Cichlid ¢shes (Cichlidae) are well suited for testing theories of the evolution of vertebrate parental care. These freshwater teleost ¢sh provide parental care for their o¡spring, display many di¡erent forms of care and have interspeci¢c variation in which sex stays with the young. Here, we assemble the ¢rst family-wide composite phylogeny based on morphological and molecular studies, and trace...

We discuss the possible signatures in the electroweak symmetry breaking sector by new strong dynamics at future hadron colliders such as the Tevatron upgrade, the LHC and VLHC, and e+e− linear colliders. Examples include a heavy Higgs-like scalar resonance, a heavy Technicolor-like vector resonance and pseudo-Goldstone states, non-resonance signatures via enhanced gauge-boson scattering and fer...

We discuss simulations with different lattice Dirac operators for sea and valence quarks. A goal of such a ‘‘mixed’’ action approach is to probe deeper the chiral regime of QCD by enabling simulations with light valence quarks. This is achieved by using chiral fermions as valence quarks while computationally inexpensive fermions are used in the sea sector. Specifically, we consider Wilson sea q...

for i = 1, · · · , N . Note that the sum over i is taken inside the parenthes before taking the square, which is not very clear in the way Peskin–Schroeder writes the Lagrangian density. I’ve put the subscript g0 to indicate that it is the bare coupling. This model describes massless spin 1/2 fermions in one spatial dimension with an attractive short-range potential. What the model does is that...

If the charm quark is sufficiently heavy, then lattice NRQCD is an efficient computational method for obtaining the spectrum of mesons with a single charm quark. Recent studies of the S and P-wave meson spectrum have determined the contributions from first, second and third order in the inverse charm mass expansion.[1,2] Second and third order contributions were found to be statistically insign...

We construct the effective action and gap equations for nonperturbative fermion 4-point functions. Our results apply to situations in which fermion masses can be ignored, which is the case for theories of strong flavor interactions involving standard quarks and leptons above the electroweak scale. The structure of the gap equations is different from what a naive generalization of the 2-point ca...

We propose an action describing chiral fermions with an arbitrary gauge group and with manifest (8, 0) worldsheet supersymmetry. The form of the action is inspired by and adapted for completing the twistor-like formulation of the D = 10 heterotic superstring. Post address: Nussallee 12 D-53115 Bonn Germany BONN-TH-94-10 Bonn University June 1994

We study excitonic states of an atomic impurity in a Fermi gas, i.e., bound states consisting of the impurity and a hole. Previous studies considered bound states of the impurity with particles from the Fermi sea where the holes formed only part of the particle-hole dressing. Within a two-channel model, we find that, for a wide range of parameters, excitonic states are not ground but metastable...

We show that under a new U(1) gauge symmetry, which is non-anomalous in the presence of one “right-handed neutrino” per generation and consistent with the standard model Yukawa couplings, the most general fermion charges are determined in terms of four rational parameters. This generalization of the B − L symmetry with generation-dependent lepton charges leads to neutrino masses induced by oper...

We construct R-invariant grand unification models with composite Higgs multiplets. Higgs doublets are massless due to the R symmetry, which is not spontaneously broken at the unification scale, while Higgs triplets get large masses from a dynamically generated superpotential, which is allowed by an R anomaly.