2,781 research outputs found
On D0 brane polarization by tidal forces
Gravitational tidal forces may induce polarization of D0 branes, in analogy
to the same effects arising in the context of constant background gauge fields.
Such phenomena can teach us about the correspondence between smooth curved
spacetime and its underlying non-commutative structure. However, unlike
polarization by gauge fields, the gravitational counterpart involves concerns
regarding the classical stability of the corresponding polarized states. In
this work, we study this issue with respect to the solutions presented in
hep-th/0010237 and find that they are classically unstable. The instability
however appears with intricate features with all but a few decay channels being
lifted. Through a detailed analysis, we then argue that these polarized states
may be expected to be long-lived in a regime where the string coupling is small
and the number of D0 branes is large.Comment: 22 pages, 7 figures, uses epsf; v2: citation added, report no
correcte
Holography with Ramond-Ramond fluxes
Starting from the non-linear sigma model of the IIB string in the light-cone
gauge, we analyze the role of RR fluxes in Holography. We find that the
worldsheet theory of states with only left or right moving modes does not see
the presence of RR fields threading a geometry. We use this significant
simplification to compute part of the strong coupling spectrum of the two
dimensional NCOS theory. We also reproduce the action of a closed string in a
PP-wave background using this general formalism; and we argue for various
strategies to find new systems where the closed string theory may be exactly
solvable.Comment: 22 pages, 1 figure; v2: clarifications added with regards to certain
missing terms in the action (which are not of relevance to the analysis and
conclusions
Comments on D branes and the renormalization group
We review the de Boer-Verlinde-Verlinde formalism for the renormalization
group in the context of Dp brane vacua. We comment on various aspects of the
dictionary between bulk and boundary and relate the discussion to the
Randall-Sundrum scenario. We find that the gravitational coupling for the
Randall-Sundrum gravity on the Dp brane worldvolume is proportional to the
c-function of the Yang-Mills theory. We compute the beta function and find the
expected uneventful flow prescribed by the classical dimension of the
Yang-Mills operator. Finally, we argue for a dynamical mechanism for
determining the cosmology on the brane.Comment: 23 pages, part of the NYGP lecture series, v2: a statement in
cosmology section corrected, citations added, typos corrected; v3: citation
added, a typo correcte
Hairy strings
Zero modes of the worldsheet spinors of a closed string can source higher
order moments of the bulk supergravity fields. In this work, we analyze various
configurations of closed strings focusing on the imprints of the quantized
spinor vevs onto the tails of bulk fields. We identify supersymmetric
arrangements for which all multipole charges vanish; while for others, we find
that one is left with NSNS and RR dipole and quadrupole moments. Our analysis
is exhaustive with respect to all the bosonic fields of the bulk and to all
higher order moments. We comment on the relevance of these results to entropy
computations of hairy black holes of a single charge or more, and to
open/closed string duality.Comment: 25 page
Holography, a covariant c-function, and the geometry of the renormalization group
We propose a covariant geometrical expression for the c-function for theories
which admit dual gravitational descriptions. We state a c-theorem with respect
to this quantity and prove it. We apply the expression to a class of
geometries, from domain walls in gauged supergravities, to extremal and near
extremal Dp branes, and the AdS Schwarzschild black hole. In all cases, we find
agreement with expectations.Comment: 20 pages, 1 figure; minor clarifications, a reference added, and a
few typos correcte
A new mechanism for non-locality from string theory: UV-IR quantum entanglement and its imprints on the CMB
Puff field theories (PFT) arise as the decoupling limits of D3 branes in a
Melvin universe and exhibit spatially non-local dynamics. Unlike other
realizations of non-locality in string theory, PFTs have full SO(3) rotational
symmetry. In this work, we analyze the strongly coupled regime of a PFT through
gravitational holography. We find a novel mechanism at the heart of the
phenomenon of non-locality: a quantum entanglement of UV and IR dynamics. In
the holographic bulk, this translates to an apparent horizon splitting the
space into two regions - with the UV completion of the PFT sitting at the
horizon. We unravel this intricate UV-IR setting and devise a prescription for
computing correlators that extends the original dictionary of holographic
renormalization group. We then implement a cosmological scenario where PFT
correlators set the initial conditions for primordial fluctuations. We compute
the associated power spectrum of the CMB and find that the scenario allows for
a distinct stringy signature.Comment: 40 pages, 15 figures; v2: citations added, minor figure corrections;
v3: minor changes, revised section 3.
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