64,519 research outputs found
Experimental Signatures of Fermiophobic Higgs bosons
The most general Two Higgs Doublet Model potential without explicit CP
violation depends on 10 real independent parameters. Excluding spontaneous CP
violation results in two 7 parameter models. Although both models give rise to
5 scalar particles and 2 mixing angles, the resulting phenomenology of the
scalar sectors is different. If flavour changing neutral currents at tree level
are to be avoided, one has, in both cases, four alternative ways of introducing
the fermion couplings. In one of these models the mixing angle of the CP even
sector can be chosen in such a way that the fermion couplings to the lightest
scalar Higgs boson vanishes. At the same time it is possible to suppress the
fermion couplings to the charged and pseudo-scalar Higgs bosons by
appropriately choosing the mixing angle of the CP odd sector. We investigate
the phenomenology of both models in the fermiophobic limit and present the
different branching ratios for the decays of the scalar particles. We use the
present experimental results from the LEP collider to constrain the models.Comment: 23 pages, 18 figures included, newer experimental data include
Phonon instability in two-dimensional dipolar Bose-Einstein Condensates
The partially attractive character of the dipole-dipole interaction leads to
phonon instability in dipolar condensates, which is followed by collapse in
three-dimensional geometries. We show that the nature of this instability is
fundamentally different in two-dimensional condensates, due to the
dipole-induced stabilization of two-dimensional bright solitons. As a
consequence, a transient gas of attractive solitons is formed, and collapse may
be avoided. In the presence of an harmonic confinement, the instability leads
to transient pattern formation followed by the creation of stable
two-dimensional solitons. This dynamics should be observable in on-going
experiments, allowing for the creation of stable two-dimensional solitons for
the first time ever in quantum gases.Comment: 4 pages, 4 figure
Kinklike structures in scalar field theories: from one-field to two-field models
In this paper we study the possibility of constructing two-field models from
one-field models. The idea is to start with a given one-field model and use the
deformation procedure to generate another one-field model, and then couple the
two one-field models nontrivially, to get to a two-field model, together with
some explicit topological solutions. We show with several distinct examples
that the procedure works nicely and can be used generically.Comment: 8 pages; version to appear in Phys. Lett.
Massive "spin-2" theories in arbitrary dimensions
Here we show that in arbitrary dimensions there are two families of
second order Lagrangians describing massive "spin-2" particles via a
nonsymmetric rank-2 tensor. They differ from the usual Fierz-Pauli theory in
general. At zero mass one of the families is Weyl invariant. Such massless
theory has no particle content in and gives rise, via master action, to a
dual higher order (in derivatives) description of massive spin-2 particles in
where both the second and the fourth order terms are Weyl invariant,
contrary to the linearized New Massive Gravity. However, only the fourth order
term is invariant under arbitrary antisymmetric shifts. Consequently, the
antisymmetric part of the tensor propagates at large momentum as
instead of . So, the same kind of obstacle for the
renormalizability of the New Massive Gravity reappears in this nonsymmetric
higher order description of massive spin-2 particles.Comment: 11 pages, 0 figure
Faraday patterns in dipolar Bose-Einstein condensates
Faraday patterns can be induced in Bose-Einstein condensates by a periodic
modulation of the system nonlinearity. We show that these patterns are
remarkably different in dipolar gases with a roton-maxon excitation spectrum.
Whereas for non-dipolar gases the pattern size decreases monotonously with the
driving frequency, patterns in dipolar gases present, even for shallow roton
minima, a highly non trivial frequency dependence characterized by abrupt
pattern size transitions, which are especially pronounced when the dipolar
interaction is modulated. Faraday patterns constitute hence an optimal tool for
revealing the onset of the roton minimum, a major key feature of dipolar gases.Comment: 4 pages, 10 figure
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