Stephen L. Adler

Photon splitting and photon dispersion in a strong magnetic field

We determine the refractive indices for photon propagation, and the absorption coefficient and polarization selection rules for photon splitting, in a strong constant magnetic field. Results are presented both in the effective Lagrangian (low frequency) approximation and in a more accurate approximation which exactly sums the vacuum polarization ring diagrams, neglecting only internal virtual photon radiative corrections. Our principal conclusion is that photon splitting can provide a mechanism for the production of linearly polarized gamma rays.

PHOTO-, ELECTRO-, AND WEAK SINGLE-PION PRODUCTION IN THE (3,3) RESONANCE REGION.

We give a unified account of single-pion photo-, electro-, and weak production. The emphases of the paper are fourfold: (1) We give a detailed kinematic discussion of single-pion electro- and weak-production; (2) we develop a dynamical model for electroproduction and weak production in the (3,3) resonance region, based on the CGLN model for photoproduction; (3) we systematically discuss the partially-conserved axail-vector current (PCAC) and current-algebra constraints which relate the single-pion electro- and weak-production matrix elements to the matrix elements for other processes; (4) we compare our model with experiment.

Chiral Symmetry Breaking in Coulomb Gauge QCD

Abstract We analyze chiral symmetry breaking in QCD in Coulomb gauge. Using the Ward identities, we derive the renormalized gap equation from the renormalized Dyson equation for the vector and axial-vector vertices. We work within the ladder approximation, in which the Bethe-Salpeter kernel is a sum of longitudinal and transverse terms, depending only on momentum transfer. This relates the chiral symmetry breaking parameters to the static quark potential. When transverse gluon exchange is neglected, our gap equation agrees in the infrared with that obtained by Amer et al. from a non-normal-ordered Coulomb gauge hamiltonian, while disagreeing with the gap equation obtained by Finger and Mandula using a normal-ordering prescription. The corrected gap equation leads to infrared-finite formulas for the effective quark and pion parameters, in which integrals for physical quantities converge for an infrared-singular confining potential V c ∞ q −4 ; we present the results of a numerical solution in this case.

Further evidence for the decay K+ ---> pi+ neutrino anti-neutrino

Additional evidence for the rare kaon decay K+ to pi+ neutrino-antineutrino has been found in a new data set with comparable sensitivity to the previously reported result. One new event was observed in the pion momentum region examined, 211<P<229 MeV/c, bringing the total for the combined data set to two. Including all data taken, the backgrounds were estimated to contribute 0.15 pm 0.05 events. The branching ratio is B=1.57^{+1.75}_{-0.82} 10^{-10}.

Why decoherence has not solved the measurement problem: A Response to P. W. Anderson

Abstract We discuss why, contrary to claims recently made by P.W. Anderson, decoherence has not solved the quantum measurement problem.

Further Evidence for the DecayK+→π+νν¯

Additional evidence for the rare kaon decay K+ to pi+ neutrino-antineutrino has been found in a new data set with comparable sensitivity to the previously reported result. One new event was observed in the pion momentum region examined, 211<P<229 MeV/c, bringing the total for the combined data set to two. Including all data taken, the backgrounds were estimated to contribute 0.15 pm 0.05 events. The branching ratio is B=1.57^{+1.75}_{-0.82} 10^{-10}.

Is Quantum Theory Exact

Future experiments may tell us if quantum mechanics is an approximation to a deeper-level theory. Quantum mechanics has enjoyed many successes since its formulation in the early 20th century. It has explained the structure and interactions of atoms, nuclei, and subnuclear particles, and has given rise to revolutionary technologies, such as integrated circuit chips and magnetic resonance imaging. At the same time, it has generated puzzles that persist to this day.

Evidence for the decay K+ ---> pi+ neutrino anti-neutrino

An event consistent with the signature expected for the rare kaon decay K+ --> pi+ nu anti-nu has been observed. In the pion momentum region examined, 211 pi+ nu anti-nu, the branching ratio is (4.2 +9.7/-3.5) x E-10.

Regularization of the stress-energy tensor for vector and scalar particles propagating in a general background metric

Abstract We study the regularization of the stress-energy tensor for massless vector and massless and massive scalar particles propagating in a general background metric, using covariant point-separation techniques. We find a prescription which leads to a stress-energy tensor which is conserved (provided, in the scalar case, that ξ = 1 6 ) and which is traceless in the conformal invariant limit. The prescription, however, is not a unique one, since the conventionally renormalized stress-energy tensor contains an undetermined multiple of a term, which can be formally reinterpreted as arising from an addition to the gravitational action which is quadratic in the Weyl curvature tensor.

Lower and upper bounds on CSL parameters from latent image formation and IGM heating

We study lower and upper bounds on the parameters for stochastic state vector reduction, focusing on the mass-proportional continuous spontaneous localization (CSL) model. We show that the assumption that the state vector is reduced when a latent image is formed, in photography or etched track detection, requires a CSL reduction rate parameter ? that is larger than conventionally assumed by a factor of roughly 2 ? 109?2, for a correlation length rC of 10?5cm. We reanalyse existing upper bounds on the reduction rate and conclude that all are compatible with such an increase in ?. The best bounds that we have obtained come from a consideration of heating of the intergalactic medium (IGM), which shows that ? can be at most ~108?1 times as large as the standard CSL value, again for rC = 10?5cm. (For both the lower and upper bounds, quoted errors are not purely statistical errors, but rather are estimates reflecting modelling uncertainties.) We discuss modifications in our analysis corresponding to a larger value of rC. With a substantially enlarged rate parameter, CSL effects may be within range of experimental detection (or refutation) with current technologies.