100 research outputs found
More On The Connection Between Planar Field Theory And String Theory
We continue work on the connection between world sheet representation of the
planar phi^3 theory and string formation. The present article, like the earlier
work, is based on the existence of a solitonic solution on the world sheet, and
on the zero mode fluctuations around this solution. The main advance made in
this paper is the removal of the cutoff and the transition to the continuum
limit on the world sheet. The result is an action for the modes whose energies
remain finite in this limit (light modes). The expansion of this action about a
dense background of graphs on the world sheet leads to the formation of a
string.Comment: 27 pages, 3 figure
Field Theory On The World Sheet: Improvements And Generalizations
This article is the continuation of a project of investigating planar phi^3
model in various dimensions. The idea is to reformulate them on the world
sheet, and then to apply the classical (meanfield) approximation, with two
goals: To show that the ground state of the model is a solitonic configuration
on the world sheet, and the quantum fluctuations around the soliton lead to the
formation of a transverse string. After a review of some of the earlier work,
we introduce and discuss several generalizations and new results. In 1+2
dimensions, a rigorous upper bound on the solitonic energy is established. A
phi^4 interaction is added to stabilize the original phi^3 model. In 1+3 and
1+5 dimensions, an improved treatment of the ultraviolet divergences is given.
And significantly, we show that our approximation scheme can be imbedded into a
systematic strong coupling expansion. Finally, the spectrum of quantum
fluctuations around the soliton confirms earlier results: In 1+2 and 1+3
dimensions, a transverse string is formed on the world sheet.Comment: 29 pages, 5 figures, several typos and eqs.(74) and (75) are
corrected, a comment added to section
Covariant And Local Field Theory On The World Sheet
In earlier work, using the light cone picture, a world sheet field theory
that sums planar phi^3 graphs was constructed and developed. Since this theory
is both non-local and not explicitly Lorentz invariant, it is desirable to have
a covariant and local alternative. In this paper, we construct such a covariant
and local world sheet theory, and show that it is equivalent to the original
non-covariant version.Comment: 22 pages,3 figures, typos and eqs.(11) and (63) are correcte
Status and Prospects of Top-Quark Physics
The top quark is the heaviest elementary particle observed to date. Its large
mass of about 173 GeV/c^2 makes the top quark act differently than other
elementary fermions, as it decays before it hadronises, passing its spin
information on to its decay products. In addition, the top quark plays an
important role in higher-order loop corrections to standard model processes,
which makes the top quark mass a crucial parameter for precision tests of the
electroweak theory. The top quark is also a powerful probe for new phenomena
beyond the standard model. During the time of discovery at the Tevatron in 1995
only a few properties of the top quark could be measured. In recent years,
since the start of Tevatron Run II, the field of top-quark physics has changed
and entered a precision era. This report summarises the latest measurements and
studies of top-quark properties and gives prospects for future measurements at
the Large Hadron Collider (LHC).Comment: 76 pages, 35 figures, submitted to Progress in Particle and Nuclear
Physic
Constrained BV Description of String Field Theory
In the conventional BV description of string field theory, the string field
Phi is split as Phi = Psi+Psi* where Psi includes all states with ghost number
less than or equal to G and describes the spacetime fields, and Psi* includes
all states with ghost number >G and describes the spacetime antifields. A new
approach is proposed here in which separate string fields Psi and Psi* of
unrestricted ghost number describe the spacetime fields and antifields. The
string antifield Psi* is constrained to satisfy Psi* = {\partial L}/{\partial(Q
Psi)} where L is the BV Lagrangian and Q is the worldsheet BRST operator. Dirac
antibrackets are defined using this constraint, and the resulting description
is equivalent to the conventional BV description for open and closed bosonic
string field theory. For open superstring field theory, this constrained BV
description is much simpler than the conventional BV description and allows the
BV action to be expressed in the same WZW-like form as the classical action.Comment: 21 pages harvmac te
Open superstring field theory I: gauge fixing, ghost structure, and propagator
The WZW form of open superstring field theory has linearized gauge invariances associated with the BRST operator Q and the zero mode η [subscript 0] of the picture minus-one fermionic superconformal ghost. We discuss gauge fixing of the free theory in a simple class of gauges using the Faddeev-Popov method. We find that the world-sheet ghost number of ghost and antighost string fields ranges over all integers, except one, and at any fixed ghost number, only a finite number of picture numbers appear. We calculate the propagators in a variety of gauges and determine the field-antifield content and the free master action in the Batalin-Vilkovisky formalism. Unlike the case of bosonic string field theory, the resulting master action is not simply related to the original gauge-invariant action by relaxing the constraint on the ghost and picture numbers.United States. Dept. of Energy (Cooperative rRsearch Agreement DE-FG02-05ER41360.
Thermal properties of a string bit model at large N
We study the finite temperature properties of a recently introduced string
bit model designed to capture some features of the emergent string in the
tensionless limit. The model consists of a pair of bosonic and fermionic bit
operators transforming in the adjoint representation of the color group SU(N).
Color confinement is not achieved as a dynamical effect, but instead is
enforced by an explicit singlet projection. At large N and finite temperature,
the model has a non trivial thermodynamics. In particular, there is a Hagedorn
type transition at a finite temperature where the string degrees of
freedom are liberated and the free energy gets a large contribution that plays the role of an order parameter. For , the low
temperature phase becomes unstable. In the new phase, the thermodynamically
favoured configurations are characterized by a non-trivial gapped density of
the SU(N) angles associated with the singlet projection. We present an accurate
algorithm for the determination of the density profile at . In
particular, we determine the gap endpoint at generic temperature and analytical
expansions valid near the Hagedorn transition as well as at high temperature.
The leading order corrections are characterized by non-trivial exponents that
are determined analytically and compared with explicit numerical calculations.Comment: 15 pages, 8 pdf figure
First order parent formulation for generic gauge field theories
We show how a generic gauge field theory described by a BRST differential can
systematically be reformulated as a first order parent system whose spacetime
part is determined by the de Rham differential. In the spirit of Vasiliev's
unfolded approach, this is done by extending the original space of fields so as
to include their derivatives as new independent fields together with associated
form fields. Through the inclusion of the antifield dependent part of the BRST
differential, the parent formulation can be used both for on and off-shell
formulations. For diffeomorphism invariant models, the parent formulation can
be reformulated as an AKSZ-type sigma model. Several examples, such as the
relativistic particle, parametrized theories, Yang-Mills theory, general
relativity and the two dimensional sigma model are worked out in details.Comment: 36 pages, additional sections and minor correction
Validity of Gauge-Fixing Conditions and the Structure of Propagators in Open Superstring Field Theory
We make a detailed analysis on validity of gauge-fixing conditions and the
structure of propagators in the Wess-Zumino-Witten-type open superstring field
theory. First, we generalize the gauge-fixing conditions considered in JHEP 03
(2012) 030 [arXiv:1201.1761] by the present author et al., and propose a large
class of conditions characterized by zero modes of world-sheet oscillators.
Then we demonstrate its validity: we prove that gauge degrees of freedom allow
us to impose the conditions, and that the conditions fix the gauges completely.
Moreover, we elucidate how the information about the gauge choices is reflected
in the structure of propagators. The results can be readily extended to the
case in which gauge-fixing conditions involve linear combinations of the
world-sheet oscillators, including nonzero modes. We investigate also such
extended gauges, which are the counterpart of linear -gauges in bosonic
string field theory, and obtain the corresponding propagators.Comment: LaTeX2e, 79 pages, 2 figures; v2: 80 pages, typos corrected, minor
changes; v3: Footnotes 15 and 16, and a few sentences have been added in
order to clarify the argument. typos corrected, published in JHEP; v4: typos
in equation (6.76) correcte
- …