Limited superradiant damping of small samples

We show that for samples small compared to a wavelength the maximum possible superradiant damping is severely limited by the shortness of the radiation-field-induced relaxation time T_Δ as compared to the superradiant lifetime T_S.     

Semirings on cones

A topological semiring is a triplet (S, +, ?) where S is a Hausdorff topological space, “+” and “?” are jointly continuous associative binary operations on S and “?” distributes across “+” on both sides. Recent work by J. Selden [16], K. R. Pearson [13], and Paul H. Karvellas [7] has provided information about and, in some cases, complete characterizations of (S, +, ?) when (S, +) or (S, ?) are specified. Herein, we consider the case in which (S, ?) is the one-point compactification of a closed proper cone in Eⁿ with vector addition extended so that the point at infinity is a zero. Further, if (S, +) is assumed to be a semilattice, we give a complete characterization of (S, +, ?).     

Weights of links and plaquettes in a random lattice

In a random lattice, links and plaquettes have varying sizes and orientations. Therefore, they should enter the action function with different weights. A particularly attractive choice of these weights is presented; its consequences for $\text{spin}\text{-0,}\text{1}\text{2}\text{and}\text{1}$ fields on such a lattice are discussed.     

Frequency shifts in emission and absorption by resonant systems ot two-level atoms

The frequency shifts in emission and absorption arising from resonant many-body interactions in a system of two-level atoms are discussed from several points of view: (1) in the language of superradiance, Dicke states, quantum electrodynamics and perturbation theory; (2) in the classical-path treatment of gaseous emission, with emphasis on the impact approximation; (3) by means of diagrams related to the temperature-Green's function formalism; (4) in the semiclassical model using the macroscopic Bloch vector; (5) through ordinary classical electromagnetic theory in a linear medium.     

Random lattice field theory: General formulation

A new type of lattice field theory is formulated in which the sites are chosen randomly in space. An algorithm is given for linking nearby sites; these links form the edges of non-overlapping simplices which fill the entire volume. All physical quantities averaged over such a lattice can therefore be translationally and rotationally symmetric.     

Tokuyama-type formulas for characters of type B

We obtain explicit formulas for the product of a deformed Weyl denominator with the character of an irreducible representation of the spin group Spin_2r+1(C), which is an analogue of the formulas of Tokuyama for Schur polynomials and Hamel–King for characters of symplectic groups. To give these, we start with a symplectic group and obtain such characters using the Casselman–Shalika formula. We then analyze this using objects which are naturally attached to the metaplectic double cover of an odd orthogonal group, which also has dual group Spin_2r+1(C).     

Use of high-performance liquid chromatography to quantitative thymine-containing pyrimidine dimers in DNA

We have developed two high-performance liquid chromatographic systems for the measurement of pyrimidine dimers in hydrolysates of DNA. Normal-phase chromatography on an NH₂ column in methanol—ethyl acetate (3:97) at an elution rate of 2.0 ml/min allowed quantitaion of thymine-containing (thymine-thymine plus thymine-uracil) pyrimidine dimers at levels as low as 0.1% of the total radioactivity as thymine in DNA. This system was unaffected by the presence of up to 1 mg of contaminating protein (bovine serum albumin) or 40 μg of DNA in hydrolysates prepared for chromatography. Reversed-phase chromatography on a μBondapak C₁₈ column allowed measurement of thymine-thymine dimers at concentrations as low as 0.02% of the total radioactivity. With 0.1% tetrahydrofuran in wateras the solvent at a flow-rate of up to 0.6 ml/min, thymine—thymine, thymine—uracil, and uracil—uracil dimers were completely resolved. We were not able to quantitate the latter two dimeric forms, however, owing to the presence of other radioactive components of undefined origin that eluted concomitantly with the uracil-containing dimers.