Modern Physics Letters A

The Heisenberg indeterminacy principle Δp_aΔq^a ~ ħ, relating canonically conjugate variables p_a and q^a, is quantified for the classical action obtained by the reduction of the ten-dimensional heterotic superstring theory to four dimensions, in the mini-superspace (Friedmann space-time) . There are two coordinates, α and , representing position and velocity, respectively, the canonical momenta being and . In both cases, the result can be expressed as an indeterminacy in the time, (Δt/t)². The fluctuations connecting position and velocity decrease with time and are always undetectably small, Δt/t ≲ 10⁻⁴⁴. But the fluctuations involving velocity and acceleration increase with time, and are evaluated at the time t_e of equipartition of radiation and matter in the universe. Translated first into a metric fluctuation , this is equivalent to a Gaussian, scale-invariant spectrum of density fluctuations of magnitude , where the dimensionless constant B depends only on the compactification scheme. For a Calabi–Yau internal space, the estimate B ≈ 3 implies that ζ ≈ 2 × 10⁻⁴, which is sufficient for the creation of galaxies and in approximate agreement with observations of the anisotropy of the cosmic microwave background radiation by COBE and at Tenerife.

A description is given on how to construct (0, 2) supersymmetric conformal field theories as coset models. These models may be used as non-trivial backgrounds for heterotic string theory. They are realized as a combination of an anomalously gauged Wess–Zumino–Witten model, right-moving supersymmetric fermions, and left-moving current algebra fermions. Requiring the sum of the gauge anomalies from the bosonic and fermionic sectors to cancel yields the final model. Applications discussed include exact models of extremal four-dimensional charged black holes and Taub–NUT solutions of string theory. These coset models may also be used to construct important families of (0, 2) supersymmetric heterotic string compactifications. The Kazama–Suzuki models are the left-right symmetric special case of these models.

In this paper, we construct irreducible q-tensor operators of rank 1/2 of quantum algebra SU_q(2) using generators of quantum superalgebra SU_q(2|1) and their general relations. By means of the property of q-tensor operators, we can easily obtain the irreducible representations. The method does not depend on any concrete realization of SU_q(2|1). The result holds in general.

An SO(N)-invariant algebra of extended superconformal symmetry is obtained in two dimensions with an arbitrary central charge, which besides the energy-momentum tensor contains the currents of 1/2, 1 and 3/2 dimensions.

Following the ideas of Ref. 3, to account for instability of 2-D black hole solution, we discuss possible imaginary string-loop corrections to the coefficient at the Einstein term in string effective action (EA). In closed bosonic string theory, such corrections appear because of the tachyon contribution to the integration measure over the moduli. In superstring theory, several possible sources of complex one-string-loop contributions to the EA are considered. It is argued that none of them can account for complex corrections to the Einstein term in the effective action.

In a space of d(d > 5) ordinary and d Grassmann coordinates, fields manifest in an ordinary four-dimensional subspace as spinor (1/2, 3/2), scalar, vector or tensor fields with the corresponding charges, according to two kinds of generators of the Lorentz transformations in the Grassmann space. Vielbeins and spin connections define gauge fields-gravitational and Yang–Mills. For d = 15 the theory offers the unification of all known charges — spins and Yang–Mills charges — of fermionic and bosonic fields and all known interactions.

A new class of potentials is generated for which exact solutions for one or few states are possible provided one of the potential parameters is assigned a fixed value and there is a constraint relation amongst the others. The method of construction of such conditionally quasi-exactly solvable potentials is illustrated by a few examples.

The value of α_s (M_z) emerging from the so-called global fits based mainly on the data at the Z peak (and assuming the standard model) is three standard deviations higher than the one stemming from the low-energy phenomenology. The corresponding value of Λ_QCD is very large, ~500 MeV, and is incompatible with crucial features of QCD. If persists, the discrepancy should be interpreted as due to contributions to the Z-quark-antiquark vertices which go beyond the standard model.

The puzzle of the absence of VP modes ψ → ρπ, , is now extended to the VT mode ψ′ → ω₀f₂(1270) from the recent BES run. This poses additional challenge to phenomenological theory. We study the new situation in terms of the hadron helicity conservation (HHC) theorem and the postulated existence of a trigluonia Omicron .

The quantum theory of fields with moving boundary conditions in four-dimensional space-time is studied. We consider the particular case of a scalar massless field between two infinite parallel plates moving with constant relative velocity. It is shown that this motion produces squeezed states, and creates 'particles' at the expense of the Casimir energy.