7,490 research outputs found
Geometries with Killing Spinors and Supersymmetric AdS Solutions
The seven and nine dimensional geometries associated with certain classes of
supersymmetric and solutions of type IIB and D=11 supergravity,
respectively, have many similarities with Sasaki-Einstein geometry. We further
elucidate their properties and also generalise them to higher odd dimensions by
introducing a new class of complex geometries in dimensions, specified
by a Riemannian metric, a scalar field and a closed three-form, which admit a
particular kind of Killing spinor. In particular, for , we show that
when the geometry in dimensions is a cone we obtain a class of
geometries in dimensions, specified by a Riemannian metric, a scalar
field and a closed two-form, which includes the seven and nine-dimensional
geometries mentioned above when , respectively. We also consider various
ansatz for the geometries and construct infinite classes of explicit examples
for all .Comment: 28 page
Experimental fitting to the bipolaronic model of the normal-state resistance of Bi_2Sr_2CaCu_2O_8 single crystals
Normal-state resistance data from Bi_2Sr_2CaCu_2O_8 single crystals were
fitted to the (bi)polaronic conduction model, ,
with satisfactory agreement over a wide temperature range. The fluctuating
conduction region is found to be much narrower than that in the usual sense, as
is the case for a charged Bose-gas. We estimate the effective (bi)polaron mass
to be ~ 4m_e.Comment: 2 pages + 2 postscript figures. Submitted to M2S-HTSC-VI(Houston)
Conferenc
Marginal Deformations of Field Theories with AdS_4 Duals
We generate new AdS_4 solutions of D=11 supergravity starting from AdS_4 x
X_7 solutions where X_7 has U(1)^3 isometry. We consider examples where X_7 is
weak G_2, Sasaki-Einstein or tri-Sasakian, corresponding to d=3 SCFTs with
N=1,2 or 3 supersymmetry, respectively, and where the deformed solutions
preserve N=1,2 or 1 supersymmetry, respectively. For the special cases when X_7
is M(3,2), Q(1,1,1) or N(1,1)_I we identify the exactly marginal deformation in
the dual field theory. We also show that the volume of supersymmetric 5-cycles
of N(1,1)_I agrees with the conformal dimension predicted by the baryons of the
dual field theory.Comment: 28 pages, 2 figures; v2. typos correcte
Highly selective detection of Hg2+ and MeHgI by di-pyridin-2-yl-[4-(2-pyridin-4-yl-vinyl)-phenyl]-amine and its zinc coordination polymer
©2016 the Partner Organisations. Solvothermal reaction of Zn(NO3)2·6H2O with di-pyridin-2-yl-[4-(2-pyridin-4-yl-vinyl)-phenyl]-amine (ppvppa) and 1,4-naphthalenedicarboxylic acid (1,4-H2NDC) in H2O and MeCN at 150 °C yielded a two-dimensional (2D) coordination Zn(ii) polymer [Zn(ppvppa)(1,4-NDC)]n (1). Compound 1 was characterized by elemental analysis, IR spectroscopy, powder X-ray diffraction, single-crystal X-ray diffraction and thermogravimetric analysis. Compound 1 consists of dimeric [Zn2(ppvppa)2] units linked by 1,4-NDC bridges to generate a 2D honeycomb network. Either compound 1 or ppvppa alone can detect Hg2+ or MeHgI selectively and with good sensitivity. Upon addition of Hg2+ ions to a MeCN solution of ppvppa, marked changes in the UV-vis and fluorescence spectra are observed, associated with colour changes, which are easily identified by the naked eye. The pyridinyl rings of ppvppa are coordinated to the Hg2+ ion. This motif in the presence of NO3- ions forms a binuclear complex [Hg2(ppvppa)2(NO3)4] (2), which has been characterized as the solvate [Hg2(ppvppa)2(NO3)4]·H2O·4MeCN (2·H2O·4MeCN) by single-crystal X-ray diffraction studies. In aqueous solution, compound 1 emits pale orange light at ambient temperature and the addition of Hg2+ or MeHgI induces an change of fluorescence color from pale orange to blue. Compound 1 is a promising candidate as a sensitive naked-eye indicator for Hg2+ or MeHgI in water under a UV lamp. Introduction to the international collaboration Prof. Lang and Prof. Brammer met with each other in Nanjing, China when Prof. Brammer taught lectures at Nanjing Tech University last November. Prof. Lang's research involves metal sulfide cluster chemistry, design and development of new coordination complex-based catalysts, bioinorganic chemistry related to mimicking metal sites of enzymes and proteins, and so on. Prof. Brammer's research interest covers supramolecular chemistry and crystal engineering, in particular host-guest chemistry and catalysis in metal-organic frameworks, reactions in molecular solids and fundamentals of intermolecular interactions. Both professors recognised their many mutual research interests and decided to initiate an international collaborative project in the area of coordination polymers. Both will visit the partner's lab in China and UK in the near future and expand this project to a higher level
The Coupled Cluster Method in Hamiltonian Lattice Field Theory
The coupled cluster or exp S form of the eigenvalue problem for lattice
Hamiltonian QCD (without quarks) is investigated. A new construction
prescription is given for the calculation of the relevant coupled cluster
matrix elements with respect to an orthogonal and independent loop space basis.
The method avoids the explicit introduction of gauge group coupling
coefficients by mapping the eigenvalue problem onto a suitable set of character
functions, which allows a simplified procedure. Using appropriate group
theoretical methods, we show that it is possible to set up the eigenvalue
problem for eigenstates having arbitrary lattice momentum and lattice angular
momentum.Comment: LaTeX, no figur
New Einstein-Sasaki and Einstein Spaces from Kerr-de Sitter
In this paper, which is an elaboration of our results in hep-th/0504225, we
construct new Einstein-Sasaki spaces L^{p,q,r_1,...,r_{n-1}} in all odd
dimensions D=2n+1\ge 5. They arise by taking certain BPS limits of the
Euclideanised Kerr-de Sitter metrics. This yields local Einstein-Sasaki metrics
of cohomogeneity n, with toric U(1)^{n+1} principal orbits, and n real
non-trivial parameters. By studying the structure of the degenerate orbits we
show that for appropriate choices of the parameters, characterised by the (n+1)
coprime integers (p,q,r_1,...,r_{n-1}), the local metrics extend smoothly onto
complete and non-singular compact Einstein-Sasaki manifolds
L^{p,q,r_1,...,r_{n-1}}. We also construct new complete and non-singular
compact Einstein spaces \Lambda^{p,q,r_1,...,r_n} in D=2n+1 that are not
Sasakian, by choosing parameters appropriately in the Euclideanised Kerr-de
Sitter metrics when no BPS limit is taken.Comment: latex, 26 page
1/4-BPS M-theory bubbles with SO(3) x SO(4) symmetry
In this paper we generalize the work of Lin, Lunin and Maldacena on the
classification of 1/2-BPS M-theory solutions to a specific class of 1/4-BPS
configurations. We are interested in the solutions of 11 dimensional
supergravity with symmetry, and it is shown that such
solutions are constructed over a one-parameter familiy of 4 dimensional almost
Calabi-Yau spaces. Through analytic continuations we can obtain M-theory
solutions having or factors. It is shown
that our result is equivalent to the solutions which have been recently
reported as the near-horizon geometry of M2 or M5-branes wrapped on 2 or
4-cycles in Calabi-Yau threefolds. We also discuss the hierarchy of M-theory
bubbles with different number of supersymmetries.Comment: 22 pages, JHEP3.cls; v2. revised version. showed that our results
agree with previous works hep-th/0605146 and hep-th/061219
Sequestered Dark Matter
We show that hidden-sector dark matter is a generic feature of the type IIB
string theory landscape and that its lifetime may allow for a discovery through
the observation of very energetic gamma-rays produced in the decay. Throats or,
equivalently, conformally sequestered hidden sectors are common in flux
compactifications and the energy deposited in these sectors can be calculated
if the reheating temperature of the standard model sector is known. Assuming
that throats with various warp factors are available in the compact manifold,
we determine which throats maximize the late-time abundance of sequestered dark
matter. For such throats, this abundance agrees with cosmological data if the
standard model reheating temperature was 10^10 - 10^11 GeV. In two distinct
scenarios, the mass of dark matter particles, i.e. the IR scale of the throat,
is either around 10^5 GeV or around 10^10 GeV. The lifetime and the decay
channels of our dark matter candidates depend crucially on the fact that the
Klebanov-Strassler throat is supersymmetric. Furthermore, the details of
supersymmetry breaking both in the throat and in the visible sector play an
essential role. We identify a number of scenarios where this type of dark
matter can be discovered via gamma-ray observations.Comment: 36 pages, 3 figures; v2: references added, v3: introduction extended
and typos correcte
Coupling of thermal and mass diffusion in regular binary thermal lattice-gases
We have constructed a regular binary thermal lattice-gas in which the thermal
diffusion and mass diffusion are coupled and form two nonpropagating diffusive
modes. The power spectrum is shown to be similar in structure as for the one in
real fluids, in which the central peak becomes a combination of coupled entropy
and concentration contributions. Our theoretical findings for the power spectra
are confirmed by computer simulations performed on this model.Comment: 5 pages including 3 figures in RevTex
Superlattice Patterns in Surface Waves
We report novel superlattice wave patterns at the interface of a fluid layer
driven vertically. These patterns are described most naturally in terms of two
interacting hexagonal sublattices. Two frequency forcing at very large aspect
ratio is utilized in this work. A superlattice pattern ("superlattice-I")
consisting of two hexagonal lattices oriented at a relative angle of 22^o is
obtained with a 6:7 ratio of forcing frequencies. Several theoretical
approaches that may be useful in understanding this pattern have been proposed.
In another example, the waves are fully described by two superimposed hexagonal
lattices with a wavelength ratio of sqrt(3), oriented at a relative angle of
30^o. The time dependence of this "superlattice-II" wave pattern is unusual.
The instantaneous patterns reveal a time-periodic stripe modulation that breaks
the 6-fold symmetry at any instant, but the stripes are absent in the time
average. The instantaneous patterns are not simply amplitude modulations of the
primary standing wave. A transition from the superlattice-II state to a 12-fold
quasi-crystalline pattern is observed by changing the relative phase of the two
forcing frequencies. Phase diagrams of the observed patterns (including
superlattices, quasicrystalline patterns, ordinary hexagons, and squares) are
obtained as a function of the amplitudes and relative phases of the driving
accelerations.Comment: 15 pages, 14 figures (gif), to appear in Physica
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