47 research outputs found
On the ABJM four-point amplitude at three loops and BDS exponentiation
We study the three-loop four-point amplitude in ABJM theory. We determine the
dual conformal invariant integrals with highest number of propagators and fix
their coefficients by two-particle cuts. Evaluating such a combination of
integrals in dimensional regularization we provide evidence for exponentiation
of the amplitude, including the finite terms. In addition we show that the
three-loop amplitude can be expressed in terms of classical polylogarithms of
uniform degree of transcendentality.Comment: 31 pages, 4 figure
Hairy black holes sourced by a conformally coupled scalar field in D dimensions
There exist well-known no-hair theorems forbidding the existence of hairy
black hole solutions in general relativity coupled to a scalar conformal field
theory in asymptotically flat space. Even in the presence of cosmological
constant, where no-hair theorems can usually be circumvented and black holes
with conformal scalar hair were shown to exist in dimensions three and four,
no-go results were reported for D>4. In this paper we prove that these
obstructions can be evaded and we answer in the affirmative a question that
remained open: Whether hairy black holes do exist in general relativity sourced
by a conformally coupled scalar field in arbitrary dimensions. We find the
analytic black hole solution in arbitrary dimension D>4, which exhibits a
backreacting scalar hair that is regular everywhere outside and on the horizon.
The metric asymptotes to (Anti-)de Sitter spacetime at large distance and
admits spherical horizon as well as horizon of a different topology. We also
find analytic solutions when higher-curvature corrections O(R^n) of arbitrary
order n are included in the gravity action.Comment: 5 pages, no figures. V2: minor changes. Published versio
Light-like Wilson loops in ABJM and maximal transcendentality
We revisit the computation of the two-loop light-like tetragonal Wilson loop
for three dimensional pure Chern-Simons and N=6 Chern-Simons-matter theory,
within dimensional regularization with dimensional reduction scheme. Our
examination shows that, contrary to prior belief, the result respects maximal
transcendentality as is the case of the four-point scattering amplitude of the
theory. Remarkably, the corrected result matches exactly the scattering
amplitude both in the divergent and in the finite parts, constants included.Comment: 11 page
The 1/2 BPS Wilson loop in ABJ(M) at two loops: The details
We compute the expectation value of the 1/2 BPS circular Wilson loop operator
in ABJ(M) theory at two loops in perturbation theory. Our result turns out to
be in exact agreement with the weak coupling limit of the prediction coming
from localization, including finite N contributions associated to non-planar
diagrams. It also confirms the identification of the correct framing factor
that connects framing-zero and framing-one expressions, previously proposed.
The evaluation of the 1/2 BPS operator is made technically difficult in
comparison with other observables of ABJ(M) theory by the appearance of
integrals involving the coupling between fermions and gauge fields, which are
absent for instance in the 1/6 BPS case. We describe in detail how to
analytically solve these integrals in dimensional regularization with
dimensional reduction (DRED). By suitably performing the physical limit to
three dimensions we clarify the role played by short distance divergences on
the final result and the mechanism of their cancellation.Comment: 54 pages, 2 figure
Probing Wilson loops in Chern-Simons-matter theories at weak coupling
For three-dimensional super Chern-Simons-matter theories
associated to necklace quivers , we study at quantum level the two kinds of 1/2 BPS Wilson loop operators
recently introduced in arXiv:1506.07614. We perform a two-loop evaluation and
find the same result for the two kinds of operators, so moving to higher loops
a possible quantum uplift of the classical degeneracy. We also compute the 1/4
BPS bosonic Wilson loop and discuss the quantum version of the cohomological
equivalence between fermionic and bosonic Wilson loops. We compare the
perturbative result with the Matrix Model prediction and find perfect matching,
after identification and remotion of a suitable framing factor. Finally, we
discuss the potential appearance of three-loop contributions that might break
the classical degeneracy and briefly analyse possible implications on the BPS
nature of these operators.Comment: 7 pages, 2 figure
BPS Wilson loops and Bremsstrahlung function in ABJ(M): a two loop analysis
We study a family of circular BPS Wilson loops in N=6 super
Chern-Simons-matter theories, generalizing the usual 1/2-BPS circle. The scalar
and fermionic couplings depend on two deformation parameters and these
operators can be considered as the ABJ(M) counterpart of the DGRT latitudes
defined in N=4 SYM. We perform a complete two-loop analysis of their vacuum
expectation value, discuss the framing dependence and propose a general
relation with cohomologically equivalent bosonic operators. We make an all-loop
proposal for computing the Bremsstrahlung function associated to the 1/2-BPS
cusp in terms of these generalized Wilson loops. When applied to our two-loop
result it reproduces the known expression. Finally, we comment on the
generalization of this proposal to the bosonic 1/6-BPS case.Comment: 46 pages, 6 figures; references adde
The quantum 1/2 BPS Wilson loop in Chern-Simons-matter theories
In three dimensional Chern-Simons-matter theories two
independent fermionic Wilson loop operators can be defined, which preserve half
of the supersymmetry charges and are cohomologically equivalent at classical
level. We compute their three-loop expectation value in a convenient color
sector and prove that the degeneracy is uplifted by quantum corrections. We
expand the matrix model prediction in the same regime and by comparison we
conclude that the quantum 1/2 BPS Wilson loop is the average of the two
operators. We provide an all-loop argument to support this claim at any order.
As a by-product, we identify the localization result at three loops as a
correction to the framing factor induced by matter interactions. Finally, we
comment on the quantum properties of the non-1/2 BPS Wilson loop operator
defined as the difference of the two fermionic ones.Comment: 22 pages + appendixes, 4 figures, 1 Tabl
Causality in 3D Massive Gravity Theories
We study the constraints coming from local causality requirement in various
dimensional dynamical theories of gravity. In topologically massive
gravity, with a single parity non-invariant massive degree of freedom, and in
new massive gravity, with two massive spin- degrees of freedom, causality
and unitarity are compatible with each other and both require the Newton's
constant to be negative. In their extensions, such as the Born-Infeld gravity
and the minimal massive gravity the situation is similar and quite different
from their higher dimensional counterparts, such as quadratic (e.g.,
Einstein-Gauss-Bonnet) or cubic theories, where causality and unitarity are in
conflict. We study the problem both in asymptotically flat and asymptotically
anti-de Sitter spaces.Comment: This version has significant improvements: causality discussion of
all the well-known gravity theories in flat space is extended to the AdS
space, references added, 29 pages, latest version matches the published on