Bosonization of non-relativistic fermions on a circle: Tomonaga's problem revisited

We use the recently developed tools for an exact bosonization of a finite number $N$ of non-relativistic fermions to discuss the classic Tomonaga problem. In the case of noninteracting fermions, the bosonized hamiltonian naturally splits into an O$(N)$ piece and an O$(1)$ piece. We show that in the large-N and low-energy limit, the O$(N)$ piece in the hamiltonian describes a massless relativistic boson, while the O$(1)$ piece gives rise to cubic self-interactions of the boson. At finite $N$ and high energies, the low-energy effective description breaks down and the exact bosonized hamiltonian must be used. We also comment on the connection between the Tomonaga problem and pure Yang-Mills theory on a cylinder. In the dual context of baby universes and multiple black holes in string theory, we point out that the O$(N)$ piece in our bosonized hamiltonian provides a simple understanding of the origin of two different kinds of nonperturbative O$(e^{-N})$ corrections to the black hole partition function.Comment: latex, 28 pages, 5 epsf figure

A Time-Dependent Classical Solution of C=1 String Field Theory and Non-Perturbative Effects

We describe a real-time classical solution of $c=1$ string field theory written in terms of the phase space density, $u(p,q,t)$, of the equivalent fermion theory. The solution corresponds to tunnelling of a single fermion above the filled fermi sea and leads to amplitudes that go as \exp(- C/ \gst). We discuss how one can use this technique to describe non-perturbative effects in the Marinari-Parisi model. We also discuss implications of this type of solution for the two-dimensional black hole.Comment: 23

Stringy Quantum Effects in 2-Dimensional Black-Hole

We discuss the classical 2-dim. black-hole in the framework of the non-perturbative formulation (in terms of non-relativistic fermions) of c=1 string field theory. We identify an off-shell operator whose classical equation of motion is that of tachyon in the classical graviton-dilaton black-hole background. The black-hole `singularity' is identified with the fermi surface in the phase space of a single fermion, and as such is a consequence of the semi-classical approximation. An exact treatment reveals that stringy quantum effects wash away the classical singularity.Comment: 17p, TIFR/TH/92-63; (v3) tex error correcte

Non-relativistic Fermions, Coadjoint Orbits of \winf\ and String Field Theory at c=1c=1

We apply the method of coadjoint orbits of \winf-algebra to the problem of non-relativistic fermions in one dimension. This leads to a geometric formulation of the quantum theory in terms of the quantum phase space distribution of the fermi fluid. The action has an infinite series expansion in the string coupling, which to leading order reduces to the previously discussed geometric action for the classical fermi fluid based on the group $w_\infty$ of area-preserving diffeomorphisms. We briefly discuss the strong coupling limit of the string theory which, unlike the weak coupling regime, does not seem to admit of a two dimensional space-time picture. Our methods are equally applicable to interacting fermions in one dimension.Comment: 22 page

Wave Propagation in Stringy Black Hole

We further study the nonperturbative formulation of two-dimensional black holes. We find a nonlinear differential equation satisfied by the tachyon in the black hole background. We show that singularities in the tachyon field configurations are always associated with divergent semiclassical expansions and are absent in the exact theory. We also discuss how the Euclidian black hole emerges from an analytically continued fermion theory that corresponds to the right side up harmonic oscillator potential.Comment: 23p, TIFR-TH-93/05; (v3) tex error correcte

Probing Type I' String Theory Using D0 and D4-Branes

We analyse the velocity-dependent potentials seen by D0 and D4-brane probes moving in Type I' background for head-on scattering off the fixed planes. We find that at short distances (compared to string length) the D0-brane probe has a nontrivial moduli space metric, in agreement with the prediction of Type I' matrix model; however, at large distances it is modified by massive open strings to a flat metric, which is consistent with the spacetime equations of motion of Type I' theory. We discuss the implication of this result for the matrix model proposal for M-theory. We also find that the nontrivial metric at short distances in the moduli space action of the D0-brane probe is reflected in the coefficient of the higher dimensional v^4 term in the D4-brane probe action.Comment: 12 pages, latex. References added and some typos correcte

Classical Fermi Fluid and Geometric Action for c=1c=1

We formulate the $c=1$ matrix model as a quantum fluid and discuss its classical limit in detail, emphasizing the $\hbar$ corrections. We view the fermi fluid profiles as elements of \winf-coadjoint orbit and write down a geometric action for the classical phase space. In the specific representation of fluid profiles as `strings' the action is written in a four-dimensional form in terms of gauge fields built out of the embedding of the `string' in the phase plane. We show that the collective field action can be derived from the above action provided one restricts to quadratic fluid profiles and ignores the dynamics of their `turning points'.Comment: 31 pages. (Revised version

Renormalization group flows in a Lifshitz-like four fermi model

We study renormalization group flows in the Lifshitz-like $N$-flavour four fermi model discussed in 0905.2928. In the large-$N$ limit, a nontrivial flow occurs in only one of all possible marginal couplings and one relevant coupling, which provides the scale for Lorentz invariance violations. We discuss in detail the phase diagram and RG flows in the space of couplings, which includes the Lifshitz fixed point, the free field fixed point and a new fixed point characterized by $z=1$ scaling and a violation of Lorentz invariance, which cannot be tuned away by adjusting a parameter. In the broken symmetry phase, the model flows from the $z=3$ Lifshitz-like fixed point in the ultraviolet to this new fixed point in the infrared. However, in a modified version of the present model, which has an effective ultraviolet cut-off much smaller than the Lorentz invariance violating scale, the infrared behaviour is governed by an approximately Lorentz invariant theory, similar to the low energy limit of the usual relativistic Nambu$-$Jona-Lasinio model. Such a modified model could be realized by a supersymmetric version of the present model.Comment: 30 pages, 2 figure