114 research outputs found
Cosmology and the Higgs mechanism
It is noted that spontaneous symmetry treaking implies
a finite cosmological term in the Einstein equation for
gravity. The present theories of weak and e.m. interactions
disagree violently with the experimental limit on such a
term unless an ad-hoc counter curvature is introduced
QCD recursion relations from the largest time equation
We show how by reassembling the tree level gluon Feynman diagrams in a
convenient gauge, space-cone, we can explicitly derive the BCFW recursion
relations. Moreover, the proof of the gluon recursion relations hinges on an
identity in momentum space which we show to be nothing but the Fourier
transform of the largest time equation. Our approach lends itself to natural
generalizations to include massive scalars and even fermions.Comment: 18 pages, 2 figures, minor changes to Sect.
Quantum gauge models without classical Higgs mechanism
We examine the status of massive gauge theories, such as those usually
obtained by spontaneous symmetry breakdown, from the viewpoint of causal
(Epstein-Glaser) renormalization. The BRS formulation of gauge invariance in
this framework, starting from canonical quantization of massive (as well as
massless) vector bosons as fundamental entities, and proceeding perturbatively,
allows one to rederive the reductive group symmetry of interactions, the need
for scalar fields in gauge theory, and the covariant derivative. Thus the
presence of higgs particles is explained without recourse to a
Higgs(-Englert-Brout-Guralnik-Hagen-Kibble) mechanism. Along the way, we dispel
doubts about the compatibility of causal gauge invariance with grand unified
theories.Comment: 20 pages in two-column EPJC format, shortened version accepted for
publication. For more details, consult version
The Character of Z-pole Data Constraints on Standard Model Parameters
Despite the impressive precision of the Z-pole measurements made at LEP and
SLC, the allowed region for the principle Standard Model parameters responsible
for radiative corrections (the mass of the Higgs, the mass of the top and
alpha(Mz)) is still large enough to encompass significant non-linearities. The
nature of the experimental constraints therefore depends in an interesting way
on the "accidental" relationships among the various measurements. In
particular, the fact that the Z-pole measurements favor values of the Higgs
mass excluded by direct searches leads us to examine the effects of external
Higgsstrahlung, a process ignored by the usual precision electroweak
calculations.Comment: 9 pages, 6 figures, REVTeX format; added reference in section IV;
added paragraph on widths and a few cosmetic changes to correspond to
published versio
A nondiagrammatic calculation of the Rho parameter from heavy fermions
A simple nondiagrammatic evaluation of the nondecoupling effect of heavy
fermions on the Veltman's Rho parameter is presented in detail. This
calculation is based on the path integral approach, the electroweak chiral
Lagrangian formalism, and the Schwinger proper time method.Comment: 11 page
Generalized Weinberg Sum Rules in Deconstructed QCD
Recently, Son and Stephanov have considered an "open moose" as a possible
dual model of a QCD-like theory of chiral symmetry breaking. In this note we
demonstrate that although the Weinberg sum rules are satisfied in any such
model, the relevant sums converge very slowly and in a manner unlike QCD.
Further, we show that such a model satisfies a set of generalized sum rules.
These sum rules can be understood by looking at the operator product expansion
for the correlation function of chiral currents, and correspond to the absence
of low-dimension gauge-invariant chiral symmetry breaking condensates. These
results imply that, regardless of the couplings and F-constants chosen, the
open moose is not the dual of any QCD-like theory of chiral symmetry breaking.
We also show that the generalized sum rules can be "solved", leading to a
compact expression for the difference of vector- and axial-current correlation
functions. This expression allows for a simple formula for the S parameter
(L_10), which implies that S is always positive and of order one in any
(unitary) open linear moose model. Therefore the S parameter is positive and
order one in any "Higgsless model" based on the continuum limit of a linear
moose regardless of the warping or position-dependent gauge-coupling chosen.Comment: 12 pages, 5 eps figures; reference to overlapping work adde
Unitarity-Cuts and Berry's Phase
Elaborating on the observation that two-particle unitarity-cuts of scattering
amplitudes can be computed by applying Stokes' Theorem, we relate the Optical
Theorem to the Berry Phase, showing how the imaginary part of arbitrary
one-loop Feynman amplitudes can be interpreted as the flux of a complex 2-form.Comment: 3 pages, 1 figur
Physical Unitarity for Massive Non-abelian Gauge Theories in the Landau Gauge: Stueckelberg and Higgs
We discuss the problem of unitarity for Yang-Mills theory in the Landau gauge
with a mass term a la Stueckelberg. We assume that the theory
(non-renormalizable) makes sense in some subtraction scheme (in particular the
Slavnov-Taylor identities should be respected!) and we devote the paper to the
study of the space of the unphysical modes. We find that the theory is unitary
only under the hypothesis that the 1-PI two-point function of the vector mesons
has no poles (at p^2=0). This normalization condition might be rather crucial
in the very definition of the theory. With all these provisos the theory is
unitary. The proof of unitarity is given both in a form that allows a direct
transcription in terms of Feynman amplitudes (cutting rules) and in the
operatorial form. The same arguments and conclusions apply verbatim to the case
of non-abelian gauge theories where the mass of the vector meson is generated
via Higgs mechanism. To the best of our knowledge, there is no mention in the
literature on the necessary condition implied by physical unitarity.Comment: References added. 22 pages. Final version to appear in the journa
On (non-Hermitian) Lagrangeans in (particle) physics and their dynamical generation
On the basis of a new method to derive the effective action the
nonperturbative concept of "dynamical generation" is explained. A non-trivial,
non-Hermitian and PT-symmetric solution for Wightman's scalar field theory in
four dimensions is dynamically generated, rehabilitating Symanzik's precarious
phi**4-theory with a negative quartic coupling constant as a candidate for an
asymptotically free theory of strong interactions. Finally it is shown making
use of dynamically generation that a Symanzik-like field theory with scalar
confinement for the theory of strong interactions can be even suggested by
experiment.Comment: 12 pages, no figures, accepted for publication in Czech.J.Phys.,
revised with respect to obvious typo
Equivalence Theorem and Probing the Electroweak Symmetry Breaking Sector
We examine the Lorentz non-invariance ambiguity in longitudinal weak-boson
scatterings and the precise conditions for the validity of the Equivalence
Theorem (ET). {\it Safe} Lorentz frames for applying the ET are defined, and
the intrinsic connection between the longitudinal weak-boson scatterings and
probing the symmetry breaking sector is analyzed. A universal precise
formulation of the ET is presented for both the Standard Model and the Chiral
Lagrangian formulated Electro-Weak Theories. It is shown that in electroweak
theories with strongly interacting symmetry breaking sector, the longitudinal
weak-boson scattering amplitude {\it under proper conditions} can be replaced
by the corresponding Goldstone-boson scattering amplitude in which all the
internal weak-boson lines and fermion loops are ignored.Comment: 20 pages, in LaTeX, to appear in Phys. Rev. D (1995). A few minor
corrections were made to clarify our viewpoint of the Equivalence Theorem and
compare our conclusion with those in the literatur
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