716 research outputs found
The low-energy limit of AdS(3)/CFT2 and its TBA
We investigate low-energy string excitations in AdS3 Ă S3 Ă T4. When the worldsheet is decompactified, the theory has gapless modes whose spectrum at low energies is determined by massless relativistic integrable S matrices of the type introduced by Al. B. Zamolodchikov. The S matrices are non-trivial only for excitations with identical worldsheet chirality, indicating that the low-energy theory is a CFT2. We construct a Thermodynamic Bethe Ansatz (TBA) for these excitations and show how the massless modesâ wrapping effects may be incorporated into the AdS3 spectral problem. Using the TBA and its associated Y-system, we determine the central charge of the low-energy CFT2 to be c = 6 from calculating the vacuum energy for antiperiodic fermions â with the vacuum energy being zero for periodic fermions in agreement with a supersymmetric theory â and find the energies of some excited states
Light-cone gauge Hamiltonian for AdS_4 x CP^3 superstring
It is developed the phase-space formulation for the Type IIA superstring on
the AdS_4 x CP^3 background in the kappa-symmetry light-cone gauge for which
the light-like directions are taken from the D=3 Minkowski boundary of AdS_4.
After fixing bosonic light-cone gauge the superstring Hamiltonian is expressed
as a function of the transverse physical variables and in the quadratic
approximation corresponds to the light-cone gauge-fixed IIA superstring in flat
space.Comment: 12 pages, LaTeX; v2 minor improvements of the text, misprints
corrected, reference added; v3: missing terms in Eqs.(8),(53) and (56) adde
Strings in AdS_4 x CP^3: finite size spectrum vs. Bethe Ansatz
We compute the first curvature corrections to the spectrum of light-cone
gauge type IIA string theory that arise in the expansion of about a plane-wave limit. The resulting spectrum is shown to
match precisely, both in magnitude and degeneration that of the corresponding
solutions of the all-loop Gromov--Vieira Bethe Ansatz. The one-loop dispersion
relation correction is calculated for all the single oscillator states of the
theory, with the level matching condition lifted. It is shown to have all
logarithmic divergences cancelled and to leave only a finite exponentially
suppressed contribution, as shown earlier for light bosons. We argue that there
is no ambiguity in the choice of the regularization for the self-energy sum,
since the regularization applied is the only one preserving unitarity.
Interaction matrices in the full degenerate two-oscillator sector are
calculated and the spectrum of all two light magnon oscillators is completely
determined. The same finite-size corrections, at the order 1/J, where is
the length of the chain, in the two-magnon sector are calculated from the all
loop Bethe Ansatz. The corrections obtained by the two completely different
methods coincide up to the fourth order in . We
conjecture that the equivalence extends to all orders in and to
higher orders in 1/J.Comment: 32 pages. Published version; journal reference adde
Finite-gap equations for strings on AdS_3 x S^3 x T^4 with mixed 3-form flux
We study superstrings on AdS_3 x S^3 x T^4 supported by a combination of
Ramond-Ramond and Neveu-Schwarz-Neveu-Schwarz three form fluxes, and construct
a set of finite-gap equations that describe the classical string spectrum.
Using the recently proposed all-loop S-matrix we write down the all-loop Bethe
ansatz equations for the massive sector. In the thermodynamic limit the Bethe
ansatz reproduces the finite-gap equations. As part of this derivation we
propose expressions for the leading order dressing phases. These phases differ
from the well-known Arutyunov-Frolov-Staudacher phase that appears in the pure
Ramond-Ramond case. We also consider the one-loop quantization of the algebraic
curve and determine the one-loop corrections to the dressing phases. Finally we
consider some classical string solutions including finite size giant magnons
and circular strings.Comment: 44 pages, 3 figures. v2: references and a discussion about
perturbative results adde
Protected string spectrum in AdS(3)/CFT2 from worldsheet integrability
We derive the protected closed-string spectra of AdS3/CFT2 dual pairs with 16 supercharges at arbitrary values of the string tension and of the three-form fluxes. These follow immediately from the all-loop Bethe equations for the spectra of the integrable worldsheet theories. Further, representing the underlying integrable systems as spin chains, we find that their dynamics involves length-changing interactions and that protected states correspond to gapless excitations above the Berenstein-Maldacena-Nastase vacuum. In the case of AdS3 Ă S3 Ă T4 the degeneracies of such operators precisely match those of the dual CFT2 and the supergravity spectrum. On the other hand, we find that for AdS3 Ă S3 Ă S3 Ă S1 there are fewer protected states than previous supergravity calculations had suggested. In particular, protected states have the same su(2) charge with respect to the two three-spheres
Coordinate Bethe Ansatz for the String S-Matrix
We use the coordinate Bethe ansatz approach to derive the nested Bethe
equations corresponding to the recently found S-matrix for strings in AdS5 x
S5, compatible with centrally extended su(2|2) symmetry.Comment: 25 Pages, plain LaTeX, 4 Figures. Mostly added references, fixed
typo
Evaluating the Ability of Constructed Intertidal Eastern Oyster (\u3ci\u3eCrassostrea virginica\u3c/i\u3e) Reefs to Address Shoreline Erosion in South Carolina
The application of nature-based solutions to address shoreline erosion and the loss of salt marsh in coastal South Carolina has centered around the creation of intertidal oyster (Crassostrea virginica) reefs that act as natural breakwaters. The installation of such living shoreline materials often results in a rapid accumulation of fine sediments, followed by wild oyster recruitment to suitable materials, and then more gradually the growth of salt marshes (primarily Spartina alterniflora). Leveraging more than two decades of oyster reef restoration and living shorelines research at the South Carolina Department of Natural Resources, this study quantitatively assessed performance rates for both percent oyster cover and marsh protection in relation to reef age. Determining such rates will serve to inform the expectations of prospective adopters of living shorelines as to the timeframes of some of the biological processes, as measures of performance success, that will occur following material installation. Performance success was investigated in terms of recruitment of oysters to installed materials and the creation of new marsh habitat or protection of existing marsh from erosion. Reef age was an important determinant of reef âsuccessâ, with significant relationships between reef age and both performance success metrics. Percent oyster cover reached 40% by two years post-installation and 50% by four years post-installation, indicative of high rates of oyster recruitment. The relative marsh protection rate of living shorelines compared to unprotected reference plots was 0.4 m yr-1 Reef performance differed based on bank substrate firmness, bank width, shoreline morphology, and location relative to the Intracoastal Waterway (ICW). Firmer bank substrate was associated with greater percent oyster cover. Broader bank width was associated with greater marsh protection. Higher percent oyster cover measurements were observed on straight, natural shorelines and reefs located along the ICW. Reefs located on the ICW were also associated with greater marsh protection than reefs at non-ICW sites. Further, this study demonstrates that bagged oyster shell reefs are capable of providing shoreline protection services for more than a decade and can endure multiple intense storm events. The results of this study were also used to facilitate the implementation of new living shoreline regulations in coastal South Carolina in the hope of broadening adoption of this approach to addressing shoreline erosion and salt marsh habitat loss
On the worldsheet theory of the type IIA AdS(4) x CP(3) superstring
We perform a detailed study of the type IIA superstring in AdS(4) x CP(3).
After introducing suitable bosonic light-cone and fermionic kappa worldsheet
gauges we derive the pure boson and fermion SU(2|2) x U(1) covariant light-cone
Hamiltonian up to quartic order in fields.
As a first application of our derivation we calculate energy shifts for
string configurations in a closed fermionic subsector and successfully match
these with a set of light-cone Bethe equations. We then turn to investigate the
mismatch between the degrees of freedom of scattering states and oscillatory
string modes. Since only light string modes appear as fundamental Bethe roots
in the scattering theory, the physical role of the remaining massive
oscillators is rather unclear. By continuing a line of research initiated by
Zarembo, we shed light on this question by calculating quantum corrections for
the propagators of the bosonic massive fields. We show that, once loop
corrections are incorporated, the massive coordinates dissolve in a continuum
state of two light particles.Comment: 40 pages, 2 figures. v3: Minor clarifications made and reference list
updated. Published version
Simplifying superstring and D-brane actions in AdS(4) x CP(3) superbackground
By making an appropriate choice for gauge fixing kappa-symmetry we obtain a
relatively simple form of the actions for a D=11 superparticle in AdS(4) x
S(7)/Z_k, and for a D0-brane, fundamental string and D2-branes in the AdS(4) x
CP(3) superbackground. They can be used to study various problems of string
theory and the AdS4/CFT3 correspondence, especially in regions of the theory
which are not reachable by the OSp(6|4)/U(3) x SO(1,3) supercoset sigma-model.
In particular, we present a simple form of the gauge-fixed superstring action
in AdS(4) x CP(3) and briefly discuss issues of its T-dualization.Comment: 1+36 pages, v2,v3 clarifications and references adde
The Unequal World of Health Data
Peter Byass argues that less data are available on the health of the poor than of the rich, and discusses several alternative strategies to improve the representativeness of health data
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