Publications (11)50.4 Total impact
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ABSTRACT: Electric fields may decay by quantum tunneling: as calculated by Schwinger, an electronpositron pair may be summoned from the vacuum. In this paper I calculate the pairproduction rate at nonzero temperatures. I find that at high temperatures the decay rate is dominated by a new instanton that involves both thermal fluctuation and quantum tunneling; this decay is exponentially faster than the rate in the literature. I also calculate the decay rate when the electric field wraps a compact circle (at zero temperature). The same new instanton also governs this rate: I find that for small circles decay is dominated by a process that drops the electric field by one unit, but does not produce charged particles. 
Article: The decay of hot KK space
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ABSTRACT: The nonperturbative instabilities of hot KaluzaKlein spacetime are investigated. In addition to the known instability of hot space (the nucleation of 4D black holes) and the known instability of KK space (the nucleation of bubbles of nothing by quantum tunneling), we find two new instabilities: the nucleation of 5D black holes, and the nucleation of bubbles of nothing by thermal fluctuation. These four instabilities are controlled by two Euclidean instantons, with each instanton doing double duty via two inequivalent analytic continuations; thermodynamic instabilities of one are shown to be related to mechanical instabilities of the other. I also construct bubbles of nothing that are formed by a hybrid process involving both thermal fluctuation and quantum tunneling. There is an exact hightemperature/lowtemperature duality that relates the nucleation of black holes to the nucleation of bubbles of nothing. 
Article: Flux Compactifications on $(S_2)^N$
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ABSTRACT: We investigate a simple extradimensional model and its fourdimensional vacua. This model has a twoform flux and a positive cosmological constant, and the extra dimensions are compactified as the product of $N$ twospheres. The theory is an interesting laboratory because it is at once simple enough to be soluble but rich enough to exhibit many features not present in previous model landscapes.  [Show abstract] [Hide abstract]
ABSTRACT: We study compactifications of $D$dimensional de Sitter space with a $q$form flux down to $DNq$ dimensions. We show that for $(N1)(q1)\geq 2$ there are doubleexponentially or even infinitely many compact de Sitter vacua, and that their effective cosmological constants accumulate at zero. This population explosion of $\Lambda \ll 1$ de Sitters arises by a mechanism analogous to natural selection.  [Show abstract] [Hide abstract]
ABSTRACT: We study the spectrum and perturbative stability of FreundRubin compactifications on $M_p \times M_{Nq}$, where $M_{Nq}$ is itself a product of $N$ $q$dimensional Einstein manifolds. The higherdimensional action has a cosmological term $\Lambda$ and a $q$form flux, which individually wraps each element of the product; the extended dimensions $M_p$ can be antide Sitter, Minkowski, or de Sitter. We find the masses of every excitation around this background, as well as the conditions under which these solutions are stable. This generalizes previous work on FreundRubin vacua, which focused on the $N=1$ case, in which a $q$form flux wraps a single $q$dimensional Einstein manifold. The $N=1$ case can have a classical instability when the $q$dimensional internal manifold is a productone of the members of the product wants to shrink while the rest of the manifold expands. Here, we will see that individually wrapping each element of the product with a lowerform flux cures this cyclecollapse instability. The $N=1$ case can also have an instability when $\Lambda>0$ and $q\ge4$ to shapemode perturbations; we find the same instability in compactifications with general $N$, and show that it even extends to cases where $\Lambda\le0$. On the other hand, when $q=2$ or 3, the shape modes are always stable and there is a broad class of AdS and de Sitter vacua that are perturbatively stable to all fluctuations.  [Show abstract] [Hide abstract]
ABSTRACT: Nothing—the absence of spacetime—can be either an endpoint of tunneling, as in the bubble of nothing, or a starting point for tunneling, as in the quantum creation of a universe. We argue that these two tunnelings can be treated within a unified framework, and that, in both cases, nothing should be thought of as the limit of antide Sitter space in which the curvature length approaches zero. To study nothing, we study decays in models with perturbatively stabilized extra dimensions, which admit not just bubbles of nothing—topologychanging transitions in which the extra dimensions pinch off and a hole forms in spacetime—but also a whole family of topologypreserving transitions that nonetheless smoothly hollow out and approach the bubble of nothing in one limit. The bubble solutions that are close to this limit, bubbles of nexttonothing, give us a controlled setting in which to understand nothing. Armed with this understanding, we are able to embed proposed mechanisms for the reverse process, tunneling from nothing to something, within the relatively secure foundation of the ColemanDe Luccia formalism and show that the HawkingTurok instanton does not mediate the quantum creation of a universe. 
Article: Populating the Whole Landscape
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ABSTRACT: Every de Sitter vacuum can transition to every other de Sitter vacuum despite any obstacle, despite intervening antide Sitter sinks, despite not being connected by an instanton. Eternal inflation populates the whole landscape.  [Show abstract] [Hide abstract]
ABSTRACT: There is a standard story about decay in multidimensional flux landscapes: that from any state, the fastest decay is to take a small step, discharging one flux unit at a time; that fluxes with the same coupling constant are interchangeable; and that states with N units of a given flux have the same decay rate as those with N. We show that this standard story is false. The fastest decay is a giant leap that discharges many different fluxes in unison; this decay is mediated by a “minimal” brane that wraps the internal manifold and exhibits behavior not visible in the effective theory. We discuss the implications for the cosmological constant problem.  [Show abstract] [Hide abstract]
ABSTRACT: Instantons are tunneling solutions that connect two vacua, and under a small change in the potential, instantons sometimes disappear. We classify these disappearances as smooth (decay rate goes to 0 at disappearance) or abrupt (decay rate not equal to 0 at disappearance). Abrupt disappearances mean that a small change in the parameters can produce a drastic change in the physics, as some states become suddenly unreachable. The simplest abrupt disappearances are associated with annihilation by another Euclidean solution with higher action and one more negative mode; higherorder catastrophes can occur in cases of enhanced symmetry. We study a few simple examples, including the 6D EinsteinMaxwell theory, and give a unified account of instanton disappearances.  [Show abstract] [Hide abstract]
ABSTRACT: The rate and manner of vacuum decay are calculated in an explicit flux compactification, including all thickwall and gravitational effects. For landscapes built of many units of a single flux, the fastest decay is usually to discharge just one unit. By contrast, for landscapes built of a single unit each of many different fluxes, the fastest decay is usually to discharge all the flux at once, which destabilizes the radion and begets a bubble of nothing. By constructing the bubble of nothing as the limit in which ever more flux is removed, we gain new insight into the bubble's appearance. Finally, we describe a new instanton that mediates simultaneous flux tunneling and decompactification. Our model is the thinbrane approximation to sixdimensional EinsteinMaxwell theory.  [Show abstract] [Hide abstract]
ABSTRACT: For landscapes of field theory vacua, we identify an effect that can greatly enhance the decay rates to wildly distant minimaso much so that such transitions may dominate over transitions to near neighbors. We exhibit these 'giant leaps' in both a toy twofield model and, in the thinwall approximation, amongst the fourdimensional vacua of 6D EinsteinMaxwell theory, and it is argued that they are generic to landscapes arising from flux compactifications. We discuss the implications for the cosmological constant and the stability of stringy de Sitter. Comment: 23 pages, 12 figures
Publication Stats
91  Citations  
50.40  Total Impact Points  
Top Journals
Institutions

20132014

Stanford University
 Department of Physics
Palo Alto, California, United States


20102012

Princeton University
 Department of Physics
Princeton, NJ, United States
