arXiv subjects

Joanna L. Karczmarek

Publications and source records attributed to Joanna L. Karczmarek.

30 records · Page 2Linked to original sources

arXiv2005

Spacelike boundaries from the c=1 Matrix Model

We find classical solutions of two dimensional noncritical string theory which give rise to geometries with spacelike boundaries, similar to spacetimes with cosmological event horizons. In the c=1 matrix model, these solutions have a representation as simple time dependent configurations. We obtain the causal structure of the resulting spacetimes. Using the macroscopic loop transform, we probe the form of the tachyon condensate in the asymptotic regions.

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arXiv2004

Black Hole Non-Formation in the Matrix Model

The leading classical low-energy effective actions for two-dimensional string theories have solutions describing the gravitational collapse of shells of matter into a black hole. It is shown that string loop corrections can be made arbitrarily small up to the horizon, but $α'$ corrections cannot. The matrix model is used to show that typical collapsing shells do not form black holes in the full string theory. Rather, they backscatter out to infinity just before the horizon forms. The matrix model is also used to show that the naively expected particle production induced by the collapsing shell vanishes to leading order. This agrees with the string theory computation. From the point of view of the effective low energy field theory this result is surprising and involves a delicate cancellation between various terms.

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arXiv2004

Multicore Noncommutative Bions

The noncommutative bion core of Constable, Myers and Tafjord (hep-th/9911136) describes the BPS D1-D3 brane intersection (where a single bundle of D1-branes is attached to the D3 brane) in the nonabelian Born-Infeld theory of D1-branes. The possibility of extending this construction to BPS configurations with multiple separated parallel bundles of D1-branes attached to a single D3-brane is discussed. The problem is reduced to solving the Nahm equation with novel boundary conditions. A concrete, non-trivial solution is presented.

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arXiv2004

Collective Field Description of Matrix Cosmologies

We study the Das-Jevicki collective field description of arbitrary classical solutions in the c=1 matrix model, which are believed to describe nontrivial spacetime backgrounds in 2d string theory. Our analysis naturally includes the case of a Fermi droplet cosmology: a finite size droplet of Fermi fluid, made up of a finite number of eigenvalues. We analyze properties of the coordinates in which the metric in the collective field theory is trivial, and comment on the form of the interaction terms in these coordinates.

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arXiv2004

Closed String Tachyon Condensation at c=1

The c=1 matrix model, with or without a type 0 hat, has an exact quantum solution corresponding to closed string tachyon condensation along a null surface. The condensation occurs, and spacetime dissolves, at a finite retarded time on I^+. The outgoing quantum state of tachyon fluctuations in this time-dependent background is computed using both the collective field and exact fermion pictures. Perturbative particle production induced by the moving tachyon wall is shown to be similar to that induced by a soft moving mirror. Hence, despite the fact that I^+ for the tachyon is geodesicaly incomplete, quantum correlations in the incoming state are unitarily transmitted to the outgoing state in perturbation theory. It is also shown that, non-perturbatively, information can leak across the tachyon wall, and tachyon scattering is not unitary. Exact unitarity remains intact only in the free fermion picture.

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arXiv2004

Hartle-Hawking Vacuum for c=1 Tachyon Condensation

Quantum vacua are constructed for a time-symmetric cosmology describing closed string tachyon condensation in two-dimensional string theory. Due to the Euclidean periodicity of the solution, and despite its time dependence, we are able to construct thermal states at discrete values of the temperature. The asymptotic thermal Green functions and stress energy tensor are computed and found to have an intriguing resemblance to those in the Hartle-Hawking vacuum of a black hole.

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arXiv2003

Matrix Cosmology

Exact time-dependent solutions of c=1 string theory are described using the free fermion formulation. One such class of solutions describes draining of the Fermi sea and has a spacetime interpretation as closed string tachyon condensation. A second class of solutions, corresponding to droplets of Fermi liquid orbiting in phase space, describes closed cosmologies which bounce through singularities.

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arXiv2003

UV Finite Brane Decay

The decay of an unstable D-brane via closed string emission and open string pair production is considered in subcritical string theory with a spacelike linear dilaton. The decay rate is given by the imaginary part of the annulus, which has ambiguities corresponding to the choices of incoming closed and open string vacua. An exact expression for the full annulus diagram is computed with a natural choice of incoming vacua. It is found that the ultraviolet divergences present in critical string theory in both of these processes are absent for any nonzero spacelike dilaton. Implications for the vexing issue of the tachyon dust are discussed.

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arXiv2002

Tilting the Noncommutative Bion

In this note, we extend the noncommutative bion core solution of Constable, Myers and Tafjord (hep-th/9911136) to include the effects of a nonzero NS-NS two-form B. The result is a `tilted bion' in which the core expands out to a single D3-brane at an angle to the D1-brane core. Its properties agree perfectly with an analysis of the dual situation, that of a magnetic charge on an abelian D3-brane in a background worldvolume magnetic field. We also demonstrate that this agreement extends beyond geometry to include the field strength on the D3-brane. We make a proposal for including possible worldvolume gauge fields when mapping a noncommutative geometrical brane solution onto a corresponding commutative brane description.

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arXiv2001

Nonlocal Field Theories and their Gravity Duals

The gravity duals of nonlocal field theories in the large N limit exhibit a novel behavior near the boundary. To explore this, we present and study the duals of dipole theories - a particular class of nonlocal theories with fundamental dipole fields. The nonlocal interactions are manifest in the metric of the gravity dual and type-0 string theories make a surprising appearance. We compare the situation to that in noncommutative SYM.

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arXiv2001

A Note on Intersecting and Fluctuating Solitons in 4D Noncommutative Field Theory

We examine the intersections, fluctuations and deformations of codimension two solitons in field theory on noncommutative $R^4$, in the limit of large noncommutativity. We find that holomorphic deformations are zero modes of flat branes, and we show that there is a zero mode localized at the intersection of two solitons.

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arXiv2000

M(atrix)-Theory Scattering in the Noncommutative (2,0) theory

We study the Quantum-Mechanics on the hyper-Kahler manifold that is the blow-up of an $A_1$-singularity. This system is relevant for M(atrix)-theory as it was conjectured to describe scattering in the "noncommutative" deformation of a free 5+1D tensor multiplet in the sector with two units of longitudinal light-like momentum.

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