Abstract
Using a holographic model, we study quantum field theories with a layer of one CFT surrounded by another CFT, on either a periodic or an infinite direction. We study the vacuum energy density in each CFT as a function of the central charges, the thickness of the layer(s), and the properties of the interfaces between the CFTs. The dual spacetimes in the holographic model include two regions separated by a dynamical interface with some tension. For two or more spatial dimensions, we find that a layer of CFT with more degrees of freedom than the surrounding one can have an anomalously large negative vacuum energy density for certain types of interfaces. The negative energy density (or null-energy density in the direction perpendicular to the interface) becomes arbitrarily large for fixed layer width when the tension of the bulk interface approaches a lower critical value. We argue that in cases where we have large negative energy density, we also have an anomalously high transition temperature to the high-temperature thermal state.
Highlights
We can consider such a CFT on Rd−2,1 times a strip of width w in the z direction with various choices of boundary physics or couplings between the two sides of the strip
For a given u we find that solutions with a connected interface exist up to some critical value e∗(u) = e∗(1/u)
We have made use of a holographic model for interface CFTs to demonstrate a surprising enhancement of negative vacuum energy for a CFT on a strip
Summary
We consider quantum field theories built from one or more CFTs, where CFTi lives on Rd−2,1 times an interval of width wi. At the boundaries of these intervals, the CFTs may be joined to another CFT via a conformal interface, or we may have a conformal boundary theory.. We refer to the direction along the various intervals as z and use Greek indices to refer to the Rd−2,1 directions. Assuming that the vacuum state preserves the geometrical (d − 2) + 1 dimensional Poincaré symmetry, the stress-energy tensor in each CFT must take the form. The stress-energy tensor must be traceless, so we have that (d−1)f = −g. The constant Fi can depend only on the dimensionless ratios between wis, together with our choice of CFTs and interfaces. Our goal in this paper is to understand the behavior of Fi as a function of the wis in various cases and in particular to understand how large Fi can be
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