David B. Kaplan

Effective field theory, black holes, and the cosmological constant

Bekenstein has proposed the bound S{le}{pi}M{sup 2}{sub P}L{sup 2} on the total entropy S in a volume L{sup 3} . This nonextensive scaling suggests that quantum field theory breaks down in large volume. To reconcile this breakdown with the success of local quantum field theory in describing observed particle phenomenology, we propose a relationship between UV and IR cutoffs such that an effective field theory should be a good description of nature. We discuss implications for the cosmological constant problem. We find a limitation on the accuracy which can be achieved by conventional effective field theory. {copyright} {ital 1999} {ital The American Physical Society}

A Method for simulating chiral fermions on the lattice

Abstract I show that a lattice theory of massive interacting fermions in 2 n +1 dimensions may be used to simulate the behavior of massless chiral fermions in 2 n dimensions if the fermion mass has a step function shape in the extra dimension. The massless states arise as zero modes bound to the mass defect, and all doublers can be given large gauge invariant masses. The manner in which the anomalies are realized is transparent: apparent chiral anomalies in the 2 n -dimensional subspace correspond to charge flow into the extra dimension.

Strange goings on in dense nucleonic matter

Abstract It has been suggested that charged pions form a Bose-Einstein condensate in baryonic matter at zero temperature and about twice nuclear density. In this letter it is shown that at somewhat higher densities one finds a charged kaon condensate, driven to a large extent by the “stgma term” interaction with baryons. Using the SU(3) × SU(3) chiral lagrangian to model meson-baryon interactions it is found that baryonic matter acquires a strangeness-per-baryon ratio approaching one at several times nuclear density. The relevance of kaon condensation as a route to strange matter and its role in neutron stars are discussed.

SU(2) × U(1) breaking by vacuum misalignment

Currently two scenarios exist which explain SU(2) × U(1) breaking: the Higgs mechanism, and standard hypercolor schemes. In this paper, a third scenario called “oblique hypercolor” is proposed. A hyperquark condensate is formed which, although kinematically allowed to point in an SU(2) × U(1) preserving direction, is forced by Yukawa interactions of the hyperquarks to misalign by a small angle, breaking SU(2) × U(1). The low energy spectrum involves normal fermions with correct masses, a partially composite Higgs boson, and physical charged scalars.

Progress in electroweak baryogenesis

Recent work on generating the excess of matter over antimatter in the early universe during the electroweak phase transition is reviewed.

The More minimal supersymmetric standard model

Abstract Effective Supersymmetry is presented as a theory of physics above the electroweak scale which has significant theoretical advantages over both the standard model and the Minimal Supersymmetric Standard Model (MSSM). The theory is supersymmetric at short distances but differs significantly from the MSSM. Flavor symmetry violation is intimately related to supersymmetry breaking. There is a new physics scale M ∼ 5–20 TeV which sets the mass of the first two sparticle families. Supersymmetric sources of CP violation and flavor changing neutral currents for the first two families are suppressed. Effective Supersymmetry can be implemented with automatic suppression of baryon and lepton number violation and a dynamically generated μ term, while maintaining naturalness in the Higgs sector. There are implications for new particle searches, flavor and CP violation experiments, as well as for the construction of theories of flavor and dynamical supersymmetry breaking.

A New expansion for nucleon-nucleon interactions

Abstract We introduce a new and well defined power counting for the effective field theory describing nucleon-nucleon interactions. Because of the large NN scattering lengths it differs from other applications of chiral perturbation theory and is facilitated by introducing an unusual subtraction scheme and renormalization group analysis. Calculation to subleading order in the expansion can be done analytically, and we present the results for both the 1 S 0 and 3 S 1 − 3 D 1 channels.

Composite Higgs Scalars

We construct models in which the Higgs doublet whose vacuum expectation breaks SU(2) × U(10 is a bound state of massive strongly interacting fermions. The couplings of the composite Higgs to ordinary fermions are induced by heavy gauge boson exchange in the manner of extended technicolor. Other heavy gauge bosons generate a negative mass term for the Higgs.

Cosmological implications of dynamical supersymmetry breaking

We provide a taxonomy of dynamical supersymmetry-breaking theories, and discuss the cosmological implications of the various types of models. Models in which supersymmetry breaking is produced by chiral superfields which only have interactions of gravitational strength (e.g., string theory moduli) are inconsistent with standard big bang nucleosynthesis unless the gravitino mass is greater than [similar to]3[times]10[sup 4] GeV. This problem cannot be solved by inflation. Models in which supersymmetry is dynamically broken by renormalizable interactions in flat space have no such cosmological problems. Supersymmetry can be broken either in a hidden or the visible sector. However, hidden sector models suffer from several naturalness problems and have difficulties in producing an acceptably large gluino mass.

Two nucleon systems from effective field theory

Abstract We elaborate on a new technique for computing properties of nucleon-nucleon interactions in terms of an effective field theory derived from low energy NN scattering data. Details of how the expansion is carried out to higher orders are presented. Analytic formulae are given for the amplitude to subleading order in both the 1 S 0 and 3 S 1 − 3 D 1 channels.