2,907 research outputs found
A Way to Dynamically Overcome the Cosmological Constant Problem
The Cosmological Constant problem can be solved once we require that the full
standard Einstein Hilbert lagrangian, gravity plus matter, is multiplied by a
total derivative. We analyze such a picture writing the total derivative as the
covariant gradient of a new vector field (b_mu). The dynamics of this b_mu
field can play a key role in the explanation of the present cosmological
acceleration of the Universe.Comment: 5 page
New limits on the mass of neutral Higgses in General Models
In general electroweak models with weakly coupled (and otherwise arbitrary)
Higgs sector there always exists in the spectrum a scalar state with mass
controlled by the electroweak scale. A new and simple recipe to compute an
analytical tree-level upper bound on the mass of this light scalar is given. We
compare this new bound with similar ones existing in the literature and show
how to extract extra information on heavier neutral scalars in the spectrum
from the interplay of independent bounds. Production of these states at future
colliders is addressed and the implications for the decoupling limit in which
only one Higgs is expected to remain light are discussed.Comment: 14 pages, LaTe
Thermodynamics of perfect fluids from scalar field theory
The low-energy dynamics of relativistic continuous media is given by a
shift-symmetric effective theory of four scalar fields. These scalars describe
the embedding in spacetime of the medium and play the role of St\"uckelberg
fields for spontaneously broken spatial and time translations. Perfect fluids
are selected imposing a stronger symmetry group or reducing the field content
to a single scalar. We explore the relation between the field theory
description of perfect fluids to thermodynamics. By drawing the correspondence
between the allowed operators at leading order in derivatives and the
thermodynamic variables, we find that a complete thermodynamic picture requires
the four Stuckelberg fields. We show that thermodynamic stability plus the
null-energy condition imply dynamical stability. We also argue that a
consistent thermodynamic interpretation is not possible if any of the shift
symmetries is explicitly broken.Comment: 25 pages, 1 figure. Few typos corrected. Accepted for publication in
PR
Enhanced Electroweak Corrections to Inclusive Boson Fusion Processes at the TeV Scale
Electroweak radiative corrections with double-log enhancements occur in
inclusive observables at the TeV scale because of a lack of compensation of
virtual corrections with real emission due to the nonabelian (weak isospin)
charges of the accelerator beams. Here we evaluate such Bloch-Nordsieck
violating corrections in the case of initial longitudinal bosons, which is
experimentally provided by boson fusion processes, and is related to the
Goldstone-Higgs sector. All four states of this sector are involved in the
group structure of the corrections, and cause in particular a novel double log
effect due to hypercharge mixing in the longitudinal states. We study both the
light- and the heavy-Higgs cases, and we analyze the symmetry breaking pattern
of the corrections. The latter turn out to be pretty large, in the 5-10 %
range, and show an interesting Higgs mass dependence, even for processes
without Higgs boson in the final state.Comment: 15 pages, 6 figure
- …