Higgsing the stringy higher spin symmetry

It has recently been argued that the symmetric orbifold theory of T4 is dual to string theory on AdS3 x S3 x T4 at the tensionless point. At this point in moduli space, the theory possesses a very large symmetry algebra that includes, in particular, a $W_\infty$ algebra capturing the gauge fields of a dual higher spin theory. Using conformal perturbation theory, we study the behaviour of the symmetry generators of the symmetric orbifold theory under the deformation that corresponds to switching on the string tension. We show that the generators fall nicely into Regge trajectories, with the higher spin fields corresponding to the leading Regge trajectory. We also estimate the form of the Regge trajectories for large spin, and find evidence for the familiar logarithmic behaviour, thereby suggesting that the symmetric orbifold theory is dual to an AdS background with pure RR flux.Comment: 27 pages, 1 figure, note added in version

The Effect of varying Ground-state Aromaticity on the First Molecular Electronic Hyperpolarizabilites of Organic Donor-Acceptor Molecules

A series of compounds of the form 4-dimethylaminophenyl–polyene–acceptor, where the polyene ranges from nothing to all-trans-1,3,5-hexatriene and the acceptor is 2-nitrovinyl, formyl, or 2,2-dicyanovinyl has been prepared and their β values measured by solution electric-field-induced second-harmonic generation; these molecules, which lose only one aromatic resonance upon charge-transfer excitation, show enhanced β compared to bi-aromatic molecules with the same substitution and total conjugation length, such as 4-dimethylamino-4′-nitrostilbene (DANS), a well-known benchmark for high β organic molecules

The First Molecular Electronic Hyperpolarizabilities of Highly Polarizable Organic Molecules: 2,6-Di-tert-butylindoanilines

The first molecular hyperpolarizabilities (β) of a series of 2,6-di-tert-butylindoanilines, measured by electric-field-induced second harmonic generation are somewhat more sensitive to donor strength than was found for analogously substituted nitrostilbenes, and dimethylindoaniline has a β roughly twice that of its 2,6 di-tert-butylated analogue, measured in chloroform; solvatochromic measurements on the former compound suggest that this decrease in hyperpolarizability is consistent with a bound-solvent effect

Local Density of States and Angle-Resolved Photoemission Spectral Function of an Inhomogeneous D-wave Superconductor

Nanoscale inhomogeneity seems to be a central feature of the d-wave superconductivity in the cuprates. Such a feature can strongly affect the local density of states (LDOS) and the spectral weight functions. Within the Bogoliubov-de Gennes formalism we examine various inhomogeneous configurations of the superconducting order parameter to see which ones better agree with the experimental data. Nanoscale large amplitude oscillations in the order parameter seem to fit the LDOS data for the underdoped cuprates. The one-particle spectral function for a general inhomogeneous configuration exhibits a coherent peak in the nodal direction. In contrast, the spectral function in the antinodal region is easily rendered incoherent by the inhomogeneity. This throws new light on the dichotomy between the nodal and antinodal quasiparticles in the underdoped cuprates.Comment: 5 pages, 9 pictures. Phys. Rev. B (in press

Soft computing for intelligent data analysis

Intelligent data analysis (IDA) is an interdisciplinary study concerned with the effective analysis of data. The paper briefly looks at some of the key issues in intelligent data analysis, discusses the opportunities for soft computing in this context, and presents several IDA case studies in which soft computing has played key roles. These studies are all concerned with complex real-world problem solving, including consistency checking between mass spectral data with proposed chemical structures, screening for glaucoma and other eye diseases, forecasting of visual field deterioration, and diagnosis in an oil refinery involving multivariate time series. Bayesian networks, evolutionary computation, neural networks, and machine learning in general are some of those soft computing techniques effectively used in these studies

Synthesis and First Hyperpolarizabilities of Acceptor-substituted β-apo-8’-Carotenal Derived Compounds

The synthesis and second-order nonlinear optical properties of acceptor-substituted biologically derived β-apo-8′-carotenal compounds are reported; electric field-induced second harmonic generation (EFISH) measurements give values of β(0) which are 2–6 times greater than for 4-N,N-dimethylamino-4′-nitrostilbene (DANS)

Stress Tensors of Multiparticle Collision Dynamics Fluids

Stress tensors are derived for the multiparticle collision dynamics algorithm, a particle-based mesoscale simulation method for fluctuating fluids, resembling those of atomistic or molecular systems. Systems with periodic boundary conditions as well as fluids confined in a slit are considered. For every case, two equivalent expressions for the tensor are provided, the internal stress tensor, which involves all degrees of freedom of a system, and the external stress, which only includes the interactions with the confining surfaces. In addition, stress tensors for a system with embedded particles are determined. Based on the derived stress tensors, analytical expressions are calculated for the shear viscosity. Simulations illustrate the difference in fluctuations between the various derived expressions and yield very good agreement between the numerical results and the analytically derived expression for the viscosity

Chirally symmetric but confining dense and cold matter

The folklore tradition about the QCD phase diagram is that at the chiral restoration phase transition at finite density hadrons are deconfined and there appears the quark matter. We address this question within the only known exactly solvable confining and chirally symmetric model. It is postulated within this model that there exists linear Coulomb-like confining interaction. The chiral symmetry breaking and the quark Green function are obtained from the Schwinger-Dyson (gap) equation while the color-singlet meson spectrum results from the Bethe-Salpeter equation. We solve this model at T=0 and finite chemical potential $\mu$ and obtain a clear chiral restoration phase transition at the critical value \mu_{cr}. Below this value the spectrum is similar to the previously obtained one at \mu = 0. At \mu > \mu_{cr} the quarks are still confined and the physical spectrum consists of bound states which are arranged into a complete set of exact chiral multiplets. This explicitly demonstrates that a chirally symmetric matter consisting of confined but chirally symmetric hadrons at finite chemical potential is also possible in QCD. If so, there must be nontrivial implications for astrophysics.Comment: 7 pp; the paper has been expanded to make some technical details more clear; 3 new figures have been added. To appear in PR

Viscoplasticity and large-scale chain relaxation in glassy-polymeric strain hardening

A simple theory for glassy polymeric mechanical response which accounts for large scale chain relaxation is presented. It captures the crossover from perfect-plastic response to strong strain hardening as the degree of polymerization $N$ increases, without invoking entanglements. By relating hardening to interactions on the scale of monomers and chain segments, we correctly predict its magnitude. Strain activated relaxation arising from the need to maintain constant chain contour length reduces the $N$ dependence of the characteristic relaxation time by a factor $\sim \dot\epsilon N$ during active deformation at strain rate $\dot\epsilon$. This prediction is consistent with results from recent experiments and simulations, and we suggest how it may be further tested experimentally.Comment: The theoretical treatment of the mechanical response has been significantly revised, and the arguments for coherent relaxation during active deformation made more transparen