755 research outputs found
Nonlocal multi-trace sources and bulk entanglement in holographic conformal field theories
We consider CFT states defined by adding nonlocal multi-trace sources to the
Euclidean path integral defining the vacuum state. For holographic theories, we
argue that these states correspond to states in the gravitational theory with a
good semiclassical description but with a more general structure of bulk
entanglement than states defined from single-trace sources. We show that at
leading order in large N, the entanglement entropies for any such state are
precisely the same as those of another state defined by appropriate
single-trace effective sources; thus, if the leading order entanglement
entropies are geometrical for the single-trace states of a CFT, they are
geometrical for all the multi-trace states as well. Next, we consider the
perturbative calculation of 1/N corrections to the CFT entanglement entropies,
demonstrating that these show qualitatively different features, including
non-analyticity in the sources and/or divergences in the naive perturbative
expansion. These features are consistent with the expectation that the 1/N
corrections include contributions from bulk entanglement on the gravity side.
Finally, we investigate the dynamical constraints on the bulk geometry and the
quantum state of the bulk fields which must be satisfied so that the entropies
can be reproduced via the quantum-corrected Ryu-Takayanagi formula.Comment: 60 pages + appendices, 7 figures; v2: minor additions, published
versio
The Gravity Dual of a Density Matrix
For a state in a quantum field theory on some spacetime, we can associate a
density matrix to any subset of a given spacelike slice by tracing out the
remaining degrees of freedom. In the context of the AdS/CFT correspondence, if
the original state has a dual bulk spacetime with a good classical description,
it is natural to ask how much information about the bulk spacetime is carried
by the density matrix for such a subset of field theory degrees of freedom. In
this note, we provide several constraints on the largest region that can be
fully reconstructed, and discuss specific proposals for the geometric
construction of this dual region.Comment: 19 pages, LaTeX, 8 figures, v2: footnote and reference adde
Generally Covariant Actions for Multiple D-branes
We develop a formalism that allows us to write actions for multiple D-branes
with manifest general covariance. While the matrix coordinates of the D-branes
have a complicated transformation law under coordinate transformations, we find
that these may be promoted to (redundant) matrix fields on the transverse space
with a simple covariant transformation law. Using these fields, we define a
covariant distribution function (a matrix generalization of the delta function
which describes the location of a single brane). The final actions take the
form of an integral over the curved space of a scalar single-trace action built
from the covariant matrix fields, tensors involving the metric, and the
covariant distribution function. For diagonal matrices, the integral localizes
to the positions of the individual branes, giving N copies of the single-brane
action.Comment: 34 pages, LaTeX. v2: comments and refs adde
Minimal subtraction and the Callan-Symanzik equation
The usual proof of renormalizability using the Callan-Symanzik equation makes
explicit use of normalization conditions. It is shown that demanding that the
renormalization group functions take the form required for minimal subtraction
allows one to prove renormalizability using the Callan-Symanzik equation,
without imposing normalization conditions. Scalar field theory and quantum
electrodynamics are treated.Comment: 6 pages, plain Te
Review of the Phenomenology of Noncommutative Geometry
We present a pedagogical review of particle physics models that are based on
the noncommutativity of space-time, , with specific attention to the phenomenology these models predict in
particle experiments either in existence or under development. We summarize
results obtained for high energy scattering such as would occur for example in
a future linear collider with , as well as low
energy experiments such as those pertaining to elementary electric dipole
moments and other \cpviolng observables, and finally comment on the status of
phenomenological work in cosmology and extra dimensions.Comment: updated, references added, corrected typo
On the Problem of Multiple M2 Branes
A simplified version of 3d BL theory is considered, which allows any number N
of M2 branes in d=11. The underlying 3-algebra structure is provided by
degenerate U(N) Nambu bracket [X,Y,Z] = tr(X) [Y,Z] + tr(Y) [Z,X] + tr(Z)
[X,Y], the corresponding f^{abcd} is not totally antisymmetric and extended
supersymmetry of the action remains to be checked. All the fields, including
auxiliary non-propagating gauge fields, are in adjoint representation of SU(N)
and the only remnant of 3-algebra structure is an octuple of gauge singlets,
acquiring vacuum expectation value in transition to D2 branes in d=10.Comment: 12 page
M2-branes on M-folds
We argue that the moduli space for the Bagger-Lambert A_4 theory at level k
is (R^8 \times R^8)/D_{2k}, where D_{2k} is the dihedral group of order 4k. We
conjecture that the theory describes two M2-branes on a Z_{2k} ``M-fold'', in
which a geometrical action of Z_{2k} is combined with an action on the branes.
For k=1, this arises as the strong coupling limit of two D2-branes on an O2^-
orientifold, whose worldvolume theory is the maximally supersymmetric SO(4)
gauge theory. Finally, in an appropriate large-k limit we show that one
recovers compactified M-theory and the M2-branes reduce to D2-branes.Comment: 16 pages, LaTeX, v2: typos corrected, included appendices on
Chern-Simons level quantization and monopole charge quantizatio
S-duality in AdS/CFT magnetohydrodynamics
We study the nonlinear hydrodynamics of a 2+1 dimensional charged conformal
fluid subject to slowly varying external electric and magnetic fields.
Following recent work on deriving nonlinear hydrodynamics from gravity, we
demonstrate how long wavelength perturbations of the AdS dyonic black brane
solution of 4D supergravity are governed by equations equivalent to fluid
dynamics equations in the boundary theory. We investigate the implications of
-duality for our system, and derive restrictions imposed on the transport
coefficients of a generic fluid invariant under the S operation. We also expand
on our earlier work and determine a new set of previously undetermined
transport coefficients for the conformal fluid with an AdS gravity dual. Quite
surprisingly, we discover that half of the transport coefficients allowed by
symmetry vanish in the holographic fluid at linear order in the hydrodynamic
expansion.Comment: 25 page
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