arXiv subjects

Anthony G Williams

Publications and source records attributed to Anthony G Williams.

3 recordsLinked to original sources

arXiv2017

Effect of electromagnetic dipole dark matter on energy transport in the solar interior

In recent years, a revised set of solar abundances has led to a discrepancy in the sound-speed profile between helioseismology and theoretical solar models. Conventional solutions require additional mechanisms for energy transport within the Sun. Vincent et al. have recently suggested that dark matter with a momentum or velocity dependent cross section could provide a solution. In this work, we consider three models of dark matter with such cross sections and their effect on the stellar structure. In particular, the three models incorporate dark matter particles interacting through an electromagnetic dipole moment: an electric dipole, a magnetic dipole or an anapole. Each model is implemented in the \texttt{DarkStec} stellar evolution program, which incorporates the effects of dark matter capture and heat transport within the solar interior. We show that dark matter with an anapole moment of $\sim1\mathrm{GeV}^{-2}$ or magnetic dipole moment of $\sim10^{-3}μ_p$ can improve the sound-speed profile, small frequency separations and convective zone radius with respect to the Standard Solar Model. However, the required dipole moments are strongly excluded by direct detection experiments.

hep-ph↗

arXiv2009

Lattice Landau Gauge and Algebraic Geometry

Finding the global minimum of a multivariate function efficiently is a fundamental yet difficult problem in many branches of theoretical physics and chemistry. However, we observe that there are many physical systems for which the extremizing equations have polynomial-like non-linearity. This allows the use of Algebraic Geometry techniques to solve these equations completely. The global minimum can then straightforwardly be found by the second derivative test. As a warm-up example, here we study lattice Landau gauge for compact U(1) and propose two methods to solve the corresponding gauge-fixing equations. In a first step, we obtain all Gribov copies on one and two dimensional lattices. For simple 3x3 systems their number can already be of the order of thousands. We anticipate that the computational and numerical algebraic geometry methods employed have far-reaching implications beyond the simple but illustrating examples discussed here.

hep-lat↗

arXiv2008

Decontracted double BRST on the lattice

We present the Curci-Ferrari model on the lattice. In the massless case the topological interpretation of this model with its double BRST symmetry relates to the Neuberger 0/0 problem which we extend to include the ghost/anti-ghost symmetric formulation of the non-linear covariant Curci-Ferrari gauges on the lattice. The introduction of a Curci-Ferrari mass term, however, serves to regulate the 0/0 indeterminate form of physical observables observed by Neuberger. While such a mass m decontracts the double BRST/anti-BRST algebra, which is well-known to result in a loss of unitarity, observables can be meaningfully defined in the limit m to 0 via l'Hospital's rule. At finite m the topological nature of the partition function used as the gauge fixing device seems lost. We discuss the gauge parameter xi and mass m dependence of the model and show how both cancel when m = m(xi) is appropriately adjusted with xi.

hep-th↗