222 research outputs found
Confinement from spontaneous breaking of scale symmetry
We show that one can obtain naturally the confinement of static charges from
the spontaneous symmetry breaking of scale invariance in a gauge theory. At the
classical level a confining force is obtained and at the quantum level, using a
gauge invariant but path-dependent variables formalism, the Cornell confining
potential is explicitly obtained. Our procedure answers completely to the
requirements by 't Hooft for ''perturbative confinement''.Comment: 6 page
Dynamical Couplings, Dynamical Vacuum Energy and Confinement/Deconfinement from R^2-Gravity
We study within Palatini formalism an f(R)-gravity with f(R)= R + \alpha R^2
interacting with a dilaton and a special kind of nonlinear gauge field system
containing a square-root of the standard Maxwell term, which is known to
produce confinement in flat space-time. Reformulating the model in the physical
Einstein frame we find scalar field effective potential with a flat region
where the confinement dynamics disappears, while in other regions it remains
intact. The effective gauge couplings as well as the induced cosmological
constant become dynamical. In particular, a conventional Maxwell kinetic term
for the gauge field is dynamically generated even if absent in the original
theory. We find few interesting classes of explicit solutions: (i)
asymptotically (anti-)de Sitter black holes of non-standard type with
additional confining vacuum electric potential even for the electrically
neutral ones; (ii) non-standard Reissner-Nordstroem black holes with additional
constant vacuum electric field and having non-flat-spacetime "hedgehog"
asymptotics; (iii) generalized Levi-Civitta-Bertotti-Robinson "tube-like"
space-times.Comment: 16 page
Asymptotically de Sitter and anti-de Sitter Black Holes with Confining Electric Potential
We study gravity interacting with a special kind of QCD-inspired nonlinear
gauge field system which earlier was shown to yield confinement-type effective
potential (the "Cornell potential") between charged fermions ("quarks") in flat
space-time. We find new static spherically symmetric solutions generalizing the
usual Reissner-Nordstroem-de-Sitter and Reissner-Nordstroem-anti-de-Sitter
black holes with the following additional properties: (i) appearance of a
constant radial electric field (in addition to the Coulomb one); (ii) novel
mechanism of {\em dynamical generation} of cosmological constant through the
non-Maxwell gauge field dynamics; (iii) appearance of confining-type effective
potential in charged test particle dynamics in the above black hole
backgrounds.Comment: 9 pages, v2 12 pages, many additional clarifying remarks, references
added, v3 minor typos corrected, to appear in Physics Letters B, v4 missing
line in Eqs.(10) and missing constant factors in Eqs.(12),(17) inserted,
acknowledgement added, results unchange
Inflation and Transition to a Slowly Accelerating Phase from S.S.B. of Scale Invariance
We consider the effects of adding a scale invariant term to the
action of the scale invariant model (SIM) studied previously by one of us
(E.I.G., Mod. Phys. Lett. A14, 1043 (1999)). The SIM belongs to the general
class of theories, where an integration measure independent of the metric is
introduced. To implement scale invariance (S.I.), a dilaton field is
introduced. The integration of the equations of motion associated with the new
measure gives rise to the spontaneous symmetry breaking (S.S.B) of S.I.. After
S.S.B. of S.I. in the model with the term, it is found that a non
trivial potential for the dilaton is generated. This potential contains two
flat regions: one associated with the Planck scale and with an inflationary
phase, while the other flat region is associated to a very small vacuum energy
(V.E.) and is associated to the present slowly accelerated phase of the
universe (S.A.PH). The smallness of the V.E. in the S.A.PH. is understood
through the see saw mechanism introduced in S.I.M.Comment: 22 pages, latex, three figures now in separate file
Fully Explorable Horned Particles Hiding Charge
The charge-hiding effect by a horned particle, which was studied for the case
where gravity/gauge-field system is self-consistently interacting with a
charged lightlike brane (LLB) as a matter source, is now studied for the case
of a time like brane. From the demand that no surfaces of infinite coordinate
time redshift (horizons) appear in the problem we are lead now to a completly
explorable horned particle space for traveller that goes through the horned
particle (as was the case for the LLB) but now also in addition to this, the
horned region is fully visible to a static external observer. This requires
negative surface energy density for the shell sitting at the throat. We study a
gauge field subsystem which is of a special non-linear form containing a
square-root of the Maxwell term and which previously has been shown to produce
a QCD-like confining gauge field dynamics in flat space-time. The condition of
finite energy of the system or asymptotic flatness on one side of the horned
particle implies that the charged object sitting at the throat expels all the
flux it produces into the other side of the horned particle, which turns out to
be of a "tube-like" nature. An outside observer in the asymptotically flat
universe detects, therefore, apparently neutral object. The hiding of the
electric flux behind the tube-like region of a horned particle is the only
possible way that a truly charged particle can still be of finite energy, in a
theory that in flat space describes confinement. This points to the physical
relevance of such solutions, even though there is the need of negative energy
density at the throat of the horned particle, which can be of quantum
mechanical origin.Comment: The new version has been accepted for publication in Classical and
Quantum Gravity. Title changed to "Fully Explorable Horned Particles Hiding
Charge". Horned Particles terminology is used now instead of "wormholes" to
dscribe the solutions here. arXiv admin note: text overlap with
arXiv:1108.373
Scalar-Tensor Gravity in Two 3-brane System
We derive the low-energy effective action of four-dimensional gravity in the
Randall-Sundrum scenario in which two 3-branes of opposite tension reside in a
five-dimensional spacetime. The dimensional reduction with the Ansatz for the
radion field by Charmousis et al., which solves five-dimensional linearized
field equations, results in a class of scalar-tensor gravity theories. In the
limit of vanishing radion fluctuations, the effective action reduces to the
Brans-Dicke gravity in accord with the results of Garriga and Tanaka:
Brans-Dicke gravity with the corresponding Brans-Dicke parameter (for positive tension brane) and (for negative
tension brane). In general the gravity induced a brane belongs to a class of
scalar-tensor gravity with the Brans-Dicke parameter which is a function of the
interval and the radion. In particular, gravity on a positive tension brane
contains an attractor mechanism toward the Einstein gravity.Comment: 8 pages, discussion expanded, references adde
Extra Dimensional Curvature Supression of the Effective Four Dimensional Vacuum Energy Density
Considering a very large number of extra dimensions, ,
we show that in the effective four dimensional picture, to leading order in
, both the cosmological constant in dimensions and the curvature of
the extra dimensions (curved as spheres) give the same type of contributions.
Furthermore in this limit, the extra dimensional curvature naturally supress
the effect of a positive Cosmological Constant, so that the resulting effective
potential governing the vacuum energy in the effective picture has a
leading 1/N dependence (i.e. vanishing in the large limit). We can
understand qualitatively this effect in a heuristic picture, by thinking that
all dimensions, both visible and extra have an equal sharing of the curvature
caused by , in this case when increasing the overall number of
dimensions by adding extra dimensions, then if is large, the visible
dimensions do not have to curve too much, hence a small four dimensional vacuum
energy follows. In the large picture the potential can be also stabilized
by a small (i.e. vanishing at large ) expectaction value of a four index
field strength.Comment: 8 page
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