59,166 research outputs found
't Hooft and Wilson loop ratios in the QCD plasma
The spatial 't Hooft loop measuring the electric flux and the spatial
Wilsonloop measuring the magnetic flux are analyzed in hot SU(N) gauge theory.
Both display area laws. On one hand the tension of the 't Hooft loop is
perturbatively calculable, in the same sense as the pressure. We show that the
O(g^3) contribution is absent. The ratio of multi-charged 't Hooft loops have a
remarkably simple dependence on the charge, true up to, but not including,
O(g^4). This dependence follows also from a simple model of free screened
colour charges. On the other hand the surface tension of the Wilsonloop is
non-perturbative. But in a model of screened free monopoles at very high
temperature the known area law follows. The density of these monopoles starts
to contribute to O(g^6) to the pressure. The ratio of the multicharged Wilson
loops is calculable and identical to that of the 't Hooft loops.Comment: 28 pages, 8 figure
Non-Abelian Monopoles as the Origin of Dark Matter
We suggest that dark matter may be partially constituted by a dilute 't
Hooft-Polyakov monopoles gas. We reach this conclusion by using the
Georgi-Glashow model coupled to a dual kinetic mixing term where is the electromagnetic field and the 't Hooft tensor.
We show that these monopoles carry both (Maxwell) electric and (Georgi-Glashow)
magnetic charges and the electric charge quantization condition is modified in
terms of a dimensionless real parameter. This parameter could be determined
from milli-charged particle experiments.Comment: 5 pp, no figure
Quantum 't Hooft operators and S-duality in N=4 super Yang-Mills
We provide a quantum path integral definition of an 't Hooft loop operator,
which inserts a pointlike monopole in a four dimensional gauge theory. We
explicitly compute the expectation value of the circular 't Hooft operators in
N=4 super Yang-Mills with arbitrary gauge group G up to next to leading order
in perturbation theory. We also compute in the strong coupling expansion the
expectation value of the circular Wilson loop operators. The result of the
computation of an 't Hooft loop operator in the weak coupling expansion exactly
reproduces the strong coupling result of the conjectured dual Wilson loop
operator under the action of S-duality. This paper demonstrates - for the first
time - that correlation functions in N=4 super Yang-Mills admit the action of
S-duality.Comment: 38 pages; v2: references added, typos fixe
Low-lying meson spectrum of large strongly coupled lattice QCD
We compute the low energy mass spectrum of lattice QCD in the large
limit. Expanding around a gauge-invariant ground state, which spontaneously
breaks the discrete chiral symmetry, we derive an improved strong-coupling
expansion and evaluate, for any value of , the masses of the low-lying
states in the unflavored meson spectrum. We then take the 't Hooft limit by
rescaling ; the 't Hooft limit is smooth and no arbitrary
parameters are needed. We find, already at the fourth order of the strong
coupling perturbation theory, a very good agreement between the results of our
lattice computation and the known continuum values.Comment: 43 pages, 1 figure. Minor corrections. One reference added in section
The Intermediate Coupling Regime in the AdS/CFT Correspondence
The correspondence between the 't Hooft limit of N=4 super Yang-Mills theory
and tree-level IIB superstring theory on AdS(5)xS(5) in a Ramond-Ramond
background at values of lambda=g^2 N ranging from infinity to zero is examined
in the context of unitarity. A squaring relation for the imaginary part of the
holographic scattering of identical string fields in the two-particle channels
is found, and a mismatch between weak and strong 't Hooft coupling is pointed
out within the correspondence. Several interpretations and implications are
proposed.Comment: 10 pages, LaTeX, reference adde
TransPlanckian Particles and the Quantization of Time
Trans-Planckian particles are elementary particles accelerated such that
their energies surpass the Planck value. There are several reasons to believe
that trans-Planckian particles do not represent independent degrees of freedom
in Hilbert space, but they are controlled by the cis-Planckian particles. A way
to learn more about the mechanisms at work here, is to study black hole
horizons, starting from the scattering matrix Ansatz.
By compactifying one of the three physical spacial dimensions, the scattering
matrix Ansatz can be exploited more efficiently than before. The algebra of
operators on a black hole horizon allows for a few distinct representations. It
is found that this horizon can be seen as being built up from string bits with
unit lengths, each of which being described by a representation of the SO(2,1)
Lorentz group. We then demonstrate how the holographic principle works for this
case, by constructing the operators corresponding to a field in space-time. The
parameter t turns out to be quantized in Planckian units, divided by the period
R of the compactified dimension.Comment: 12 pages plain tex, 1 figur
Positivity of hexagon perturbation theory
The hexagon-form-factor program was proposed as a way to compute three- and
higher-point correlation functions in super-symmetric
Yang-Mills theory and in the dual AdSS superstring theory, by
exploiting the integrability of the theory in the 't Hooft limit. This approach
is reminiscent of the asymptotic Bethe ansatz in that it applies to a
large-volume expansion. Finite-volume corrections can be incorporated through
L\"uscher-like formulae, though the systematics of this expansion is largely
unexplored so far. Strikingly, finite-volume corrections may feature negative
powers of the 't Hooft coupling in the small- expansion, potentially
leading to a breakdown of the formalism. In this work we show that the
finite-volume perturbation theory for the hexagon is positive and thereby
compatible with the weak-coupling expansion for arbitrary -point functions.Comment: v2: misprints corrected, further details on physical magnons adde
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