Cosmic strings in realistic particle physics models have fermion zero modes in the string core. Such zero modes change the underlying cosmology; for example, the string can carry a current. We consider the stability of fermion zero modes to interactions with particles in the surrounding plasma. We also consider cosmological constraints on such theories, particulary those with a chiral fermion z...

We calculate the 2 fermionboson and the 4 fermion scattering amplitudes at the one loop in the NSR formulation of the heterotic and type II superstring theories using the covariant fermion emission vertex. The results are shown to agree with well known amplitudes calculated in the light-cone gauge in the GreenSchwarz formulation. The agreement of the 4 fermion amplitude entails the use of a new...

We present analytical results to guide numerical simulations with Wilson fermions in higher representations of the colour group. The ratio of Λ parameters, the additive renormalization of the fermion mass, and the renormalization of fermion bilinears are computed in perturbation theory, including cactus resummation. We recall the chiral Lagrangian for the different patterns of symmetry breaking...

According to one-loop perturbation theory, fermions whose masses are totally generated from Yukawa couplings do not decouple in the heavy mass limit. We investigate this issue nonperturbatively in the strong coupling regime of the chiral U(1) mirror-fermion model in four dimensions. Our numerical results, obtained on 6 · 16, 6 · 24 and 8 · 16 lattices, indicate nondecoupling of heavy fermion an...

We suggest that the Standard Model may undergo a supercritical transition near the Landau scale, where the U(1) gauge boson couples to the left and right handed states of any given fermion with different charges. This scenario naturally gives rise to three generations of fermion, corresponding to the three critical scales for the right-right, right-left and left-left fermion interactions going ...

We show that a dynamical supersymmetry can appear in a purely fermionic system. This " supersymmetry without bosons " is constructed by application of a recently introduced boson-fermion Dyson mapping from a fermion space to a space comprised of collective bosons and ideal fermions. In some algebraic fermion models of nuclear structure, particular Hamiltonians may lead to collective spectra of ...

I report on work done with Tomislav Prokopec (Heidelberg, CERN). We computed the one loop self-energy of a massless fermion during inflation. When the fermion is free it experiences only a small amount of inflationary particle production owing to the conformal invariance of its classical action. However, when the fermion is Yukawa coupled to a massless, minimally coupled scalar, there is copiou...

The gauge independence of the dynamical fermion mass generated through chiral symmetry breaking in QED in a strong, constant external magnetic field is critically examined. We present a (first, to the best of our knowledge) consistent truncation of the Schwinger-Dyson equations in the lowest Landau level approximation. We demonstrate that the dynamical fermion mass, obtained as the solution of ...

We study the fermion zero-mode dynamics for open strings ending on the giant graviton branes. For the open string ending on the Z = 0 brane, the quantization of the fermion zero-modes of boundary giant magnons reproduces the 256 states of the boundary degrees with the precise realization of the SU(2|2)×SU(2|2) symmetry algebra. Also for the open string ending on the Y = 0 brane, we reproduce th...