Wavefunction Collapse in String Theory

Abstract

One of the most intriguing proposals for wavefunction collapse is the Diosi Penrose model, in which collapse is driven by stochastic fluctuations of the Newtonian potential. We argue that a closely related effective structure can emerge in string theory if, as recently suggested, the present cosmic acceleration is sourced by instant folded strings and their decay products. A key difference, however, is that in this stringy setting the noise is naturally colored in time rather than white. As a result, the scenario is significantly less constrained by existing experiments than the standard Diosi Penrose model.

Figures (3)

• Figure 1: Decoherence approximately diagonalizes the density matrix. In the many-worlds approach, this is the end of the story: the different branches persist without further collapse. In objective collapse models, by contrast, an additional non-unitary evolution selects one definite outcome.
• Figure 2: Toy dipole models. The green line represents the positive energy particle, and the red line the negative energy particle. Panel (a) reproduces the DP spatial dependence, $1/k^2$, but does not yield approximately white noise in time. Panels (b) and (c) do. Panel (c) provides a good approximation to the stringy model discussed in the next section.
• Figure 3: (a) An instant folded string is created classically at a point and subsequently expands at the speed of light, with its total energy remaining zero. (b) Quantum mechanically, an instant folded string splits. Because its total energy is zero, the decay produces an energy-EPR state that behaves as an expanding dipole originating at the splitting point. In this example, the left-moving string carries positive energy, while the right-moving string carries negative energy, so the net energy remains zero.