44,027 research outputs found
2T-Physics 2001
The physics that is traditionally formulated in one--time-physics
(1T-physics) can also be formulated in two-time-physics (2T-physics). The
physical phenomena in 1T or 2T physics are not different, but the spacetime
formalism used to describe them is. The 2T description involves two extra
dimensions (one time and one space), is more symmetric, and makes manifest many
hidden features of 1T-physics. One such hidden feature is that families of
apparently different 1T-dynamical systems in d dimensions holographically
describe the same 2T system in d+2 dimensions. In 2T-physics there are two
timelike dimensions, but there is also a crucial gauge symmetry that thins out
spacetime, thus making 2T-physics effectively equivalent to 1T-physics. The
gauge symmetry is also responsible for ensuring causality and unitarity in a
spacetime with two timelike dimensions. What is gained through 2T-physics is a
unification of diverse 1T dynamics by making manifest hidden symmetries and
relationships among them. Such symmetries and relationships is the evidence for
the presence of the underlying higher dimensional spacetime structure.
2T-physics could be viewed as a device for gaining a better understanding of
1T-physics, but beyond this, 2T-physics offers new vistas in the search of the
unified theory while raising deep questions about the meaning of spacetime. In
these lectures, the recent developments in the powerful gauge field theory
formulation of 2T-physics will be described after a brief review of the results
obtained so far in the more intuitive worldline approach.Comment: 15 pages, LaTe
New Canonical Variables for d=11 Supergravity
A set of new canonical variables for supergravity is proposed which
renders the supersymmetry variations and the supersymmetry constraint
polynomial. The construction is based on the invariant
reformulation of supergravity given in previous work, and has some
similarities with Ashtekar's reformulation of Einstein's theory. The new
bosonic variables fuse the gravitational degrees of freedom with those of the
three-index photon in accordance with the hidden symmetries of the
dimensionally reduced theory. Although is not a symmetry of the theory,
the bosonic sector exhibits a remarkable structure, hinting at the
existence of a novel type of ``exceptional geometry''.Comment: 14 pages, LATE
Inflation, Symmetry, and B-Modes
We examine the role of using symmetry and effective field theory in
inflationary model building. We describe the standard formulation of starting
with an approximate shift symmetry for a scalar field, and then introducing
corrections systematically in order to maintain control over the inflationary
potential. We find that this leads to models in good agreement with recent
data. On the other hand, there are attempts in the literature to deviate from
this paradigm by invoking other symmetries and corrections. In particular: in a
suite of recent papers, several authors have made the claim that standard
Einstein gravity with a cosmological constant and a massless scalar carries
conformal symmetry. They further claim that such a theory carries another
hidden symmetry; a global SO(1,1) symmetry. By deforming around the global
SO(1,1) symmetry, they are able to produce a range of inflationary models with
asymptotically flat potentials, whose flatness is claimed to be protected by
these symmetries. These models tend to give rise to B-modes with small
amplitude. Here we explain that these authors are merely introducing a
redundancy into the description, not an actual conformal symmetry. Furthermore,
we explain that the only real (global) symmetry in these models is not at all
hidden, but is completely manifest when expressed in the Einstein frame; it is
in fact the shift symmetry of a scalar field. When analyzed systematically as
an effective field theory, deformations do not generally produce asymptotically
flat potentials and small B-modes, but other types of potentials with B-modes
of appreciable amplitude. Such simple models typically also produce the
observed red spectral index, Gaussian fluctuations, etc. In short: simple
models of inflation, organized by expanding around a shift symmetry, are in
excellent agreement with recent data.Comment: 9 pages in double column format. V2: Updated to coincide with version
published in Physics Letters
Extra s and s in Heterotic--String Derived Models
The ATLAS collaboration recently recorded possible excess in the di--boson
production at the di--boson invariant mass at around 2 TeV. Such an excess may
be produced if there exist additional and/or at that
scale. We survey the extra s and s that may arise from
semi--realistic heterotic string vacua in the free fermionic formulation in
seven distinct cases including: ; family universal
not in ; non--universal ; hidden
sector symmetries and kinetic mixing; left--right symmetric models;
Pati--Salam models; leptophobic and custodial symmetries. Each case has a
distinct signature associated with the extra symmetry breaking scale. In one of
the cases we explore the discovery potential at the LHC using resonant
leptoproduction. Existence of extra vector boson with the reported properties
will significantly constrain the space of allowed string vacua.Comment: 25 pages, 2 figures. Standard LaTeX. References added. Published
versio
Visible Effects of the Hidden Sector
The renormalization of operators responsible for soft supersymmetry breaking
is usually calculated by starting at some high scale and including only visible
sector interactions in the evolution equations, while ignoring hidden sector
interactions. Here we explain why this is correct only for the most trivial
structures in the hidden sector, and discuss possible implications. This
investigation was prompted by the idea of conformal sequestering. In that
framework hidden sector renormalizations by nearly conformal dynamics are
critical. In the original models of conformal sequestering it was necessary to
impose hidden sector flavor symmetries to achieve the sequestered form. We
present models which can evade this requirement and lead to no-scale or anomaly
mediated boundary conditions; but the necessary structures do not seem generic.
More generally, the ratios of scalar masses to gaugino masses, the -term,
the -term, -terms, and the gravitino mass can be significantly
affected.Comment: 23 pages, no figure
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