dorsal/arxiv
View SchemaEffect of the Vacuum Energy Density on Graviton Propagation
| Authors | Giovanni Modanese, Giorgio Fontana |
|---|---|
| Categories | |
| ArXiv ID | physics/0409098 |
| URL | https://arxiv.org/abs/physics/0409098 |
| DOI | 10.1063/1.1649691 |
Abstract
It is known that the value L of the vacuum energy density affects the propagation equation for gravitons: A mass term appears in the propagation equation, such that m^2=-L. As a consequence, the polarization states of gravitons also change. This effect of the L-term has been confirmed by recent calculations in a curved background, which is the only proper setting, since solutions of the classical Einstein equations in the presence of a L-term represent a space with constant curvature. A real value for the mass (when L<0) will show up as a slight exponential damping in the gravitational potential, which is however strongly constrained by astronomical data. The consequences of an imaginary mass (for L>0) are still unclear; on general grounds, one can expect the onset of instabilities in this case. This is also confirmed by numerical simulations of quantum gravity which became recently available. These properties gain a special interest in consideration of the following. (1) The most recent cosmological data indicate that L is positive and of the order of 0.1 J/m^3. Is this value compatible with a stable propagation of gravitons? (2) The answer to the previous question lies perhaps in the scale dependence of the effective value of L. L may be negative at the small distance/large energy scale at which the quantum behavior of gravitational fields and waves becomes relevant. Furthermore, local contributions to the vacuum energy density (in superconductors in certain states, and in very strong static electromagnetic fields) can change locally the sign of L, and so affect locally the propagation and the properties of gravitons. The graviton wavefunction, for different values of the parameters, may be characterized by superluminal phase velocity or by unitarity only in imaginary valued time.
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"abstract": "It is known that the value L of the vacuum energy density affects the\npropagation equation for gravitons: A mass term appears in the propagation\nequation, such that m^2=-L. As a consequence, the polarization states of\ngravitons also change. This effect of the L-term has been confirmed by recent\ncalculations in a curved background, which is the only proper setting, since\nsolutions of the classical Einstein equations in the presence of a L-term\nrepresent a space with constant curvature. A real value for the mass (when L\u003c0)\nwill show up as a slight exponential damping in the gravitational potential,\nwhich is however strongly constrained by astronomical data. The consequences of\nan imaginary mass (for L\u003e0) are still unclear; on general grounds, one can\nexpect the onset of instabilities in this case. This is also confirmed by\nnumerical simulations of quantum gravity which became recently available. These\nproperties gain a special interest in consideration of the following. (1) The\nmost recent cosmological data indicate that L is positive and of the order of\n0.1 J/m^3. Is this value compatible with a stable propagation of gravitons? (2)\nThe answer to the previous question lies perhaps in the scale dependence of the\neffective value of L. L may be negative at the small distance/large energy\nscale at which the quantum behavior of gravitational fields and waves becomes\nrelevant. Furthermore, local contributions to the vacuum energy density (in\nsuperconductors in certain states, and in very strong static electromagnetic\nfields) can change locally the sign of L, and so affect locally the propagation\nand the properties of gravitons. The graviton wavefunction, for different\nvalues of the parameters, may be characterized by superluminal phase velocity\nor by unitarity only in imaginary valued time.",
"arxiv_id": "physics/0409098",
"authors": [
"Giovanni Modanese",
"Giorgio Fontana"
],
"categories": [
"physics.gen-ph"
],
"doi": "10.1063/1.1649691",
"title": "Effect of the Vacuum Energy Density on Graviton Propagation",
"url": "https://arxiv.org/abs/physics/0409098"
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