16,926 research outputs found
Properties of the general NHDM. I. The orbit space
We study the scalar sector of the general N-Higgs-doublet model via geometric
constructions in the space of gauge orbits. We give a detailed description of
the shape of the orbit space both for general N and, in more detail, for N=3.
We also comment on remarkable analogies between NHDM and quantum information
theory.Comment: 27 pages, 2 figure
Group-theoretic restrictions on generation of CP-violation in multi-Higgs-doublet models
It has been known since decades that imposing a symmetry group G on the
scalar sector of multi-Higgs-doublet models has consequences for CP-violation.
In all examples of two- and three-Higgs-doublet models equipped with
symmetries, one observes the following intriguing property: if G prevents
explicit CP-violation (CPV), at least in the neutral Higgs sector, then it also
prevents spontaneous CPV, and if G allows explicit CPV, then it allows for
spontaneous CPV. One is led to conjecture that this is a general phenomenon. In
this paper, we prove this conjecture for any rephasing symmetry group G and any
number of doublets.Comment: 16 page
Higgs masses of the general 2HDM in the Minkowski-space formalism
We study the masses of the Higgs bosons in the most general two-Higgs-doublet
model in a basis-independent approach. We adapt the recently developed
Minkowski-space formalism to this problem and calculate traces of any power of
the mass-matrix in a compact and reparametrization-invariant form. Our results
can be used to gain insight into the dynamics of the scalar sector of the
general 2HDM.Comment: 14 pages, no figures; v2: reference added, misprints correcte
Orbital circularisation of white dwarfs and the formation of gravitational radiation sources in star clusters containing an intermediate mass black hole
(abbreviated) We consider how tight binaries consisting of a super-massive
black hole of mass and a white dwarf can be formed
in a globular cluster. We point out that a major fraction of white dwarfs
tidally captured by the black hole may be destroyed by tidal inflation during
ongoing circularisation, and the formation of tight binaries is inhibited.
However, some stars may survive being spun up to high rotation rates. Then the
energy loss through gravitational wave emission induced by tidally excited
pulsation modes and dissipation through non linear effects may compete with the
increase of pulsation energy due to dynamic tides. The semi-major axes of these
stars can be decreased below a 'critical' value where dynamic tides are not
effective because pulsation modes retain phase coherence between successive
pericentre passages. The rate of formation of such circularising stars is
estimated assuming that they can be modelled as polytropes and that
results of the tidal theory for slow rotators can be extrapolated to fast
rotators. We estimate the total capture rate as , where and
is the radius of influence of the black hole in units . We
find that the formation rate of tight pairs is approximately 10 times smaller
than the total capture rate. It is used to estimate the probability of
detection of gravitational waves coming from such tight binaries by LISA. We
conclude that LISA may detect such binaries provided that the fraction of
globular clusters with black holes in the mass range of interest is substantial
and that the dispersion velocity of the cluster stars near the radius of
influence of the black hole exceeds .Comment: accepted for publication in Astronomy and Astrophysics, minor
corrections in proof
Beyond basis invariants
Physical observables cannot depend on the basis one chooses to describe
fields. Therefore, all physically relevant properties of a model are, in
principle, expressible in terms of basis-invariant combinations of the
parameters. However, in many cases it becomes prohibitively difficult to
establish key physical features exclusively in terms of basis invariants. Here,
we advocate an alternative route in such cases: the formulation of
basis-invariant statements in terms of basis-covariant objects. We give several
examples where the basis-covariant path is superior to the traditional approach
in terms of basis invariants. In particular, this includes the formulation of
necessary and sufficient basis-invariant conditions for various physically
distinct forms of CP conservation in two- and three-Higgs-doublet models.Comment: 20 pages, no figure
On The Violation Of Marshall-Peierls Sign Rule In The Frustrated Heisenberg Antiferromagnet
We present a number of arguments in favor of the suggestion that the
Marshall-Peierls sign rule survives the frustration in the square-lattice
Heisenberg antiferromagnet with frustrating next-nearest-neighbor (diagonal)
bonds ( model) for relatively large values of the parameter
. Both the spin-wave analysis and the exact-diagonalization data
concerning the weight of Marshall states support the above suggestion.Comment: 8 pages, LaTex, 2 figurs on reques
Minkowski space structure of the Higgs potential in 2HDM: II. Minima, symmetries, and topology
We continue to explore the consequences of the recently discovered Minkowski
space structure of the Higgs potential in the two-Higgs-doublet model. Here, we
focus on the vacuum properties. The search for extrema of the Higgs potential
is reformulated in terms of 3-quadrics in the 3+1-dimensional Minkowski space.
We prove that 2HDM cannot have more than two local minima in the orbit space
and that a twice-degenerate minimum can arise only via spontaneous violation of
a discrete symmetry of the Higgs potential. Investigating topology of the
3-quadrics, we give concise criteria for existence of non-contractible paths in
the Higgs orbit space. We also study explicit symmetries of the Higgs
potential/lagrangian and their spontaneous violation from a wider perspective
than usual.Comment: 27 pages, 5 figure
The semileptonic decays of the B_c meson
We study the semileptonic transitions B_c to \eta_c, J/\psi, D, D^*, B, B^*,
B_s, B_s^* in the framework of a relativistic constituent quark model. We use
experimental data on leptonic J/\psi decay, lattice and QCD sum rule results on
leptonic B_c decay, and on radiative \eta_c transitions to adjust the quark
model parameters. We compute all form factors of the above semileptonic
B_c-transitions and give predictions for various semileptonic B_c decay modes
including their \tau-modes when they are kinematically accessible. The
implications of heavy quark symmetry for the semileptonic decays are discussed
and are shown to be manifest in our explicit relativistic quark model
calculation. A comparison of our results with the results of other calculations
is performed.Comment: 31 pages Latex (uses epsf, revtex). Section II expanded, typos
corrected. This version will appear in Phys. Rev.
- …