Large N Gauge Theories and Anti-de Sitter Bag Model

Using a proposal of Maldacena one describes the large N limit of gauge theories in terms of supergravity solutions on anti-de Sitter space. From this point of view we discuss a possible scenario for quark confinement in gauge theory by describing hadrons as strongly curved universes. In particular an interpretation of black hole as a bag model in SQCD is discussed. One relates the mystery of curvature singularities in classical general relativity with the mystery of quark confinement. The AdS bag model is defined by computing the probe membrane action in supergravity background. It naturally implies the "Cheshire Cat bag" principle. The confining pressure in the MIT bag model is related with the cosmological constant in the AdS bag model. The Skyrme model is interpreted as an effective theory describing black holes.Comment: 6 pages, Late

Planckian Energy Scattering of D-branes and M(atrix) Theory in Curved Space

We argue that black p-branes will occur in the collision of D0-branes at Planckian energies. This extents the Amati, Ciafaloni and Veneziano and 't Hooft conjecture that black holes occur in the collision of two light particles at Planckian energies. We discuss a possible scenario for such a process by using colliding plane gravitational waves. D-branes in the presence of black holes are discussed. M(atrix) theory and matrix string in curved space are considered. A violation of quantum coherence in M(atrix) theory is noticed.Comment: 5 pages, Late

Affine Strings

A new model of bosonic strings is considered. An action of the model is the sum of the standard string action and a term describing an interaction of a metric with a linear (affine) connection. The Lagrangian of this interaction is an arbitrary analytic function $f(R)$ of the scalar curvature. This is a classically integrable model. The space of classical solutions of the theory consists from sectors with constant curvature. In each sector the equations of motion reduce to the standard string equations and to an additional constant curvature equation for the linear connection. A bifurcation in the space of all Lagrangians takes place. Quantization of the model is briefly discussed. In a quasiclassical approximation one gets the standard string model with a fluctuating cosmological constant. The Lagrangian $f(R)$, like Morse function, governs transitions between manifolds with different topologies.Comment: 9 pages, SMI-2-9

On the Second Quantization of M(atrix) Theory

The second quantization of M(atrix) theory in the free (Boltzmannian) Fock space is considered. It provides a possible framework to the recent Susskind proposal that U(N) supersymmetic Yang-Mills theories for all N might be embedded in a single dynamical system. The second quantization of M(atrix) theory can also be useful for the study of the Lorentz symmetry and for the consideration of processes with creation and annihilation of D-branes.Comment: 3 pages, Latex, an explicit expression for the interaction Hamiltonian in the Boltzmannian Fock space is give

Models of Quantum Computers and Decoherence Problem

Mathematical models of quantum computers such as a multidimensional quantum Turing machine and quantum circuits are described and its relations with lattice spin models are discussed. One of the main open problems one has to solve if one wants to build a quantum computer is the decoherence due to the coupling with the environment. We propose a possible solution of this problem by using a control of parameters of the system. This proposal is based on the analysis of the spin-boson Hamiltonian performed in the stochastic limit approximation.Comment: 14 pages, Latex, Invited talk at the International Conference on Quantum Information, Meijo University, Nagoya, 4-8 Nov.1997, To be published in Proc. of the Conferenc

D-branes, Black Holes and SU(∞)SU(\infty) Gauge Theory

We discuss an application of the known in QCD large $N$ expansion to strings and supermembranes in the strong coupling. In particular we use the recently obtained master field describing $SU(\infty)$ gauge theory to argue that quantum extreme black holes obey quantum Boltzmann (infinite) statistics. This supports a topological argument by Strominger that black holes obey infinite statistics. We also speculate on a formulation of $X$-theory of strings and p-branes as theory of Grothendieck's motives. The partition function is expressed in terms of $L$-function of a motive. The Beilinson conjectures on the values of $L$-functions are interpreted as dealing with the cosmological constant problem.Comment: 4 pages, latex. Invited talk at the Second International Sakharov Conference on Physics, Moscow, May 199

Quantum white noise with singular non-linear interaction

A model of a system driven by quantum white noise with singular quadratic self--interaction is considered and an exact solution for the evolution operator is found. It is shown that the renormalized square of the squeezed classical white noise is equivalent to the quantum Poisson process. We describe how equations driven by nonlinear functionals of white noise can be derived in nonlinear quantum optics by using the stochastic approximation.Comment: 8 pages, Late

Metric Fluctuations in Brane Worlds

Recently a realization of the four-dimensional gravity on a brane in five-dimensional spacetime has been discussed. Randall and Sundrum have shown that the equation for the longitudinal components of the metric fluctuations admit a normalizable zero mode solution, which has been interpreted as the localized gravity on the brane. We point out that the equation for the transverse components of the metric fluctuations has a solutions which is not localized on the brane. This indicates that probably the effective theory is unstable or, in other words, actually it is not four-dimensional but five-dimensional. Perhaps a modification of the proposal by using matter fields can lead to the trapping of gravity to the brane.Comment: 6 pages, LaTeX, Missed term in eq.(15) is added, which does not change the resul

Quantum Multipole Noise and Generalized Quantum Stochastic Equations

A notion of quantum multipole (in particular, dipole) noise is considered. Quantum dipole noise is an analogue of quantum white noise but it acts in a Fock space with indefinite metric. Quantum {\it white} noise describes the leading term in the stochastic limit approximation to quantum dynamics while quantum {\it multipole} noise describes the corrections to the leading term. We obtain and study the generalized quantum stochastic equations describing corrections to the stochastic limit which include quantum dipole noise.Comment: Replaced with version published in IDAQP. Terminology is change

Cosmological Daemon

Classical versions of the Big Bang cosmological models of the universe contain a singularity at the start of time, hence the time variable in the field equations should run over a half-line. Nonlocal string field theory equations with infinite number of derivatives are considered and an important difference between nonlocal operators on the whole real line and on a half-line is pointed out. We use the heat equation method and show that on the half-line in addition to the usual initial data a new arbitrary function (external source) occurs that we call the daemon function. The daemon function governs the evolution of the universe similar to Maxwell`s demon in thermodynamics. The universe and multiverse are open systems interacting with the daemon environment. In the simplest case the nonlocal scalar field reduces to the usual local scalar field coupled with an external source which is discussed in the stochastic approach to inflation. The daemon source can help to get the chaotic inflation scenario with a small scalar field.Comment: LATEX, 31 pages, Sect. "Inflation and External Sources" and refs. are adde