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T. N. Tomaras

Publications and source records attributed to T. N. Tomaras.

34 records · Page 2Linked to original sources
arXiv1999

Superconducting String Texture

We present a detailed analytical and numerical study of a novel type of static, superconducting, classically stable string texture in a renormalizable topologically trivial massive U(1) gauge model with one charged and one neutral scalar. An upper bound on the mass of the charged scalar as well as on the current that the string can carry are established. A preliminary unsuccesful search for stable solutions corresponding to large superconducting loops is also reported.

hep-ph↗
arXiv1999

New String Excitations in the Two-Higgs Standard Model

We establish the existence of a static, classically stable string solution in a region of parameters of the generic two-Higgs Standard Model. In an appropriate limit of parameters, the solution reduces to the well-known soliton of the O(3) non-linear sigma model.

hep-ph↗
arXiv1998

The Goldstone model static solutions on S^1

We study in a systematic way all static solutions of the Goldstone model in 1+1 dimension with a periodicity condition on the spatial coordinate. The solutions are presented in terms of the standard trigonometric functions and of Jacobi elliptic functions. Their stability analysis is carried out, and the complete list of classical stable quasi-topological solitons is given.

hep-th↗
arXiv1998

Perturbative Quantum Gravity And Newton's Law On A Flat Robertson-Walker Background

We derive the Feynman rules for the graviton in the presence of a flat Robertson-Walker background and give explicit expressions for the propagator in the physically interesting cases of inflation, radiation domination, and matter domination. The aforementioned background is generated by a scalar field source which should be taken to be dynamical. As an elementary application, we compute the corrections to the Newtonian gravitational force in the present matter dominated era and conclude -- as expected -- that they are negligible except for the largest scales.

gr-qc↗
arXiv1997

Maxwell--Chern-Simons gauged non-relativistic O(3) model with self-dual vortices

A non-relativistic version of the 2+1 dimensional gauged Chern-Simons O(3) sigma model, augmented by a Maxwell term, is presented and shown to support topologically stable static self-dual vortices. Exactly like their counterparts of the ungauged model, these vortices are shown to exhibit Hall behaviour in their dynamics.

hep-th↗
arXiv1997

Metastable Defects in the Generic 2HSM

A new kind of classically stable static solitons called metastable quasi-topological defects (MQTD) and a systematic method to search for them is presented, with examples from realistic particle physics models. They are characterized by a topological winding number, which is not absolutely conserved so that the MQTD may be converted to radiation by quantum mecanical tunneling. The two-Higgs standard model (2HSM) supports the existence of classically stable membranes for Higgs masses consistent with present day phenomenology and with perturbative unitarity, as well as with loop corrected MSSM. We also comment upon the possibility of metastable strings in the generic 2HSM.

hep-ph↗
arXiv1996

Metastable Defects in Generic Extensions of the Standard Model

The main features of the recently found classically stable quasi-topological membranes and strings in generic, topologically trivial and weakly coupled two-Higgs extensions of the standard model are briefly reviewed. A variety of localized solutions in the same model are also presented.

hep-ph↗
arXiv1996

On Spherically-Symmetric Solutions in the Two-Higgs Standard Model

We report the results of a numerical search for non-topological solitons in the two-Higgs standard model, characterized by the non-trivial winding, $π_3(S^3)$, of the relative phase of the two doublets. In a region of (weak-coupling) parameter space we identify a branch of winding solutions, which are lower in energy than the embedded standard sphaleron and deformed (bi)sphalerons. Contrary, however, to what happens in 2d toy models, these solutions remain unstable even for very large Higgs masses.

hep-ph↗
arXiv1996

Vortex Pairs in Charged Fluids

The motion of a vortex-(anti)vortex pair is studied numerically in the framework of a dynamical Ginzburg-Landau model, relevant to the description of a superconductor or of an idealized bosonic plasma. It is shown that up to a fine "cyclotron" internal motion, also studied in detail, two vortices brought together, rotate around each other, while a vortex and an antivortex move in formation parallel to each other. The velocities of the vortices in both cases are measured to be in remarkable agreement with recent theoretical predictions, down to intervortex distances as small as their characteristic diameter.

hep-th↗
arXiv1995

One-loop effective action around de Sitter space

The non-local one-loop contribution to the gravitational effective action around de Sitter space is computed using the background field method with pure trace external gravitational fields and it is shown to vanish. The calculation is performed in a generic covariant gauge and the result is verified to be gauge invariant.

hep-th↗
arXiv1995

Membranes in the two-Higgs standard model

We present some non-topological static wall solutions in two-Higgs extensions of the standard model. They are classically stable in a large region of parameter space, compatible with perturbative unitarity and with present phenomenological bounds.

hep-ph↗
arXiv1994

Higgs-Sector Solitons

We establish the existence of static, classically-stable, winding solitons in renormalizable three-dimensional gauge models, with topologically trivial target space and vacuum manifold. They are prototypes for possible analogous particle-like excitations in the higgs sector of the standard electroweak theory.

hep-ph↗
arXiv1994

Vortex Motion In Charged Fluids

A non-relativistic scalar field coupled minimally to electromagnetism supports in the presence of a homogeneous background electric charge density the existence of smooth, finite-energy topologically stable flux vortices. The static properties of such vortices are studied numerically in the context of a two parameter model describing this system as a special case. It is shown that the electrostatic and the mexican hat potential terms of the energy are each enough to ensure the existence of vortex solutions. The interaction potential of two minimal vortices is obtained for various values of the parameters. It is proven analytically that a free isolated vortex with topological charge $N\ne 0$ is spontaneously pinned, while in the presence of an external force it moves at a calculable speed and in a direction $(N/|N|) 90^0$ relative to it. In a homogeneous external current $\tilde {\bf J}$ the vortex velocity is $\bf V=-\tilde J$. Other theories with the same vortex behaviour are briefly discussed.

hep-th↗
arXiv1994

Ribbons Around Mexican Hats

We analyze quasi-topological solitons winding around a mexican-hat potential in two space-time dimensions. They are prototypes for a large number of physical excitations, including Skyrmions of the Higgs sector of the standard electroweak model, magnetic bubbles in thin ferromagnetic films, and strings in certain non-trivial backgrounds. We present explicit solutions, derive the conditions for classical stability, and show that contrary to the naive expectation these can be satisfied in the weak-coupling limit. In this limit we can calculate the soliton properties reliably, and estimate their lifetime semiclassically. We explain why gauge interactions destabilize these solitons, unless the scalar sector is extended.

hep-th↗