Dispatches form the color line: The press and multiracial America - by Catherine R. Squires

Woodard, Jennifer

doi:10.1111/j.1460-2466.2007.00380_4.x

Cited by 3 publications

(3 citation statements)

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“…However, no energy is needed to excite a negative energy mode, since the decay happens through simultaneous emission of ghost modes and healthy modes at fixed total energy. Therefore a ghost does not decouple when its mass is higher than the cut-off, actually it couples more strongly since (from the point of view of the energy) it is more effective in exciting the healthy modes [12,18].…”

Section: Ghosts In Effective Theoriesmentioning

confidence: 99%

Classical and quantum ghosts

Sbisà¹

2014

Eur. J. Phys.

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The aim of these notes is to provide a self-contained review of why it is generically a problem when a solution of a theory possesses ghost fields among the perturbation modes. We define what a ghost field is and we show that its presence is associated to a classical instability whenever the ghost field interacts with standard fields. We then show that the instability is more severe at quantum level, and that perturbative ghosts can exist only in low energy effective theories. However, if we don't consider very ad-hoc choices, compatibility with observational constraints implies that low energy effective ghosts can exist only at the price of giving up Lorentz-invariance or locality above the cut-off, in which case the cut-off has to be much lower that the energy scales we currently probe in particle colliders. We also comment on the possible role of extra degrees of freedom which break Lorentz-invariance spontaneously.

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Section: Ghosts In Effective Theoriesmentioning

confidence: 99%

Classical and quantum ghosts

Sbisà¹

2014

Eur. J. Phys.

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“…The electroweak theory is actually weakly coupled, therefore, it is unlikely that the corresponding almost non-interacting heavy degrees of freedom contribute to the vacuum energy with the definition for it stated above. Notice that covariance seem to require that, holding on to the de Sitter example for definiteness, only even powers of H have right to enter the expression for the vacuum energy [23]; this may however be not true [24].…”

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confidence: 99%

Cosmological constant from the ghost: A toy model

2009

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We suggest that the solution to the cosmological vacuum energy puzzle is linked to the infrared sector of the effective theory of gravity interacting with standard model fields. We propose a specific solvable two dimensional model where our proposal can be explicitly tested. We analyse the 2d Schwinger model on a 2-torus and in curved 2d space, mostly exploiting the properties of its topological susceptibility, its links with the non-trivial topology or deviations from spacetime flatness, and its relations to the real 4d world. The Kogut-Susskind ghost (which is a direct analogue of the Veneziano ghost in 4d) on a 2-torus and in curved 2d space plays a crucial rôle in the computation of the vacuum energy. The departure from Minkowski flatness, which is defined as the cosmological constant in our framework, is found to scale as 1/L, where L is the linear size of the torus. Therefore, in spite of the fact that the physical sector of 2d QED is represented by a single massive scalar particle, the deviation from Minkowski space is linear in L rather than exponentially suppressed as one could naïvely expect.

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“…and shows that this is a spacetime of constant curvature, therefore de Sitter. Richard Woodard [16] has confirmed this by showing that the metric ( 18) can be reduced to the familiar static deSitter metric by the coordinate change…”

Section: Background Spacetimementioning

confidence: 87%

Hyperboloidal Slices and Artificial Cosmology for Numerical Relativity

Misner

2006

Deserfest

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This preliminary report proposes integrating the Maxwell equations in Minkowski spacetime using coordinates where the spacelike surfaces are hyperboloids asymptotic to null cones at spatial infinity. The space coordinates are chosen so that Scri+ occurs at a finite coordinate and a smooth extension beyond Scri+ is obtained. The question addressed is whether a Cauchy evolution numerical integration program can be easily modified to compute this evolution. In the spirit of the von Neumann and Richtmyer artificial viscosity which thickens a shock by many orders of magnitude to facilitate numerical simulation, I propose artificial cosmology to thicken null infinity Scri+ to approximate it by a de Sitter cosmological horizon where, in conformally compactified presentation, it provides a shell of purely outgoing null cones where asymptotic waves can be read off as data on a spacelike pure outflow outer boundary. This should be simpler than finding Scri+ as an isolated null boundary or imposing outgoing wave conditions at a timelike boundary at finite radius.It is a pleasure to dedicate this work to my friend and colleague Stanley Deser as we celebrate his ancient works and his continuing contributions to a broad variety of problems in physics.

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Dispatches form the color line: The press and multiracial America - by Catherine R. Squires

Cited by 3 publications

References 0 publications

Classical and quantum ghosts

Classical and quantum ghosts

Cosmological constant from the ghost: A toy model

Hyperboloidal Slices and Artificial Cosmology for Numerical Relativity

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