Peculiarities of The Orientational State of Liquid-Crystal Completely Aromatic Thermotropic Copolymer

Polarization far-IR spectroscopy has been used to carry out a comparative study of the spectra of granules and fibers of completely aromatic thermotropic liquid-crystal copolymer Vectra A950. The analysis of terahertz polarization IR spectra Vectra A950 showed that in contrast to the mid-IR, dichroic ratio of the absorption bands in the spectra of fibers and granules, substantially different. It is shown that the difference between the value and the orientation order parameter in the samples is determined by and correlated with the intensity of the local dynamics of polymer chains, such as the librational mobility of phenylene and naphthalene rings of the copolymer mesogens. The results suggest the possibility carrying out an independent evaluation of the spectroscopic parameters reflecting the properties of intermolecular interactions in oriented the liquid-crystalline polymers for their low-frequency spectra

Nonlinear optical response of a 2D quantum dot supercrystal

We investigate theoretically the nonlinear optical response of a two-dimensional supercrystal comprized of semiconductor quantum dots. An isolated quantum dot is modeled as a three-level ladder-like system with ground, one-exciton, and biexciton states. It is shown that the optical response of supercrystal demonstrate a rich nonlinear dynamics, including bistability, self-oscillations, and dynamical chaos

Superradiance without inversion in a cavity:Effects of cavity losses and relaxation in the system of emitters

We investigate theoretically inversionless superradiance of an ensemble of three-level emitters (with Λ-scheme of operating transition), placed in a cyclic cavity. Effects of cavity losses and emitter’s relaxation on the dynamics of superradiance are studied

Cooperative Emission from an Ensemble of Three-Level Λ Radiators in a Cavity:An Insight from the Viewpoint of Dynamics of Nonlinear Systems

Cooperative radiation emitted by an ensemble of three-level optical systems with a doublet in the ground state (Λ scheme), which is placed into a cyclic cavity, is studied theoretically. In contrast to the twolevel model of emitters, this process with such a configuration of operating transitions may occur without population inversion in the whole, if the doublet is prepared at the initial instant in a superposition (coherent) state. In the ideal case of a Hamilton system, in which the cavity losses and relaxation in the radiator ensemble are disregarded, the conservation laws are derived, which allow a substantial reduction of the dimension of the phase space of the model (ℝ11 → ℝ5) and the application of methods of dynamics of nonlinear systems for analyzing the three-level superradiance under these conditions. The possibility of different (both quasiperiodic and chaotic) scenarios of the three-level superradiance is demonstrated on the basis of Poincaré’s mappings. Global bifurcation of the system upon a transition from the conventional superradiance regime to inversionless one is revealed. The effects of cavity losses, as well as homogeneous and inhomogeneous broadening in the system of radiators on the regularities found are also discussed

Low-temperature quenching of one-dimensional localised Frenkel excitons

We present a theoretical analysis of low-temperature quenching of one-dimensional Frenkel excitons that are localised by moderate on-site (diagonal) uncorrelated disorder. Exciton diffusion is considered as an incoherent hopping over localization segments and is probed by the exciton fluorescence quenching at point traps. The rate equation is used to calculate the temperature dependence of the exciton quenching. The activation temperature of the diffusion is found to be of the order of the width of the exciton absorption band. We demonstrate that the intra-segment scattering is extremely important for the exciton diffusion. We discuss also experimental data on the fast exciton-exciton annihilation in linear molecular aggregates at low temperatures.Comment: 7 pages, 3 figures, accepted to Chem. Phys. Let

Schrödinger operators with δ and δ′-potentials supported on hypersurfaces

Self-adjoint Schrödinger operators with δ and δ′-potentials supported on a smooth compact hypersurface are defined explicitly via boundary conditions. The spectral properties of these operators are investigated, regularity results on the functions in their domains are obtained, and analogues of the Birman–Schwinger principle and a variant of Krein’s formula are shown. Furthermore, Schatten–von Neumann type estimates for the differences of the powers of the resolvents of the Schrödinger operators with δ and δ′-potentials, and the Schrödinger operator without a singular interaction are proved. An immediate consequence of these estimates is the existence and completeness of the wave operators of the corresponding scattering systems, as well as the unitary equivalence of the absolutely continuous parts of the singularly perturbed and unperturbed Schrödinger operators. In the proofs of our main theorems we make use of abstract methods from extension theory of symmetric operators, some algebraic considerations and results on elliptic regularity

A Novel Long Range Spin Chain and Planar N=4 Super Yang-Mills

We probe the long-range spin chain approach to planar N=4 gauge theory at high loop order. A recently employed hyperbolic spin chain invented by Inozemtsev is suitable for the SU(2) subsector of the state space up to three loops, but ceases to exhibit the conjectured thermodynamic scaling properties at higher orders. We indicate how this may be bypassed while nevertheless preserving integrability, and suggest the corresponding all-loop asymptotic Bethe ansatz. We also propose the local part of the all-loop gauge transfer matrix, leading to conjectures for the asymptotically exact formulae for all local commuting charges. The ansatz is finally shown to be related to a standard inhomogeneous spin chain. A comparison of our ansatz to semi-classical string theory uncovers a detailed, non-perturbative agreement between the corresponding expressions for the infinite tower of local charge densities. However, the respective Bethe equations differ slightly, and we end by refining and elaborating a previously proposed possible explanation for this disagreement.Comment: 48 pages, 1 figure. v2, further results added: discussion of the relationship to an inhomogeneous spin chain, normalization in sec 3 unified, v3: minor mistakes corrected, published versio

Tachyonic preheating using 2PI-1/N dynamics and the classical approximation

We study the process of tachyonic preheating using approximative quantum equations of motion derived from the 2PI effective action. The O(N) scalar (Higgs) field is assumed to experience a fast quench which is represented by an instantaneous flip of the sign of the mass parameter. The equations of motion are solved numerically on the lattice, and the Hartree and 1/N-NLO approximations are compared to the classical approximation. Classical dynamics is expected to be valid, since the occupation numbers can rise to large values during tachyonic preheating. We find that the classical approximation performs excellently at short and intermediate times, even for couplings in the larger region currently allowed for the SM Higgs. This is reassuring, since all previous numerical studies of tachyonic preheating and baryogenesis during tachyonic preheating have used classical dynamics. We also compare different initializations for the classical simulations.Comment: 32 pages, 21 figures. Published version: Some details added, section added, references added, conclusions unchange

Finite-Size Corrections to Anomalous Dimensions in N=4 SYM Theory

The scaling dimensions of large operators in N=4 supersymmetric Yang-Mills theory are dual to energies of semiclassical strings in AdS(5)xS(5). At one loop, the dimensions of large operators can be computed with the help of Bethe ansatz and can be directly compared to the string energies. We study finite-size corrections for Bethe states which should describe quantum corrections to energies of extended semiclassical strings.Comment: 10 page

Semiclassical Strings on AdS_5 x S^5/Z_M and Operators in Orbifold Field Theories

We show agreements, at one-loop level of field theory, between energies of semiclassical string states on AdS_5 x S^5/Z_M and anomalous dimensions of operators in N=0,1,2 orbifold field theories originating from N=4 SYM. On field theory side, one-loop anomalous dimension matrices can be regarded as Hamiltonians of spin chains with twisted boundary conditions. These are solvable by Bethe ansatz. On string side, twisted sectors emerge and we obtain some string configurations in twisted sectors. In SU(2) subsectors, we compare anomalous dimensions with string energies and see agreements. We also see agreements between sigma models of both sides in SU(2) and SU(3) subsectors.Comment: LaTeX, 23 pages, 4 figures; v2 minor corrections, added references; v3 typos corrected, published versio