization of this operator in the minimal Standard Model and in its two-Higgs-doublet and supersymmetric extensions. Renormalization from the scale of lepton number violation (e.g., the Planck scale or a GUT scale) to the weak scale decreases the strength of this operator by an order of magnitude or more if the top quark and Higgs boson masses are large. Neutrino mixing angles also run with momentum. We show instances where small mixing at a high scale becomes large at the weak scale, and vice versa.

Synchronization of metronomes

Synchronization is a common phenomenon in physical and biological systems. We examine the synchronization of two (and more) metronomes placed on a freely moving base. The small motion of the base couples the pendulums causing synchronization. The synchronization is generally in-phase, with antiphase synchronization occurring only under special conditions. The metronome system provides a mechanical realization of the popular Kuramoto model for synchronization of biological oscillators, and is excellent for classroom demonstrations and an undergraduate physics lab.

From Chemical Gardens to Chemobrionics

Chemical gardens in laboratory chemistries ranging from silicates to polyoxometalates, in applications ranging from corrosion products to the hydration of Portland cement, and in natural settings ranging from hydrothermal vents in the ocean depths to brinicles beneath sea ice. In many chemical-garden experiments, the structure forms as a solid seed of a soluble ionic compound dissolves in a solution containing another reactive ion. In general any alkali silicate solution can be used due to their high solubility at high pH. The cation should not precipitate with the counterion of the metal salt used as seed. A main property of seed chemical-garden experiments is that initially, when the fluid is not moving under buoyancy or osmosis, the delivery of the inner reactant is diffusion controlled. Another experimental technique that isolates one aspect of chemical-garden formation is to produce precipitation membranes between different aqueous solutions by introducing the two solutions on either side of an inert carrier matrix. Chemical gardens may be grown upon injection of solutions into a so-called Hele-Shaw cell, a quasi-two-dimensional reactor consisting in two parallel plates separated by a small gap.

Neutrino oscillations in the early universe

Abstract Numerical studies are performed for neutrino oscillations for t > 1 3 seconds after the big bang. The effects of electron, positron and neutrino backgrounds are properly included. Flavor evolution of the neutrino background is dominantly smooth. However, in a certain parameter region, coherent undamped oscillations of the neutrino background are possible. In addition, neutrino CP asymmetry is found to be considerably smaller than expected. Reasons are provided for the above effects and some physical implications are discussed.

Neutrino flavor evolution near a supernova's core

In a recent paper I concluded that the neutrino background is important for calculating neutrino flavor evolution in supernovae, and including it weakens the connection between r-process nucleosynthesis and cosmologically relevant neutrino masses. Comments on this paper have been posted to this bulletin board; one by J. Cline and the other by Y.Z. Qian and G.M. Fuller. Here I briefly discuss these Comments and demonstrate that they are inaccurate and ill-considered. No corrections to my paper are necessary.

Possible violation of the equivalence principle by neutrinos.

We consider the effect of a long-range, flavor-changing tensor interaction of possible gravitational origin. Neutrino-mixing experiments provide the most sensitive probe to date for such forces{emdash}testing the equivalence principle at levels below 10{sup {minus}20}. Here we justify and generalize a formalism for describing such effects. The constraints from neutrino-mixing experiments on gravitationally induced mixing are calculated. Our detailed analysis of the atmospheric neutrino data confirms a remarkable result: the atmospheric neutrino data imply the same size violation of the equivalence principle as do the solar neutrino data. Additional tests of this suggestive result are discussed. {copyright} {ital 1996 The American Physical Society.}

Neutrino mixing due to a violation of the equivalence principle

Massless neutrinos will mix if their couplings to gravity are flavor dependent, i.e., violate the principle of equivalence. Because the gravitational interaction grows with neutrino energy, the solar neutrino problem and the recent atmospheric neutrino data may be simultaneously explained by violations at the level of 10[sup [minus]14] to 10[sup [minus]17] or smaller. This possibility is severely constrained by present accelerator neutrino experiments and will be preeminently tested in proposed long-base-line accelerator neutrino experiments.

Getting the most from atmospheric neutrinos

Observations of atmospheric neutrinos by the SuperKamiokande collaboration have demonstrated large mixing of the muon-neutrino. However the present atmospheric neutrino data does not significantly constrain the associated mixing of the electron-neutrino, or the sign of the mass-squared difference. Here we identify the diagnostics for these quantities and they also test the theory of how matter affects neutrino oscillations. These diagnostics are a dip in the sub-GeV muon flux at a zenith angle of 110 degrees, a bump in the electron up-down asymmetry at multi-GeV energies and a bump in the muon-antimuon upward asymmetry.

The added mass of a spherical projectile

When a ball moves through the air, the air exerts a force on the ball. For a sphere moving at constant velocity with respect to the air, this force is called the drag force and it has been well measured. If the sphere moves with a nonconstant velocity there are additional forces. These “unsteady” forces depend on the sphere’s acceleration and, in principle, also on higher derivatives of the motion. The force equal to a constant times the acceleration is called the “added mass” because it increases the effective inertia of the sphere moving through the fluid. We measure the unsteady forces on a sphere by observing the one- and two-dimensional projectile motion of light spheres around the highest point. The one-dimensional motion is well described by just the usual buoyant force and the added mass as calculated in the ideal fluid model. This measurement is an excellent experiment for introductory physics students. For spheres in two-dimensional projectile motion the downward vertical acceleration at the hig...

Dirac neutrino helicity flip in dense media

Abstract The effective field for a Dirac neutrino in a background of matter is derived. As an application, the cross section for helicity flip in neutrino-nucleus scattering is calculated. It is found that the matter background is negligible when the neutrino momentum is much larger than the matter induced potential. The implications of these results for a 17 keV neutrino are discussed.