11,620 research outputs found
New Insights on Time and Quantum Gravity
According to Einstein, a universal time does not exist. But what if time is different than what we think of it? Cosmic Microvawe Background Radiation was accepted as a reference for a universal clock and a new time concept has been constructed. According to this new concept, time was tackled as two-dimensional having both a wavelength and a frequency. What our clocks measure is actually a derivation of the frequency of time. A relativistic time dilation actually corresponds to an increase in the wavelength of time. At the point where time wavelength and time frequency is equal, where light is positioned, quantum-world and macro- world are seperated. Gravity was redefined with respect to time and the new two dimensional time fabric of the universe was speculated to be the source of dark energy causing the universe to expand. According to this new point of view quantum realm and macro-world can be better understood. This new time concept provide a basis for our understanding of quantum gravity and provide the long-sought answers to well known problems of it. A prediction of the presented theory is that the universe will expand at various rates at different regions due to the fact that particular surroundings will create different gravities and cause a different gravity- time wavelength effect yielding various time delays for calculating this rate of expansion
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University Writing Cente
Massive Deformations of Type IIA Theory Within Double Field Theory
We obtain massive deformations of Type IIA supergravity theory through
duality twisted reductions of Double Field Theory (DFT) of massless Type II
strings. The mass deformation is induced through the reduction of the DFT of
the RR sector. Such reductions are determined by a twist element belonging to
, which is the duality group of the DFT of the RR sector. We
determine the form of the twists and give particular examples of twist
matrices, for which a massive deformation of Type IIA theory can be obtained.
In one of the cases, requirement of gauge invariance of the RR sector implies
that the dilaton field must pick up a linear dependence on one of the dual
coordinates. In another case, the choice of the twist matrix violates the weak
and the strong constraints explicitly in the internal doubled space.Comment: Section 4 (conclusion and outlook) expanded, published versio
Duality Twisted Reductions of Double Field Theory of Type II Strings
We study duality twisted reductions of the Double Field Theory (DFT) of the
RR sector of massless Type II theory, with twists belonging to the duality
group . We determine the action and the gauge algebra of the
resulting theory and determine the conditions for consistency. In doing this,
we work with the DFT action constructed by Hohm, Kwak and Zwiebach, which we
rewrite in terms of the Mukai pairing: a natural bilinear form on the space of
spinors, which is manifestly invariant. If the duality twist is
introduced via the element in the RR sector, then the NS-NS
sector should also be deformed via the duality twist , where
is the double covering homomorphism between and . We
show that the set of conditions required for the consistency of the reduction
of the NS-NS sector are also crucial for the consistency of the reduction of
the RR sector, owing to the fact that the Lie algebras of and
are isomorphic. In addition, requirement of gauge invariance imposes
an extra constraint on the fluxes that determine the deformations.Comment: chapter 4 revised and expanded, references added, published versio
Modeling and semigroup formulation of charge or current-controlled active constrained layer (ACL) beams; electrostatic, quasi-static, and fully-dynamic assumptions
A three-layer active constrained layer (ACL) beam model, consisting of a
piezoelectric elastic layer, a stiff layer, and a constrained viscoelastic
layer, is obtained for cantilevered boundary conditions by using the reduced
Rao-Nakra sandwich beam assumptions through a consistent variational approach.
The Rao-Nakra sandwich beam assumptions keeps the longitudinal and rotational
inertia terms. We consider electrostatic, quasi-static and fully dynamic
assumptions due to Maxwell's equations. For that reason, we first include all
magnetic effects for the piezoelectric layer. Two PDE models are obtained; one
for the charge-controlled case and one for the current-controlled case. These
two cases are considered separately since the underlying control operators are
very different in nature. For both cases, the semigroup formulations are
presented, and the corresponding Cauchy problems are shown to be well- posed in
the natural energy space.Comment: 2 figure
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