26,369 research outputs found
A Strategy for a Vanishing Cosmological Constant in the Presence of Scale Invariance Breaking
Recent work has shown that complex quantum field theory emerges as a
statistical mechanical approximation to an underlying noncommutative operator
dynamics based on a total trace action. In this dynamics, scale invariance of
the trace action becomes the statement , with the operator stress energy tensor, and with the trace over the
underlying Hilbert space. We show that this condition implies the vanishing of
the cosmological constant and vacuum energy in the emergent quantum field
theory. However, since the scale invariance condition does not require the
operator to vanish, the spontaneous breakdown of scale
invariance is still permitted.Comment: Second award in the Gravity Research Foundation Essay Competition for
1997; to appear in General Relativity and Gravitation. Plain Tex, no figure
Quantum Fermion Hair
It is shown that the Dirac operator in the background of a magnetic
%Reissner-Nordstr\"om black hole and a Euclidean vortex possesses normalizable
zero modes in theories containing superconducting cosmic strings. One
consequence of these zero modes is the presence of a fermion condensate around
magnetically charged black holes which violates global quantum numbers.Comment: 16pp (harvmac (l)) and 2 figs.(not included
Compact extra-dimensions as solution to the strong CP problem
We show that the strong CP problem can, in principle, be solved dynamically
by adding extra-dimensions with compact topology. To this aim we consider a toy
model for QCD, which contains a vacuum angle and a strong CP like problem. We
further consider a higher dimensional theory, which has a trivial vacuum
structure and which reproduces the perturbative properties of the toy model in
the low-energy limit. In the weak coupling regime, where our computations are
valid, we show that the vacuum structure of the low-energy action is still
trivial and the strong CP problem is solved. No axion-like particle occur in
this setup and therefore it is not ruled out by astrophysical bounds.Comment: Discussion adde
Effects of an extra U(1) axial condensate on the strong decays of pseudoscalar mesons
We consider a scenario (supported by some lattice results) in which a
U(1)-breaking condensate survives across the chiral transition in QCD. This
scenario has important consequences for the pseudoscalar-meson sector, which
can be studied using an effective Lagrangian model. In particular, generalizing
the results obtained in two previous papers, where the effects on the radiative
decays eta,eta' --> gamma gamma were studied, in this paper we study the
effects of the U(1) chiral condensate on the strong decays of the "light"
pseudoscalar mesons, i.e., eta,eta' --> 3pi^0; eta,eta' --> pi^+ pi^- pi^0;
eta' --> eta pi^0 pi^0; eta' --> eta pi^+ pi^-; and also on the strong decays
of an exotic ("heavy") SU(3)-singlet pseudoscalar state eta_X, predicted by the
model.Comment: One misprint in Eq. (2.10) has been eliminated; Eqs. (B.8) and (B.9)
in Appendix B have been corrected; 46 pages, 1 tabl
Relation between Tunneling and Particle Production in Vacuum Decay
The field-theoretical description of quantum fluctuations on the background
of a tunneling field is revisited in the case of a functional
Schrodinger approach. We apply this method in the case when quantum
fluctuations are coupled to the field through a mass-squared term,
which is 'time-dependent' since we include the dynamics of . The
resulting mode functions of the fluctuation field, which determine the quantum
state after tunneling, display a previously unseen resonance effect when their
mode number is comparable to the curvature scale of the bubble. A detailed
analysis of the relation between the excitations of the field about the true
vacuum (interpreted as particle creation) and the phase shift coming from
tunneling is presented.Comment: 20 pages, 4 figures, submitted to PR
Two-Dimensional Bosonization from Variable Shifts in the Path Integral
A method to perform bosonization of a fermionic theory in (1+1) dimensions in
a path integral framework is developed. The method relies exclusively on the
path integral property of allowing variable shifts, and does not depend on the
explicit form of Greens functions. Two examples, the Schwinger model and the
massless Thirring model, are worked out.Comment: 4 page
Field Decomposition and the Ground State Structure of SU(2) Yang-Mills Theory
We compute the effective potential of SU(2) Yang-Mills theory using the
background field method and the Faddeev-Niemi decomposition of the gauge
fields. In particular, we find that the potential will depend on the values of
two scalar fields in the decomposition and that its structure will give rise to
a symmetry breaking.Comment: 8 pages, 1 figure. Typos corrected and title change
Classical solution of the wave equation
The classical limit of wave quantum mechanics is analyzed. It is shown that
the general requirements of continuity and finiteness to the solution
, where and
is the reduced classical action of the physical system, result in the
asymptote of the exact solution and general quantization condition for ,
which yields the exact eigenvalues of the system.Comment: 8 Pages, 10 Refs, LaTe
Gravitational Thermodynamics of Space-time Foam in One-loop Approximation
We show from one-loop quantum gravity and statistical thermodynamics that the
thermodynamics of quantum foam in flat space-time and Schwarzschild space-time
is exactly the same as that of Hawking-Unruh radiation in thermal equilibrium.
This means we show unambiguously that Hawking-Unruh thermal radiation should
contain thermal gravitons or the contribution of quantum space-time foam. As a
by-product, we give also the quantum gravity correction in one-loop
approximation to the classical black hole thermodynamics.Comment: 7 pages, revte
No supercritical supercurvature mode conjecture in one-bubble open inflation
In the path integral approach to false vacuum decay with the effect of
gravity, there is an unsolved problem, called the negative mode problem. We
show that the appearance of a supercritical supercurvature mode in the
one-bubble open inflation scenario is equivalent to the existence of a negative
mode around the Euclidean bounce solution. Supercritical supercurvature modes
are those whose mode functions diverge exponentially for large spatial radius
on the time constant hypersurface of the open universe. Then we propose a
conjecture that there should be ``no supercritical supercurvature mode''. For a
class of models that contains a wide variety of tunneling potentials, this
conjecture is shown to be correct.Comment: 11 pages, 3 postscript figures, tarred, gzipped. submitted to Phys.
Rev. D1
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