Tensor analysis and curvature in quantum space-time

Introducing quantum space-time into physics by means of the transformation language of noncommuting coordinates gives a simple scheme of generalizing the tensor analysis. The general covariance principle for the quantum space-time case is discussed, within which one can obtain the covariant structure of basic tensor quantities and the motion equation for a particle in a gravitational field. Definitions of covariant derivatives and curvature are also generalized in the given case. It turns out that the covariant structure of the Riemann-Christoffel curvature tensor is not preserved in quantum space-time. However, if the curvature tensor _v (z) is redetermined up to the value of theL ² term, then its covariant structure is achieved, and it, in turn, allows us to reconstruct the Einstein equation in quantum space-time.     

Quantum Space-Time: A Review

The review presents systematically the results of studies which develop an idea of quantum properties of space-time in the microworld or near exotic objects (black holes, magnetic monopoles and others). On the basis of this idea motion equations of nonrelativistic and relativistic particles are studied. It is shown that introducing concept of quantum space-time at small distances (or near superdense matter) leads to an additional force giving rise to appearance of spiral-like behaviour of a particle along its classical trajectory. Given method is generalized to nonrelativistic quantum mechanics and to motion of a particle in gravitational force. In the latter case, there appears to be an antigravitational effect in the motion of a particle leading to different value of free-fall time (at least for gravitational force of exotic objects) for particles with different masses. Gravitational consequences of quantum space-time and tensor structures of physical quantities are inveatigated in detail. From experimental data on testing relativity and anisotropy of inertia estimation L ≦ 10⁻²² cm on the value of the fundamental length is obtained.     

Proton decay in the theory of gravitation and the hypothesis of fundamental length

Proton decay is investigated within the framework of the theory of gravitation and of the concept of neutron oscillation. It is shown that the mechanism of proton decay is very sensitive to the value of the fundamental length.     

Nonlocal stochastic quantization of scalar electrodynamics

Quantization of the electromagnetic interactions of scalar charged particles is considered within the stochastic Langevin and Schwinger-Dyson equations with nonlocal white noise. Fulfillment of the gauge-invariant condition in such a scheme is studied in detail. Matrix elements of the vacuum polarization and self-energy diagrams of the scalar electrodynamics are calculated explicitly, which reduce to usual nonlocal scalar electrodynamic results.     

Extended electron and nonlocal electromagnetic interaction: The perturbation theory

The nonlocal interaction between electrons and electromagnetic fields is considered. It is shown that different contraction forms of interacting fields are equivalent to different nonlocal theories where nonlocality is connected to either the photon field or the electron field, or to both these fields simultaneously. The nonlocal theory where the electron carries nonlocality is studied in detail. The gauge invariance of this model is achieved by using thed-operation applying the perturbation theory. Primitive Feynman diagrams of the nonlocal theory are investigated and a restriction on the “size”l of the electron is obtained. From low-energy experimental data from tests of local quantum electrodynamics it follows thatl≦10⁻¹⁵ cm.     

Nonlocal Yukawa interaction and fermion mass-scale nonlocality

A nonlocal Yukawa interaction between the Higgs boson and the fundamental fermions is introduced. A simple form of this interaction allows us to calculate a particular mass-scale nonlocality for all fundamental fermions. A prediction is given for the mass of the Higgs boson (m _H ≈ 200 GeV).     

Stochastic and quantum space-time metrics and the weak-field limit

In this review we present a simple method of introducing stochastic and quantum metrics into gravitational theory at short distances in terms of small fluctuations around a classical background space-time. We consider only residual effects due to the stochastic (or quantum) theory of gravity and use a perturbative stochastization (or quantization) method. By using the general covariance and correspondence principles, we reconstruct the theory of gravitational, mechanical, electromagnetic, and quantum mechanical processes and tensor algebra in the space-time with stochastic and quantum metrics. Some consequences of the theory are also considered, in particular, it indicates that the value of the fundamental lengthl lies in the interval 10^–23l10^–22 cm.     

Theoretical estimate of the Higgs boson mass

It is assumed that the Higgs particle distorts space-time in its own neighborhood and generates a self-referential nonlinear field. Its almost flat space-time metric form gives a nonlinear equation of motion admitting soliton-like solutions. This in turn gives rise to a new type of wave—space-time (mass-transmitting) interactions allowing particles to acquire mass. The curvature of the (pseudo-) Riemannian manifold of a Higgs space-time yields the mass formulam ₂ ^WZ =d ³ x detGR _H (x)=1/4m ₂ ^H orm _H =182 GeV.