30,882 research outputs found
The SU(2) X U(1) Electroweak Model based on the Nonlinearly Realized Gauge Group
The electroweak model is formulated on the nonlinearly realized gauge group
SU(2) X U(1). This implies that in perturbation theory no Higgs field is
present. The paper provides the effective action at the tree level, the Slavnov
Taylor identity (necessary for the proof of unitarity), the local functional
equation (used for the control of the amplitudes involving the Goldstone
bosons) and the subtraction procedure (nonstandard, since the theory is not
power-counting renormalizable). Particular attention is devoted to the number
of independent parameters relevant for the vector mesons; in fact there is the
possibility of introducing two mass parameters. With this choice the relation
between the ratio of the intermediate vector meson masses and the Weinberg
angle depends on an extra free parameter. We briefly outline a method for
dealing with \gamma_5 in dimensional regularization. The model is formulated in
the Landau gauge for sake of simplicity and conciseness: the QED Ward identity
has a simple and intriguing form.Comment: 19 pages, final version published by Int. J. Mod. Phys. A, some typos
corrected in eqs.(1) and (41). The errors have a pure editing origin.
Therefore they do not affect the content of the pape
A Symmetric Approach to the Massive Nonlinear Sigma Model
In the present paper we extend to the massive case the procedure of
divergences subtraction, previously introduced for the massless nonlinear sigma
model (D=4). Perturbative expansion in the number of loops is successfully
constructed. The resulting theory depends on the Spontaneous Symmetry Breaking
parameter v, on the mass m and on the radiative correction parameter \Lambda.
Fermions are not considered in the present work. SU(2) X SU(2) is the group
used.Comment: 20 page
Features controlling the early stages of creep deformation of Waspaloy
A model has been presented for describing primary and second stage creep. General equations were derived for the amount and time of primary creep. It was shown how the model can be used to extrapolate creep data. Applicability of the model was demonstrated for Waspaloy with gamma prime particle sizes from 75 - 1000 A creep tested in the temperature range 1000 - 1400 F (538 - 760 C). Equations were developed showing the dependence of creep parameters on dislocation mechanism, gamma prime volume fraction and size
Distributed bounded-error state estimation for partitioned systems based on practical robust positive invariance
We propose a partition-based state estimator for linear discrete-time systems
composed by coupled subsystems affected by bounded disturbances. The
architecture is distributed in the sense that each subsystem is equipped with a
local state estimator that exploits suitable pieces of information from parent
subsystems. Moreover, differently from methods based on moving horizon
estimation, our approach does not require the on-line solution to optimization
problems. Our state-estimation scheme, that is based on the notion of practical
robust positive invariance developed in Rakovic 2011, also guarantees
satisfaction of constraints on local estimation errors and it can be updated
with a limited computational effort when subsystems are added or removed
Path-integral over non-linearly realized groups and Hierarchy solutions
The technical problem of deriving the full Green functions of the elementary
pion fields of the nonlinear sigma model in terms of ancestor amplitudes
involving only the flat connection and the nonlinear sigma model constraint is
a very complex task. In this paper we solve this problem by integrating, order
by order in the perturbative loop expansion, the local functional equation
derived from the invariance of the SU(2) Haar measure under local left
multiplication. This yields the perturbative definition of the path-integral
over the non-linearly realized SU(2) group.Comment: 26 page
Of Higgs, Unitarity and other Questions
On the verge of conclusive checks on the Standard Model by the LHC, we
discuss some of the basic assumptions. The reason for this analysis stems from
a recent proposal of an Electroweak Model based on a nonlinearly realized gauge
group SU(2) X U(1), where, in the perturbative approximation, there is no Higgs
boson. The model enjoys the Slavnov-Taylor identities and therefore the
perturbative unitarity. On the other hand, it is commonly believed that the
existence of the Higgs boson is entangled with the property of unitarity, when
high energy processes are considered. The argument is based mostly on the
Froissart bound and on the Equivalence Theorem. In this talk we briefly review
some of our objections on the validity of such arguments. Some open questions
are pointed out, in particular on the limit of zero mass for the vector mesons
and on the fate of the longitudinal polarizations.Comment: 23 pages, 1 figure, presented by Ruggero Ferrari at the International
Conference "Gauge Fields. Yesterday, Today, Tomorrow" in honor of A.A.
Slavnov. Moscow, January 19-24 201
Machine learning-based Raman amplifier design
A multi-layer neural network is employed to learn the mapping between Raman
gain profile and pump powers and wavelengths. The learned model predicts with
high-accuracy, low-latency and low-complexity the pumping setup for any gain
profile.Comment: conferenc
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