Vacuum Energy

We develop a geometro-dynamical approach to the cosmological constant problem (CCP) by invoking a geometry induced by the energy-momentum tensor of vacuum, matter and radiation. The construction, which utilizes the dual role of the metric tensor that it structures both the spacetime manifold and energy-momentum tensor of the vacuum, gives rise to a framework in which the vacuum energy induced by matter and radiation, instead of gravitating, facilitates the generation of the g...

It is argued that the zero-point energies of free quantum fields diverge at most quadratically and not quartically, as is generally believed. This is a consequence of the relativistic invariance which requires that the energy density of the vacuum $\rho$ and its pressure $p$ satisfy $\rho=-p$. The usually obtained quartic divergence is an artifact of the use of a noninvariant regularization which violates this relation. One consequence of our results is that the zero-point en...

Possible analogies between vacuum state and quantum fluid provide a model to study vacuum energy density induced by thermal corrections, space-time curvature, boundary conditions and quantum back-reaction. We find that vacuum energy density in this quantum fluid model is not naturally of the order of the matter energy density. We show how higher-order corrections in quantum back-reaction can also contribute to vacuum energy density, and how the cosmological expansion is a man...

The equations of motion for matter fields are invariant under the shift of the matter lagrangian by a constant. Such a shift changes the energy momentum tensor of matter by T^a_b --> T^a_b +\rho \delta^a_b. In the conventional approach, gravity breaks this symmetry and the gravitational field equations are not invariant under such a shift of the energy momentum tensor. I argue that until this symmetry is restored, one cannot obtain a satisfactory solution to the cosmological ...

The cosmological constant (CC) term in Einstein's equations, Lambda, was first associated to the idea of vacuum energy density. Notwithstanding, it is well-known that there is a huge, in fact appalling, discrepancy between the theoretical prediction and the observed value picked from the modern cosmological data. This is the famous, and extremely difficult, "CC problem". Paradoxically, the recent observation at the CERN Large Hadron Collider of a Higgs-like particle, should a...

The cosmological constant problem is reviewed and a possible quantum gravity resolution is proposed. A space satellite E\"otv\"os experiment for zero-point vacuum energy is proposed to see whether Casimir vacuum energy falls in a gravitational field at the same rate as ordinary matter.

The discussion of vacuum energy is currently a subject of great theoretical importance, specially concerning the cosmological constant problem in General Relativity. From Quantum Field Theory, it is stated that vacuum states subject to boundary conditions may generate tensions on these boundaries related to a measurable non-zero renormalized vacuum energy: the Casimir Effect. As such, investigating how these vacuum states and energy behave in curved backgrounds is just natura...

Considering the fundamental cutoff applied by the uncertainty relations' limit on virtual particles' frequency in the quantum vacuum, it is shown that the vacuum energy density is proportional to the inverse of the forth power of the dimensional distance of the space under consideration and thus the corresponding vacuum energy automatically regularized to zero value for an infinitely large free space. This can be used in regularizing a number of unwanted infinities happen in ...

The phenomenon of emergent physics in condensed-matter many-body systems has become the paradigm of modern physics, and can probably also be applied to high-energy physics and cosmology. This encouraging fact comes from the universal properties of the ground state (the analog of the quantum vacuum) in fermionic many-body systems, described in terms of the momentum-space topology. In one of the two generic universality classes of fermionic quantum vacua the gauge fields, chira...

We explore two hypotheses. First, the possibility that the quantum vacuum energy density of the Casimir effect contributes to a (local) gravitational vacuum energy density. Second, the possibility that a change in the gravitational coupling implies a change in the cosmological constant. We parametrize these two possibilities in a covariant framework and show that the next generation of Casimir experiments does have a surprisingly good chance of exploring this parameter space.