Nonequilibrium statistical mechanics in the general theory of relativity I. A general formalism

This is the first in a series of papers, the overall objective of which is the formulation of a new covariant approach to nonequilibrium statistical mechanics in classical general relativity. The object here is the development of a tractable theory for self-gravitating systems. It is argued that the “state” of an N-particle system may be characterized by an N-particle distribution function, defined in an 8N-dimensional phase space, which satisfies a collection of N conservation equations. by mapping the true physics onto a fictitious “background” spacetime, which may be chosen to satisfy some “average” field equations, one then obtains a useful covariant notion of “evolution” in response to a fluctuating “gravitational force.” For many cases of practical interest, one may suppose (i) that these fluctuating forces satisfy linear field equations and (ii) that they may be modeled by a direct interaction. In this case, one can use a relativistic projection operator formalism to derive exact closed equations for the evolution of such objects as an appropriately defined reduced one-particle distribution function. By capturing, in a natural way, the notion of a dilute gas, or impulse, approximation, one is then led to a comparatively simple equation for the one-particle distribution. If, furthermore, one treats the effects of the fluctuating forces as “localized” in space and time, one obtains a tractable kinetic equation which reduces, in the newtonian limit, to the standard Landau equation.     

An alternative to quantum theory

In a recent paper we have shown that continuous sets of resonances (as expressed by the nonvanishing of the kinetic collision operator) result in divergences in the traditional unitary transformation theory in addition to the usual ultraviolet divergences. Therefore, relaxation processes and lifetimes cannot be eliminated by unitary transformations diagonalizing the Hamiltonian. For this reason, we introduce a more general transformation theory based on nonfactorizable superoperators which “block diagonalize” the Hamiltonian superoperator and eliminate the divergence of the unitary transformation. This leads to a new concept of “observables” which are represented in general by operators which are both noncommuting and nondistributive. For example, to a single energy level we now associate a set of numbers corresponding to a probability distribution whose width is determined by the lifetime of the state. This new approach incorporates dissipation into the frame of quantum mechanics. It leads directly to a number of predictions such as the existence of a new anomalous Lamb shift dependent on lifetime as well as the appearance of a broken “time symmetry” in the structure of the energy spectrum. As this symmetry breaking depends on the arrow of time (thermodynamic equilibrium is approached in our future and not in our past) which is a property of our universe as a whole, we may call this new effect the “cosmological” Lamb shift. Of course subsequent experiments will have to explore the existence of this effect. Other consequences of this approach are briefly mentioned and will be developed in subsequent papers.     

Interpretation of the d-parameters,occurring in the Mayants-Averbukh theory of infrared intensity,in terms of the bond dipole moment concept: Equivalence with the valence-optical theory in the zeroth approximation for linear and planar molecules

From a comparison with the valence-optical theory of infrared intensity in the zeroth approximation, it is suggested that the d-parameters (elements of the effective charge tensor D_n⁰ of a bond) occurring in the Mayants-Averbukh theory can be expressed in terms of bond dipole moment components and their derivatives with respect to components of the Cartesian bond displacement vector. With this interpretation, which may be suitable for practical application, the Mayants-Averbukh theory formally appears as a combination of the “special” and the generalized valence-optical theory. In particular, it is found that for linear molecules the Mayants-Averbukh theory is equivalent to the “special” valence-optical theory in the zeroth approximation. For planar molecules the Mayants-Averbukh theory is equivalent to the generalized valence-optical theory (zeroth approximation) for in-plane modes and to the “special” valence-optical theory for out-of-plane modes.     

Mesons in the large-N collective field method

The large-N limit of SU(N) matrix quantum mechanics has been studied recently as a model for large-N Yang-Mills theory. Here we solve this model with fundamental representation fermions (“quarks”) added. The “meson” spectrum is given by an integral equation and exhibits asymptotically linear “Regge trajectories” with the same spacing as that of the “glueballs”.     

Topological bootstrap theory of hadrons

A topological framework is constructed for anS-matrix bootstrap theory of particles. Each component of anS-matrix topological expansion is associated with a pair of intersecting “quantum” and “classical” surfaces whose complexity exhibits an entropy property. The bounded classical surface embeds graphs that carry the direct observables — energymomentum, spin and electric charge. The closed quantum surface carries a triangulation whose orientations represent internal quantum numbers — which turn out to be baryon number, lepton number and flavor. A form of “color” automatically appears. All strong-interaction components of the expansion are generated through “Landau connected sums” from “zeroentropy” surface pairs — which are self generating. Elementary particles correspond to triangulated areas on the quantum surface; consistency at zero entropy determines allowed hadrondisks on quantum spheres together with the associated quantum numbers. Elementary topological hadrons turn out to include mesons, baryons and baryoniums, with quarks appearing as “peripheral triangles” (along the perimenters of hadron disks) whose attachments correspond to a total of 8 flavors as well as spin. Individual quarks do not carry momentum and cannot be hadrons; quark confinement is automatic. Also appearing within hadron disks are “core triangles” that carry baryon number and electric charge but no flavor or spin. Hadron disks have quantum numbers that accord with the lowestmass physically-observed mesons and baryons. The relation of topological theory to QCD is discussed.     

Quantum tetrahedra and simplicial spin networks

A new link between tetrahedra and the group SU(2) is pointed out: by associating to each face of a tetrahedron an irreducible unitary SU(2) representation and by imposing that the faces close, the concept of the quantum tetrahedron is seen to emerge. The Hilbert space of the quantum tetrahedron is introduced and it is shown that, due to an uncertainty relation, the “geometry of the tetrahedron” exists only in the sense of “mean geometry”.A kinematical model of quantum gauge theory is also proposed, which shares the advantages of the loop representation approach in handling in a simple way gauge- and diff-invariances at a quantum level, but is completely combinatorial. The concept of quantum tetrahedron finds a natural application in this model, giving a possible interpretation of SU(2) spin networks in terms of geometrical objects.     

Field theoretic bags: Some formal considerations

We consider some formal aspects of localized quasi-classical solutions (“bags”) in a field theory involving a “quark” field Ψ and a scalar (“confining”) field Φ, where the latter has a quartic self-coupling and is coupled strongly to the quark field via a Yukawa couplingfΨΨΦ. Renormalization-already coming in at the quasi-classical level through the quark “sea” contribution-and translation invariance are discussed in some detail.     

On the physics of λφ4 in aℝ2×S 1 space

The physics of λφ⁴ quantum field theory in a space with a closed dimension (?²×S ¹) is studied on the basis of a varitional approach, which supports the existence of two interacting phases of the minkowskian λφ⁴ on nonperturbative grounds. As the lengthL of the closed dimension decreases (1/L becomes the relevant scale), triviality restoration is encountered in the “precarious” phase, as well as symmetry restoration in the “autonomous” phase. The close relation to the finite temperature formalism allows to uncover a temperature symmetry restoration of theT=0 spontaneously broken phase.     

A probabilistic analysis of the difficulties of unifying quantum mechanics with the theory of relativity

A procedure is given for the transformation of quantum mechanical operator equations into stochastic equations. The stochastic equations reveal a simple correlation between quantum mechanics and classical mechanics: Quantum mechanics operates with “optimal estimations,” classical mechanics is the limit of “complete information.” In this connection, Schrödinger's substitution relationsp _x → -i? ?/?x, etc, reveal themselves as exact mathematical transformation formulas. The stochastic version of quantum mechanical equations provides an explanation for the difficulties in correlating quantum mechanics and the theory of relativity: In physics “time” is always thought of as a numerical parameter; but in the present formalism of physics “time” is described by two formally totally different quantities. One of these two “times” is a numerical parameter and the other a random variable. This last concept of time shows all the properties required by the theory of relativity and is therefore to be considered as the relativistic time.     

Orientational dynamics of superfluid 3He: A “two-fluid” model. II. Orbital dynamics

We present a phenomenological theory of the homogeneous orbital dynamics of the class of “separable” anisotropic superfluid phases which includes the ABM state generally identified with ³He-A. The theory is developed by analogy with the spin dynamics described in the first paper of this series; the basic variables are the orientation of the Cooper-pair wavefunction (in the ABM phase, the l-vector) and a quantity K which we visualize as the “pseudo-angular momentum” of the Cooper pairs but which must be distinguished, in general, from the total orbital angular momentum of the system. In the ABM case l is the analog of d in the spin dynamics and K of the “superfluid spin” S_p. Important points of difference from the spin case which are taken into account include the fact that a rotation of l without a simultaneous rotation of the normal-component distribution strongly increases the energy of the system (“normal locking”), and that the equilibrium value of K is zero even for finite total angular momentum. The theory does not claim to handle correctly effects associated with any intrinsic angular momentum arising from particle-hole asymmetry, but it is shown that the magnitude of this quantity can be estimated directly from experimental data and is extremely small; also, the Landau damping does not emerge automatically from the theory, but can be put in in an ad hoc way. With these provisos the theory should be valid for all frequencies $\text{ω ?}\text{Δ(T)}\text{h}\text{?}$ irrespective of the value of ωτ. (Δ = gap parameter, τ = quasi-particle relaxation time.) It disagrees with all existing phenomenological theories of comparable generality, although the disagreement with that of Volovik and Mineev is confined to the “gapless” region very close to T_c.The phenomenological equations of motion, which are similar in general form to those of the spin dynamics with damping, involve an “orbital susceptibility of the Cooper pairs” χ_orb(T). We give a possible microscopic definition of the variable K and use it to calculate χ_orb(T) for a general phase of the “separable” type. The theory is checked by inserting the resulting formula in the phenomenological equations for ωτ ? 1 and comparing with the results of a fully microscopic calculation based on the collisionless kinetic equation; precise agreement is obtained for both the ABM and the (real) polar phase, showing that the complex nature of the ABM phase and the associated “pair angular momentum” is largely irrelevant to its orbital dynamics. We note also that the phenomenological theory gives a good qualitative picture even when ω ～ Δ(T), e.g., for the flapping mode near T_c. Our theory permits a simple and unified calculation of (1) the Cross-Anderson viscous torque in the overdamped regime, (2) the flapping-mode frequency near zero temperature, (3) orbital effects on the NMR, both at low temperatures and near T_c, (4) the orbit wave spectrum at zero temperature (this requires a generalization to inhomogeneous situations which is possible at T = 0 but probably not elsewhere). We also discuss the possibility of experiments of the Einstein-de Haas type. Generally speaking, our results for any one particular application can be also obtained from some alternative theory, but in the case of orbital and spin relaxation very close to T_c (within the “gapless” region) our predictions, while somewhat tentative and qualitative, appear to disagree with those of all existing theories. We discuss briefly how our approach could be extended to apply to more general phases.     

A Dynamics for Discrete Quantum Gravity

This paper is based on the causal set approach to discrete quantum gravity. We first describe a classical sequential growth process (CSGP) in which the universe grows one element at a time in discrete steps. At each step the process has the form of a causal set (causet) and the “completed” universe is given by a path through a discretely growing chain of causets. We then quantize the CSGP by forming a Hilbert space H on the set of paths. The quantum dynamics is governed by a sequence of positive operators ρ _n on H that satisfy normalization and consistency conditions. The pair (H,{ρ _n }) is called a quantum sequential growth process (QSGP). We next discuss a concrete realization of a QSGP in terms of a natural quantum action. This gives an amplitude process related to the “sum over histories” approach to quantum mechanics. Finally, we briefly discuss a discrete form of Einstein’s field equation and speculate how this may be employed to compare the present framework with classical general relativity theory.     

Application of the Difference Gaussian Rules to Solution of Hyperbolic Problems: II. Global Expansion

This work is the sequel to S. Asvadurov et al. (2000, J. Comput. Phys.158, 116), where we considered a grid refinement approach for second-order finite-difference time domain schemes. This approach permits one to compute solutions of certain wave equations with exponential superconvergence. An algorithm was presented that generates a special sequence of grid steps, called “optimal”, such that a standard finite-difference discretization that uses this grid produces an accurate approximation to the Neumann-to-Dirichlet map. It was demonstrated that the application of this approach to some problems in, e.g., elastodynamics results in a computational cost that is an order of magnitude lower than that of the standard scheme with equally spaced gridnodes, which produces the same accuracy. The main drawback of the presented approach was that the accurate solution could be obtained only at some a priori selected points (receivers). Here we present an algorithm that, given a solution on the coarse “optimal” grid, accurately reconstructs the solution of the corresponding fine equidistant grid with steps that are approximately equal to the minimal step of the optimal (strongly nonuniform) grid. This “expansion” algorithm is based on postprocessing of the approximate solution, is local in time (but not in space), and has a cost comparable to that of the discrete Fourier transform. An approximate inverse to the “expansion” procedure—the “reduction” algorithm—is also presented. We show different applications of the developed procedures, including refinement of a nonmatching grid. Numerical examples for scalar wave propagation and 2.5D cylindrical elasticity are presented.     

Unitary representations of non-compact supergroups

We give a general theory for the construction of oscillator-like unitary irreducible representations (UIRs) of non-compact supergroups in a super Fock space. This construction applies to all non-compact supergroupsG whose coset spaceG/K with respect to their maximal compact subsupergroupK is “Hermitean supersymmetric”. We illustrate our method with the example of SU(m, p/n+q) by giving its oscillator-like UIRs in a “particle state” basis as well as “supercoherent state basis”. The same class of UIRs can also be realized over the “super Hilbert spaces” of holomorphic functions of aZ variable labelling the coherent states.     

Resonant charge exchange with the p-electron transition

The asymptotic resonant charge exchange theory is developed for slow collisions of atoms and ions with valent p-electrons. Because of a small rotation angle of the molecular axis in the course of the p-electron transition, the resonant charge exchange cross section is not sensitive to the rotational energy of colliding particles, and the cross sections are nearly equal for cases “a”, “b”, and “d” of the Hund coupling, and also for cases “c” and “e” of the Hund coupling. The cross sections of the resonant charge exchange process are evaluated under various conditions and for various elements of the periodical table with p-electron shells of atoms and ions.     

Nonlinear Schrödinger equations from prequantum classical statistical field theory

We derive some important features of the standard quantum mechanics from a certain classical-like model—prequantum classical statistical field theory, PCSFT. In this approach correspondence between classical and quantum quantities is established through asymptotic expansions. PCSFT induces not only linear Schrödinger's equation, but also its nonlinear generalizations. This coupling with “nonlinear wave mechanics” is used to evaluate the small parameter of PCSFT.     

Description of physical systems

A general “logical” scheme, containing both classical and quantum mechanics, is developed on the basis of plausible axioms. We introduce the division of states and yes-no measurements into sharp and diffuse ones, and prove that sharp states possess their carriers. Owing to this result, the existence of lattice joins and meets is proved for a wide class of elements of the logic. This “semi-lattice” structure gives the familiar lattice picture for special cases of classical and quantum mechanics. The notion of quantum superposition is introduced in this general scheme. It is proved that if in a theory appear nontrivial quantum superpositions, then this theory is “undeterministic” and vise versa. Further analysis of the pure state space leads to the construction of the canonical embedding of the general logic into an orthomodular complete ortho-lattice. After defining the probability of transition between pure states, the pure state space appears to be a generalization of Mielnik's “probability space” of quantum mechanics.