2,635 research outputs found
Identification of indirect new physics effects at e^+e^- colliders: the large extra dimensions case
We discuss indirect manifestations of graviton exchange, predicted by large
extra dimensions, in fermion-pair production at a high-energy e^+e^- collider.
By means of specifically defined asymmetries among integrated angular
distributions, the graviton exchange signal can be cleanly distinguished from
the effects of either vector-vector contact interactions or heavy scalar
exchanges. The role of initial electron and positron beams polarization is also
discussed. The method is applied to a quantitative assessment of the
sensitivity to the mass cut-off parameter M_H of the KK graviton tower in the
ADD scenario, and of the potential identification reach of this mechanism
obtainable at the currently planned Linear Collider.Comment: 21 pages, 11 figure
Triumphalism in the Gospels
While the words ‘triumph', ‘triumphal' and ‘triumphant' are words with a long history, the expression ‘triumphalism' is a modern invention. It seems to have started its career when first Bishop de Smedt of Belgium and later other speakers used it in their speeches in the early sessions of the Second Vatican Council. Through the innumerable articles and books about the Council it became widely known and became a current expression in the terminology of writers on religious themes. The speed and extent of its success showed that it pointed to the existence of an acute problem in the life of the churches. This problem was clearly stated in a contribution to the council's debate on the nature of the Church by Bishop Laszlo of Eisenstad
Quantum Gravity as a Dissipative Deterministic System
It is argued that the so-called holographic principle will obstruct attempts
to produce physically realistic models for the unification of general
relativity with quantum mechanics, unless determinism in the latter is
restored. The notion of time in GR is so different from the usual one in
elementary particle physics that we believe that certain versions of hidden
variable theories can -- and must -- be revived. A completely natural procedure
is proposed, in which the dissipation of information plays an essential role.
Unlike earlier attempts, it allows us to use strictly continuous and
differentiable classical field theories as a starting point (although discrete
variables, leading to fermionic degrees of freedom, are also welcome), and we
show how an effective Hilbert space of quantum states naturally emerges when
one attempts to describe the solutions statistically. Our theory removes some
of the mysteries of the holographic principle; apparently non-local features
are to be expected when the quantum degrees of freedom of the world are
projected onto a lower-dimensional black hole horizon. Various examples and
models illustrate the points we wish to make, notably a model showing that
massless, non interacting neutrinos are deterministic.Comment: 20 pages plain TeX, 2 figures PostScript. Added some further
explanations, and the definitions of `beable' and `changeable'. A minor error
correcte
Quantum Mechanics of a Point Particle in 2+1 Dimensional Gravity
We study the phase space structure and the quantization of a pointlike
particle in 2+1 dimensional gravity. By adding boundary terms to the first
order Einstein Hilbert action, and removing all redundant gauge degrees of
freedom, we arrive at a reduced action for a gravitating particle in 2+1
dimensions, which is invariant under Lorentz transformations and a group of
generalized translations. The momentum space of the particle turns out to be
the group manifold SL(2). Its position coordinates have non-vanishing Poisson
brackets, resulting in a non-commutative quantum spacetime. We use the
representation theory of SL(2) to investigate its structure. We find a
discretization of time, and some semi-discrete structure of space. An
uncertainty relation forbids a fully localized particle. The quantum dynamics
is described by a discretized Klein Gordon equation.Comment: 58 pages, 3 eps figures, presentation of the classical theory
improve
Color Bosonization, Chiral Parametrization of Gluonic Field and QCD Effective Action
We develop a color bosonization approach to treatment of QCD gauge field
(''gluons'') at low energies in order to derive an effective color action of
QCD taking into account the quark chiral anomaly in the case of SU(2) color..
We have found that there exists such a region in the chiral sector of color
space, where a gauge field coincides with of chirally rotated vector field,
while an induced axial vector field disappears. In this region, the unit color
vector of chiral field plays a defining role, and a gauge field is parametrized
in terms of chiral parameters, so that no additional degrees of freedom are
introduced by the chiral field. A QCD gauge field decomposition in color
bosonization is a sum of a chirally rotated gauge field and an induced
axial-vector field expressed in terms of gluonic variables. An induced
axial-vector field defines the chiral color anomaly and an effective color
action of QCD. This action admits existence of a gauge invariant d=2 condensate
of induced axial-vector field and mass.Comment: 13 pages, LaTe
Quantum Topological Invariants, Gravitational Instantons and the Topological Embedding
Certain topological invariants of the moduli space of gravitational
instantons are defined and studied. Several amplitudes of two and four
dimensional topological gravity are computed. A notion of puncture in four
dimensions, that is particularly meaningful in the class of Weyl instantons, is
introduced. The topological embedding, a theoretical framework for constructing
physical amplitudes that are well-defined order by order in perturbation theory
around instantons, is explicitly applied to the computation of the correlation
functions of Dirac fermions in a punctured gravitational background, as well as
to the most general QED and QCD amplitude. Various alternatives are worked out,
discussed and compared. The quantum background affects the propagation by
generating a certain effective ``quantum'' metric. The topological embedding
could represent a new chapter of quantum field theory.Comment: LaTeX, 18 pages, no figur
Distinguishing New Physics Scenarios at a Linear Collider with Polarized Beams
Numerous non-standard dynamics are described by contact-like effective
interactions that can manifest themselves through deviations of the cross
sections from the Standard Model predictions. If one such deviation were
observed, one should try to identify to a given confidence level the actual
source among the possible non-standard interactions that in principle can
explain it. We here estimate the potential identification reach on different
New Physics effective interactions, obtainable from the angular distributions
of lepton pair production processes at the planned International Linear
Collider with polarized beams. The models discussed are the interactions based
on gravity in large and in TeV^{-1} extra dimensions and the
compositeness-inspired four-fermion contact interactions. The availability of
both beams polarized in many cases plays an essential role in enhancing the
identification sensitivity.Comment: 21 pages, LaTex, 11 figures. One author was missing from the previous
version. The authors list has been completed, no other change
Hamiltonian structure and quantization of 2+1 dimensional gravity coupled to particles
It is shown that the reduced particle dynamics of 2+1 dimensional gravity in
the maximally slicing gauge has hamiltonian form. This is proved directly for
the two body problem and for the three body problem by using the Garnier
equations for isomonodromic transformations. For a number of particles greater
than three the existence of the hamiltonian is shown to be a consequence of a
conjecture by Polyakov which connects the auxiliary parameters of the fuchsian
differential equation which solves the SU(1,1) Riemann-Hilbert problem, to the
Liouville action of the conformal factor which describes the space-metric. We
give the exact diffeomorphism which transforms the expression of the spinning
cone geometry in the Deser, Jackiw, 't Hooft gauge to the maximally slicing
gauge. It is explicitly shown that the boundary term in the action, written in
hamiltonian form gives the hamiltonian for the reduced particle dynamics. The
quantum mechanical translation of the two particle hamiltonian gives rise to
the logarithm of the Laplace-Beltrami operator on a cone whose angular deficit
is given by the total energy of the system irrespective of the masses of the
particles thus proving at the quantum level a conjecture by 't Hooft on the two
particle dynamics. The quantum mechanical Green's function for the two body
problem is given.Comment: 34 pages LaTe
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