Related papers: Evidence for a Cosmological Phase Transition on th…
It is known that the unregularized expressions for the stress-energy tensor components corresponding to subhorizon and superhorizon vacuum fluctuations of a massless scalar field in a Friedmann-Robertson-Walker background are characterized…
By taking seriously the limits on observability which come from combining relativistic quantum mechanics with general relativity, Ed Jones has shown that the current measurements of the cosmological constant density $\Omega_{\Lambda}\sim…
Using a static massive spherically symmetric scalar field coupled to gravity in the Schwarzschild-de Sitter (SdS) background, first we consider some asymptotic solutions near horizon and their local equations of state(E.O.S) on them. We…
The Swampland program, which looks for low energy theories consistent with quantum gravity, has led to the introduction of a dark dimension stemming from the cosmological constant. We show that the same argument leads to the emergence of…
The theory of cosmological fluctuations assumes that the pre-inflationary state of the universe was the quantum vacuum of a scalar field(s) coupled to gravity. The observed cosmic microwave background fluctuations are then interpreted as…
Vacuum energy changes during cosmological phase transitions and becomes relatively important at epochs just before phase transitions. For a viable cosmology the vacuum energy just after a phase transition must be set by the critical…
A phenomenological model of dark energy that tracks the baryonic and cold dark matter at early times but resembles a cosmological constant at late times is explored. In the transition between these two regimes, the dark energy density drops…
Accepting the fine tuned cosmological constant hypothesis, we have recently proposed that this hypothesis can be tested if the dark matter freeze out occurs at the electroweak scale and if one were to measure an anomalous shift in the dark…
Nearly conformal dynamics at the TeV scale as motivated by the hierarchy problem can be characterized by a stage of significant supercooling at the electroweak epoch. This has important cosmological consequences. In particular, a common…
We study the cosmology with the running dark energy. The parametrization of dark energy with the respect to the redshift is derived from the first principles of quantum mechanics. Energy density of dark energy is obtained from the quantum…
A hypothetical dark energy component may have an equation of state that is different from a cosmological constant and possibly even changing in time. The spacing of the cosmic microwave background peaks is sensitive to the ratio of the…
We discuss from the condensed-matter point of view the recent idea that the Poisson fluctuations of cosmological constant about zero could be a source of the observed dark energy. We argue that the thermodynamic fluctuations of Lambda are…
The traditional "explanation" for the observed acceleration of the universe is the existence of a positive cosmological constant. However, this can hardly be a truly convincing explanation, as an expanding universe is not expected to have a…
The fact that the energy densities of dark energy and matter are similar currently, known as the coincidence problem, is one of the main unsolved problems of cosmology. We present here a model in which a spatial curvature of the universe…
In this lecture at a school for condensed matter physicists, I begin with basic concepts and tools for investigating phase transitions in quantum field theory. The very different roles of global and gauge symmetries in phase transitions…
Theories of evolving quintessence are constructed that generically lead to deviations from the w = -1 prediction of non-evolving dark energy. The small mass scale that governs evolution, m_\phi \approx 10^{-33} eV, is radiatively stable,…
The cosmological constant is not necessarily small in the early universe. If a scalar field obtains a vacuum expectation value after a phase transition (PT), a possibly large cosmological constant could present before PT. The early…
A quark-gluon phase transition in the Universe is researched after which vacuum (dark) energy has hardened and become cosmological constant. Before this a vacuum component of the Universe was changing by jumps during phase transitions since…
We derive a model of dark energy which evolves with time via the scale factor. The equation of state $\omega=(1-2\alpha)/(1+2\alpha)$ is studied as a function of a parameter $\alpha$ introduced in this model. In addition to the recent…
We investigate the properties of a cosmological scenario which undergoes a gravitational phase transition at late times. In this scenario, the Universe evolves according to general relativity in the standard, hot Big Bang picture until a…