Vacuum energy

Summary

Vacuum energy is an underlying background energy that exists in space throughout the entire Universe. The vacuum energy is a special case of zero-point energy that relates to the quantum vacuum. The effects of vacuum energy can be experimentally observed in various phenomena such as spontaneous emission, the Casimir effect and the Lamb shift, and are thought to influence the behavior of the Universe on cosmological scales. Using the upper limit of the cosmological constant, the vacuum energy of free space has been estimated to be 10−9 joules (10−2 ergs), or ~5 GeV per cubic meter. However, in quantum electrodynamics, consistency with the principle of Lorentz covariance and with the magnitude of the Planck constant suggests a much larger value of 10113 joules per cubic meter. This huge discrepancy is known as the cosmological constant problem or, colloquially, the "vacuum catastrophe." Origin Quantum field theory states that all fundamental fields, such as the electromagneti

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Spontaneous conformal symmetry breaking in fishnet CFT

Georgios Karananas

Quantum field theories with exact but spontaneously broken conformal invariance have an intriguing feature: their vacuum energy (cosmological constant) is equal to zero. Up to now, the only known ultraviolet complete theories where conformal symmetry can be spontaneously broken were associated with supersymmetry (SUSY), with the most prominent example being the N=4 SUSY Yang-Mills. In this Letter we show that the recently proposed conformal "fishnet" theory supports at the classical level a rich set of flat directions (moduli) along which conformal symmetry is spontaneously broken. We demonstrate that, at least perturbatively, some of these vacua survive in the full quantum theory (in the planar limit, at the leading order of 1/N-c expansion) without any fine tuning. The vacuum energy is equal to zero along these flat directions, providing the first non-SUSY example of a four-dimensional quantum field theory with "natural" breaking of conformal symmetry. (C) 2020 The Authors. Published by Elsevier B.V.

ELSEVIER2020

We have studied the evolution of the Pt(111) Shockley-type surface state, which can be described as a surface resonance upon deposition of Ag monolayers. We have combined angle-resolved photoemission and scanning-tunneling-spectroscopy measurements with electronic-structure and photoemission calculations for true semi-infinite systems to guarantee a complete description of all surface-sensitive spectral features. An unusual energy shift and a considerable Rashba-type spin-orbit splitting of the surface resonance were observed and are discussed in terms of modifications in the electronic structure and relationship between the semi-infinite bulk and the surface potential via multiple electron scattering. The maximum magnitude of the splitting in momentum space amounts to 0.051 ± 0.007 °A−1 and appears as one of the highest values so far observed in the Gamma-type surface-state-resonance bands.

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Connection between diphoton and triboson channels in new physics searches

Kyrylo Bondarenko, Alexey Boyarsky, Lesya Shchutska

Diphoton channel provides a clean signature in searches for new physics. In this paper, we discuss a connection between the diphoton channel ( γγ ) and triboson channels ( Zγγ , ZZγ , WWγ ) imposed by the SU(2)L×U(1)Y symmetry of the Standard Model (SM) in certain classes of models. To illustrate this idea we choose a simple model that has all these channels. In this model, the same physics can give rise to γ+MET instead of γγ and 2 bosons plus missing energy instead of 3-boson channels. We analyze existing constraints and previous searches and show that channels WWγ and especially Zγ+MET have a potential to discover new physics at the LHC.

2018