1,416 research outputs found
Triangle Anomalies from Einstein Manifolds
The triangle anomalies in conformal field theory, which can be used to
determine the central charge a, correspond to the Chern-Simons couplings of
gauge fields in AdS under the gauge/gravity correspondence. We present a simple
geometrical formula for the Chern-Simons couplings in the case of type IIB
supergravity compactified on a five-dimensional Einstein manifold X. When X is
a circle bundle over del Pezzo surfaces or a toric Sasaki-Einstein manifold, we
show that the gravity result is in perfect agreement with the corresponding
quiver gauge theory. Our analysis reveals an interesting connection with the
condensation of giant gravitons or dibaryon operators which effectively induces
a rolling among Sasaki-Einstein vacua.Comment: 30 pages, 5 figures; published versio
Nilpotent orbits and codimension-two defects of 6d N=(2,0) theories
We study the local properties of a class of codimension-2 defects of the 6d
N=(2,0) theories of type J=A,D,E labeled by nilpotent orbits of a Lie algebra
\mathfrak{g}, where \mathfrak{g} is determined by J and the outer-automorphism
twist around the defect. This class is a natural generalisation of the defects
of the 6d theory of type SU(N) labeled by a Young diagram with N boxes. For any
of these defects, we determine its contribution to the dimension of the Higgs
branch, to the Coulomb branch operators and their scaling dimensions, to the 4d
central charges a and c, and to the flavour central charge k.Comment: 57 pages, LaTeX2
Liouville/Toda central charges from M5-branes
We show that the central charge of the Liouville and ADE Toda theories can be
reproduced by equivariantly integrating the anomaly eight-form of the
corresponding six-dimensional N=(0,2) theories, which describe the low-energy
dynamics of M5-branes.Comment: 9 page
27/32
We show that when an N=2 SCFT flows to an N=1 SCFT via giving a mass to the
adjoint chiral superfield in a vector multiplet with marginal coupling, the
central charges a and c of the N=2 theory are related to those of the N=1
theory by a universal linear transformation. In the large N limit, this
relationship implies that the central charges obey a_IR/a_UV=c_IR/c_UV=27/32.
This gives a physical explanation to many examples of this number found in the
literature, and also suggests the existence of a flow between some theories not
previously thought to be connected.Comment: 3 pages. v2: references added, minor typos correcte
The gravity duals of SO/USp superconformal quivers
We study the gravity duals of SO/USp superconformal quiver gauge theories
realized by M5-branes wrapping on a Riemann surface ("G-curve") together with a
Z_2-quotient. When the G-curve has no punctures, the gravity solutions are
classified by the genus g of the G-curve and the torsion part of the four-form
flux G_4. We also find that there is an interesting relation between anomaly
contributions from two mysterious theories: T_{SO(2N)} theory with SO(2N)^3
flavor symmetry and \tilde{T}_{SO(2N)} theory with SO(2N) x USp(2N-2)^2 flavor
symmetry. The dual gravity solutions for various SO/USp-type tails are also
studied.Comment: 27 pages, 13 figures; v2 minor corrections, typos corrected, Figure
13 replaced, references adde
Regular and irregular modulation of frequencies in limit cycle oscillator networks
Frequency modulation by perturbation is the essential trait that
differentiates limit cycle oscillators from phase oscillators. We studied
networks of identical limit cycle oscillators whose frequencies are modulated
sensitively by the change of their amplitudes, and demonstrated that the
frequencies sustainably take distributed values. We observed two complex
phenomena in the networks: stationarily distributed frequencies at a regular
interval, and continuous irregular modulation of frequencies. In the analysis
we reveal the mechanisms by which the frequencies are distributed, and show how
the sensitive modulation of frequencies produces these complex phenomena. We
also illustrate the topology of networks regulating the behaviors of the
systems.Comment: 4 pages, 2 figure
Black Hole Entropy in the presence of Chern-Simons Terms
We derive a formula for the black hole entropy in theories with gravitational
Chern-Simons terms, by generalizing Wald's argument which uses the Noether
charge. It correctly reproduces the entropy of three-dimensional black holes in
the presence of Chern-Simons term, which was previously obtained via indirect
methods.Comment: v2: 12 pages, added reference
Reactivity of neodymium carriers in deep sea sediments: Implications for boundary exchange and paleoceanography
The dissolved neodymium (Nd) isotopic distribution in the deep oceans is determined by continental weathering inputs, water mass advection, and boundary exchange between particulate and dissolved fractions. Reconstructions of past Nd isotopic variability may therefore provide evidence on temporal changes in continental weathering inputs and/or ocean circulation patterns over a range of timescales. However, such an approach is limited by uncertainty in the mechanisms and importance of the boundary exchange process, and the challenge in reliably recovering past seawater Nd isotopic composition (ĪµNd) from deep sea sediments. This study addresses these questions by investigating the processes involved in particulateāsolution interactions and their impact on Nd isotopes. A better understanding of boundary exchange also has wider implications for the oceanic cycling and budgets of other particle-reactive elements. Sequential acid-reductive leaching experiments at pH ā¼2ā5 on deep sea sediments from the western Indian Ocean enable us to investigate natural boundary exchange processes over a timescale appropriate to laboratory experiments. We provide evidence that both the dissolution of solid phases and exchange processes influence the ĪµNd of leachates, which suggests that both processes may contribute to boundary exchange. We use major element and rare earth element (REE) data to investigate the pools of Nd that are accessed and demonstrate that sediment leachate ĪµNd values cannot always be explained by admixture between an authigenic component and the bulk detrital component. For example, in core WIND 24B, acid-reductive leaching generates ĪµNd values between ā11 and ā6 as a function of solution/solid ratios and leaching times, whereas the authigenic components have ĪµNd ā ā11 and the bulk detrital component has ĪµNd ā ā15. We infer that leaching in the Mascarene Basin accesses authigenic components and a minor radiogenic volcanic component that is more reactive than Madagascan-derived clays. The preferential mobilisation of such a minor component demonstrates that the Nd released by boundary exchange could often have a significantly different ĪµNd composition than the bulk detrital sediment. These experiments further demonstrate certain limitations on the use of acid-reductive leaching to extract the ĪµNd composition of the authigenic fraction of bulk deep sea sediments. For example, the detrital component may contain a reactive fraction which is also acid-extractible, while the incongruent nature of this dissolution suggests that it is often inappropriate to use the bulk detrital sediment elemental chemistry and/or ĪµNd composition when assessing possible detrital contamination of leachates. Based on the highly systematic controls observed, and evidence from REE patterns on the phases extracted, we suggest two approaches that lead to the most reliable extraction of the authigenic ĪµNd component and good agreement with foraminiferal-based approaches; either (i) leaching of sediments without a prior decarbonation step, or (ii) the use of short leaching times and low solution/solid ratios throughout
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