17 research outputs found
On direct and crossed channel asymptotics of four-point functions in AdS/CFT correspondence
We analyse the leading logarithmic singularities in direct and crossed
channel limit of the four-point functions in dilaton-axion sector of type IIB
supergravity on in AdS/CFT correspondence. Logarithms do not cancel
in the full correlator in both channels.Comment: Revised version, typos corrected, 9 pages, no figure
A Family of Quasi-solvable Quantum Many-body Systems
We construct a family of quasi-solvable quantum many-body systems by an
algebraic method. The models contain up to two-body interactions and have
permutation symmetry. We classify these models under the consideration of
invariance property. It turns out that this family includes the rational,
hyperbolic (trigonometric) and elliptic Inozemtsev models as the particular
cases.Comment: 9 pages, REVTeX4, final versio
Free-Field Realization of D-dimensional Cylindrical Gravitational Waves
We find two-dimensional free-field variables for D-dimensional general
relativity on spacetimes with D-2 commuting spacelike Killing vector fields and
non-compact spatial sections for D>4. We show that there is a canonical
transformation which maps the corresponding two-dimensional dilaton gravity
theory into a two-dimensional diffeomorphism invariant theory of the free-field
variables. We also show that the spacetime metric components can be expressed
as asymptotic series in negative powers of the dilaton, with coefficients which
can be determined in terms of the free fields.Comment: 15 pages, Late
Calculation of 1-loop Hexagon Amplitudes in the Yukawa Model
We calculate a class of one-loop six-point amplitudes in the Yukawa model.
The construction of multi-particle amplitudes is done in the string inspired
formalism and compared to the Feynman diagrammatic approach. We show that there
exists a surprisingly efficient way of calculating such amplitudes by using
cyclic identities of kinematic coefficients and discuss in detail cancellation
mechanisms of spurious terms. A collection of formulas which are useful for the
calculation of massless hexagon amplitudes is given.Comment: 15 pages Late
Four Dimensional Conformal Supergravity From AdS Space
Exploring the role of conformal theories of gravity in string theory, we show
that the minimal (N=2) gauged supergravities in five dimensions induce the
multiplets and transformations of N=1 four dimensional conformal supergravity
on the spacetime boundary. N=1 Poincare supergravity can be induced by
explicitly breaking the conformal invariance via a radial cutoff in the 5d
space. The AdS/CFT correspondence relates the maximal gauged supergravity in
five dimensions to N=4 super Yang-Mills on the 4d spacetime boundary. In this
context we show that the conformal anomaly of the gauge theory induces
conformal gravity on the boundary of the space and that this theory, via the
renormalization group, encapsulates the gravitational dynamics of the skin of
asymptotically AdS spacetimes. Our results have several applications to the
AdS/CFT correspondence and the Randall-Sundrum scenario.Comment: 20 pages, LaTeX. v3. references and minor comments adde
Establishing long-term measurements of halocarbons at Taunus Observatory
In late 2013, a whole air flask collection programme was started at Taunus Observatory (TO) in central Germany. Being a rural site in close proximity to the Rhine–Main area, Taunus Observatory allows assessment of emissions from a densely populated region. Owing to its altitude of 825 m, the site also regularly experiences background conditions, especially when air masses approach from north-westerly directions. With a large footprint area mainly covering central Europe north of the Alps, halocarbon measurements at the site have the potential to improve the database for estimation of regional and total European halogenated greenhouse gas emissions. Flask samples are collected weekly for offline analysis using a GC/MS system simultaneously employing a quadrupole as well as a time-of-flight mass spectrometer. As background reference, additional samples are collected approximately once every 2 weeks at the Mace Head Atmospheric Research Station (MHD) when air masses approach from the site's clean air sector. Thus the time series at TO can be linked to the in situ AGAGE measurements and the NOAA flask sampling programme at MHD. An iterative baseline identification procedure separates polluted samples from baseline data. While there is good agreement of baseline mixing ratios between TO and MHD, with a larger variability of mixing ratios at the continental site, measurements at TO are regularly influenced by elevated halocarbon mixing ratios. Here, first time series are presented for CFC-11, CFC-12, HCFC-22, HFC-134a, HFC-227ea, HFC-245fa, and dichloromethane. While atmospheric mixing ratios of the chlorofluorocarbons (CFCs) decrease, they increase for the hydrochlorofluorocarbons (HCFCs) and the hydrofluorocarbons (HFCs). Small unexpected differences between CFC-11 and CFC-12 are found with regard to frequency and relative enhancement of high mixing ratio events and seasonality, although production and use of both compounds are strictly regulated by the Montreal Protocol, and therefore a similar decrease in atmospheric mixing ratios should occur. Dichloromethane, a solvent about which recently concerns have been raised regarding its growing influence on stratospheric ozone depletion, does not show a significant trend with regard to both baseline mixing ratios and the occurrence of pollution events at Taunus Observatory for the time period covered, indicating stable emissions in the regions that influence the site. An analysis of trajectories from the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model reveals differences in halocarbon mixing ranges depending on air mass origin