arXiv subjects
Publications and source records attributed to Filipe Bonjour.
By considering full-field string solutions of the Abelian--Higgs model, we modify the model of a fluid of strings (which is composed of Nambu strings) to obtain a model for a ``fluid of vortices.'' With this model, and following closely Soleng's proposal of a fluid of strings as the source of a Milgrom-type correction to the Newton dynamics, we determine quantitatively the modified dynamics generated by a static, spherical fluid of vortices.
We examine the dynamics of a self-gravitating domain wall using the $λΦ^4$ model as a specific example. We find that the Nambu motion of the wall is quite generic and dominates the wall motion even in the presence of gravity. We calculate the corrections to this leading order motion, and estimate the effect of the inclusion of gravity on the dynamics of the wall. We then treat the case of a spherical gravitating thick wall as a particular example, solving the field equations and calculating the corrections to the Nambu motion analytically for this specific case. We find that the presence of gravity retards collapse in this case.
We investigate a self-gravitating thick domain wall for a $λΦ^4$ potential. The system of scalar and Einstein equations admits two types of non-trivial solutions: domain wall solutions and false vacuum-de Sitter solutions. The existence and stability of these solutions depends on the strength of the gravitational interaction of the scalar field, which is characterized by the number $ε$. For $ε\ll 1$, we find a domain wall solution by expanding the equations of motion around the flat spacetime kink. For ``large'' $ε$, we show analytically and numerically that only the de Sitter solution exists, and that there is a phase transition at some $ε_{\rm max}$ which separates the two kinds of solution. Finally, we comment on the existence of this phase transition and its relation to the topology of the domain wall spacetime.
We investigate the spacetime of a thick gravitating domain wall for a general potential $V(Φ)$. Using general analytical arguments we show that all nontrivial solutions fall into two categories: those interpretable as an isolated domain wall with a cosmological event horizon, and those which are pure false vacuum de Sitter solutions. Although this latter solution is always unstable to the field rolling coherently to its true vacuum, we show that there is an additional instability to wall formation if the scalar field does not couple too strongly to gravity. Using the $λΦ^4$ and sine-Gordon models as illustrative examples, we investigate the phase space of the gravitating domain wall in detail numerically, following the solutions from weak to strong gravity. We find excellent agreement with the analytic work. Then, we analyse the domain wall in the presence of a cosmological constant finding again the two kinds of solutions, wall and de Sitter, even in the presence of a negative cosmological constant.
It has been claimed that extreme black holes exhibit a phenomenon of flux expulsion for abelian Higgs vortices, irrespective of the relative width of the vortex to the black hole. Recent work by two of the authors showed a subtlety in the treatment of the event horizon, which cast doubt on this claim. We analyse in detail the vortex/extreme black hole system, showing that while flux expulsion can occur, it does not do so in all cases. We give analytic proofs for both expulsion and penetration of flux, in each case deriving a bound for that behaviour. We also present extensive numerical work backing up, and refining, these claims, and showing in detail how a vortex can end on a black hole in all situations. We also calculate the backreaction of the vortex on the geometry, and comment on the more general vortex-black hole system.
We examine the claim of Chamblin et. al. that extreme black holes cannot support abelian Higgs hair. We provide evidence that contradicts this claim and discuss reasons for this discrepancy.
We examine the leading order corrections to the Nambu effective action for the motion of a cosmic string, which appear at fourth order in the ratio of the width to radius of curvature of the string. We determine the numerical coefficients of these extrinsic curvature corrections, and derive the equations of motion of the worldsheet. Using these equations, we calculate the corrections to the motion of a collapsing loop, a travelling wave, and a helical breather. From the numerical coefficients we have calculated, we discuss whether the string motion can be labelled as `rigid' or `antirigid,' and hence whether cusp or kink formation might be suppressed or enhanced.