The contemporary view of the fundamental role of time in physics generally ignores its most obvious characteric, namely its flow. Studies in the foundations of relativistic mechanics during the past decade have shown that the dynamical evolution of a system can be treated in a manifestly covariant way, in terms of the solution of a system of canonical Hamilton type equations, by considering the space-time coordinates and momenta ofevents as its fundamental description. The evolution of the events, as functions of (...) a universal invariant world, or historical, time, traces out the world lines that represent the phenomena (e.g., particles) which are observed in the laboratory. The positions in time of each of the events, i.e., the time of their potential detection, are, in this framework, controlled by this universal parameter τ, the time at which they are generated (and may proceed in the positive or negative sense). We find that the notion of thestate of a system requires generalization; at any given τ, it involves information about the system at timest(τ) ≠ τ. The correlation of what may be measured att(τ) with what is generated at τ is necessarily quite rigid, and is related covariantly to the spacelike correlations found in interference experiments. We find, furthermore, that interaction with Maxwell electromagnetism leads back to a static picture of the world, with no real evolution. As a consequence of this result, and the requirement of gauge invariance for the quantum mechanical evolution equation, we conclude that electromagnetism is described by a pre-Maxwell field, whose τ-integral (or asymptotic behavior as τ → ∞) may be identified with the Maxwell field. We therefore consider the world of events in space time, interacting through τ-dependent pre-Maxwell fields, as far as electrodynamics is concerned, as the objective dynamical reality. Our perception of the world, through laboratory detectors and our eyes, are based onintegration over τ over intervals sufficiently large to obtain an aposteriori description of the phenomena which coincides with the Maxwell theory. Fundamental notions, such as the conservation of charge, rest on this construction. The decomposition of the common notion of time into two essentially different aspects, one associated with an unvarying flow, and the second with direct observation subject to dynamical modification, has profound philosophical consequences, of which we are able to explore here only a few. (shrink)

We consider a theory in which spacetime is a 4-dimensional manifold V4 embedded in an N-dimensional space VN. The dynamics is given by a first-order action which is a straightforward generalization of the well-known Nambu-Gotto string action. Instead of the latter action we then consider an equivalent action, a generalization of the Howe-Tucker action, which is a functional of the (extrinsic) embedding variables ηa(x) and of the (intrinsic) induced metric gυv (x) on V4. In the quantized theory we can define (...) an effective action by means of the Feynman path integral in which we functionally integrate over the embedding variables. What remains is functionally dependent solely on the induced metric. It is well known that the effective action so obtained contains the Ricci scalar R and its higher orders. But due to our special choice of a quantity, the so-called “matter” density ω(η) in VN entering the original first-order action, it turns out that the effective action contains also the source term. The latter is in general that of a p-dimensional membrane (p-brane). In particular we consider the case of bosonic point particles. Finally we discuss and clarify certain interpretational aspects of quantum mechanics from the viewpoint of our embedding model. (shrink)

The invariant evolution parameter τ is often used in the formulation of a so-called unconstrained relativistic quantum theoryof a point particle. Such a theory is very elegant, and contains the usual Klein-Gordon or the Dirac particle as a special case. In the present paper we extend the unconstrained theory to describe a continuous set of point particles forming a string or, in general, a membrane of arbitrary dimension p.The action of this system is not invariant with respect to reparametrizations of (...) the evolution parameter τ and therefore there is no constraints among the dynamical variables, and no need for ghosts in the quantized theory. Then we show that such an unconstrained membrane is equivalent to a wiggly membranewhich has variable tension on its (p+1)-dimensional worldsheet. The equations of motion admit the usual well-known Dirac-Nambu-Goto membranes as particular solutions. (shrink)

The purpose of this paper is to review relativistic quantum theories with an invariant evolution parameter. Parametrized relativistic quantum theories (PRQT) have appeared under such names as constraint Hamiltonian dynamics, four-space formalism, indefinite mass, micrononcausal quantum theory, parametrized path integral formalism, relativistic dynamics, Schwinger proper time method, stochastic interpretation of quantum mechanics and stochastic quantization. The review focuses on the fundamental concepts underlying the theories. Similarities as well as differences are highlighted, and an extensive bibliography is provided.