International Journal of Modern Physics A

We discuss the scattering of a light closed-string state off a D-brane, taking into account quantum recoil effects on the latter, which are described by a pair of logarithmic operators. The light particle and D-brane subsystems may each be described by a world sheet with an external source due to the interaction between them. This perturbs each subsystem away from criticality, which is compensated by dressing with a Liouville field whose zero mode we interpret as time. The resulting evolution equations for the D-brane and the closed string are of Fokker–Planck and modified quantum Liouville type, respectively. The apparent entropy of each subsystem increases as a result of the interaction between them, which we interpret as the loss of information resulting from nonobservation of the other entangled subsystem. We speculate on the possible implications of these results for the propagation of closed strings through a dilute gas of virtual D-branes.

We describe heavy baryons as bound states of a quark and a diquark. For this purpose we derive the Faddeev equation for baryons containing a single heavy quark from a Nambu–Jona–Lasinio type of model which is appropriately extended to include also heavy quarks. The latter are treated in the heavy mass limit. The heavy baryon Faddeev equation is then solved using a static approximation for the exchanged quark.

An example of a supersymmetric model involving two interacting chiral superfields is presented here which allows for solutions describing stringlike "domain ribbon" defects embedded within a domain wall. It is energetically favorable for the fermions within the wall to populate the domain ribbons, and an explicit solution is found for the fermion zero modes. The Fermi gas within ribbons can allow them to stabilize in the form of small loops.

An ℏ-deformed Virasoro Poisson algebra is obtained using the Wakimoto realization of the Sugawara operator for the Yangian double DY_ℏ(sl₂)_c at the critical level c=-2.

The most relevant thermal perturbation of the continuous d=2 minimal conformal theory with c=7/10 (Tricritical Ising Model) is treated here. This model describes the scaling region of the ϕ⁶ universality class near the tricritical point. The problematic IR divergences of the naive perturbative expansion around conformal theories are dealt within the OPE approach developed at all orders by the authors. The main result is a description of the short distance behavior of correlators that is compared with existing long distance expansion (form factors approach) related to the integrability of the model.

In a one-dimensional lattice, the induced metric (from a noncommutative geometry calculation) breaks translation invariance. This leads to some inconsistencies among different spectator frames, in the observation of the hoppings of a test particle between lattice sites. To resolve the inconsistencies between the different spectator frames, we replace the test particle's bare mass by an effective locally dependent mass. This effective mass also depends on the lattice constant — i.e. it a scale dependent variable (a "running" mass).

We also develop an alternative approach based on a compensating potential. The induced potential between a spectator frame and the test particle is attractive on the average.

We then show that the entire formalism holds for a quantum particle represented by a wave function, just as it applies to the mechanics of a classical point particle.

We use path-integral methods to analyze the vacuum properties of a recently proposed extension of the Thirring model in which the interaction between fermionic currents is nonlocal. We calculate the exact ground state wave functional of the model for any bilocal potential, and also study its long-distance behavior. We show that the ground state wave functional has a general factored Jastrow form. We also find that it possesses an interesting symmetry involving the interchange of density–density and current–current interactions.

We speculate about the space–time description due to the presence of Lorentzian worm-holes (handles in space–time joining two distant regions or other universes) in quantum gravity. The semiclassical rate of production of these Lorentzian wormholes in Reissner–Nordström space–times is calculated as a result of the spontaneous decay of vacuum due to a real tunneling configuration. In the magnetic case it only depends on the value of the field theoretical fine structure constant. We predict that the quantum probability corresponding to the nucleation of such geodesically complete space–times should be acutally negligible in our physical Universe.