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Michael Maziashvili

Publications and source records attributed to Michael Maziashvili.

At least 19 recordsLinked to original sources
arXiv2026

Field theory vacuum and entropic dark energy models

While in the standard quantization the energy spectrum of oscillator does not depend on its mass - for Planck length deformed quantization the energy spectrum becomes mass dependent. That means that the field oscillator masses will source a gravitational field through the Nullpunktsenergie as long as we follow this scheme of quantization. Admitting these masses are tangible, their gravitational effect will manifest itself even within the framework of standard field theory. We shall consider the possible gravitational implications based on this approach. If the mass scale for field oscillators is set by the inverse size of the box containing the field and three-momentum cutoff dictated by the black hole energy bound is exploited, one finds that the number of Fourier modes saturates the black hole entropy bound. Following certain "holographic" reasoning, one can derive various kinds of dark energy models that maybe interesting for further study.

gr-qc↗
arXiv2023

Saving CNB assisted EDE model at the expense of quantum corrections?

As it is suggested in \cite{Sakstein:2019fmf, CarrilloGonzalez:2020oac}, one can dynamically introduce the coincidence time-scale for EDE in the framework of a particular mass-varying-neutrino-model as a time at which neutrinos constituting the cosmic neutrino background enter the non-relativistic regime. The model does not predict, however, the right amount of EDE density because of smallness of neutrino masses. One may hope to adjust the parameters in such a way as to ensure that the two-loop contributions are kept small while at the same time the effective mass for scalar field that enters the expression of zero-point-energy (for the field trapped in the minimum of effective potential) is sufficient for explaining the needed amount of EDE. Unfortunately, the answer is not in the affirmative.

astro-ph.CO↗
arXiv2023

Avoiding parameter fine-tuning in mass varying neutrino models of DE?

Coupled models of quintessence are usually introduced for avoiding or mitigating the parameter fine-tuning problem. At the same time, the coupled models should avoid the fine-tuning problem related to the initial conditions as quintessence models do. One more attractive feature of coupled models might be the explanation of the timescale at which the coincidence of DE and matter energy densities occur and the understanding of reason why after this the DE takes over. And finally, all these nice features should be unaffected by the quantum corrections of the potential. Having in mind these remarks, we shall focus our discussion on mass varying neutrino model of DE with inverse power-law potential to see how naturally does it work.

astro-ph.CO↗
arXiv2021

Inflaton-driven early dark energy

By arranging the control parameters, we examine whether the mass varying neutrino model PRD 103, 063540 (2021), enabling one to unify inflation with the present dark energy, can be used for producing an early dark energy. The model works in the following way. At early stages of the Big-Bang, the inflaton trapped in the minimum at $ϕ= 0$ gets uplifted due to interaction with neutrinos and starts to roll down to one of the degenerate minima of the effective potential and after a while gets anchored at this minimum, which in turn evolves in time very slowly. Correspondingly, the early dark energy taking place as a result of this dynamical symmetry breaking also varies in time very slowly. Shortly before the recombination epoch, however, the symmetry is restored and early dark energy disappears. A typical problem of the mass varying neutrino models is that they can hardly provide the needed amount of early dark energy at the tree-level because of smallness of neutrino masses. Nevertheless, the quantum fluctuations of $ϕ$ can do the job in providing sufficient early dark energy under assumption that inflationary energy scale is of the order of $1$\,TeV. Radiative as well as thermal corrections coming from the neutrino sector do not affect the model significantly. As for the gravity induced corrections to the effective potential - they can be safely ignored.

astro-ph.CO↗
arXiv2021

Non-local imprints of gravity on quantum theory

During the last two decades or so much effort has been devoted to the discussion of quantum mechanics (QM) that in some way incorporates the notion of a minimum length. This upsurge of research has been prompted by the modified uncertainty relation brought about in the framework of string theory. In general, the implementation of minimum length in QM can be done either by modification of position and momentum operators or by restriction of their domains. In the former case we have the so called soccer-ball problem when the naive classical limit appears to be drastically different from the usual one. Starting with the latter possibility, an alternative approach was suggested in the form of a band-limited QM. However, applying momentum cutoff to the wave-function, one faces the problem of incompatibility with the Schrödinger equation. One can overcome this problem in a natural fashion by appropriately modifying Schrödinger equation. But incompatibility takes place for boundary conditions as well. Such wave-function cannot have any more a finite support in the coordinate space as it simply follows from the Paley-Wiener theorem. Treating, for instance, the simplest quantum-mechanical problem of a particle in an infinite potential well, one can no longer impose box boundary conditions. In such cases, further modification of the theory is in order. We propose a non-local modification of QM, which has close ties to the band-limited QM, but does not require a hard momentum cutoff. In the framework of this model, one can easily work out the corrections to various processes and discuss further the semi-classical limit of the theory.

quant-ph↗
arXiv2021

A new take on the inflationary quintessence

The quintessence field coupled to the cosmic neutrino background (CNB) has been widely discussed as an alternative mechanism to address the coincidence problem. As it is well known, it is possible to extend such models to obtain quintessential inflation, that is, to incorporate inflationary stage as well. Taking an alternative route, one can start from the well established inflationary models and obtain successful quintessence models at the expense of coupling with the CNB. To Follow this route, we use a slightly reformulated model addressed in PRD95, 123521 (2017). This particular model assumes $\mathcal{Z}_2$ symmetry for both scalar field potential and coupling term, which then breaks down in course of the cosmological evolution. For our discussion, however, the $\mathcal{Z}_2$ symmetry of the potential is not mandatory the model to work. The conventional mechanism of particle production by the oscillating inflaton field (and their subsequent thermalization) remains operative. It is plain to see that the proposed construction can be easily applied for many successful models of inflation to incorporate dark energy at the expense of coupling with the CNB. We address the issue of neutrino nuggets from the quantum field theory point of view. Namely, these nuggets are considered as bound states caused basically by the Yukawa force, which arises in the framework of linear perturbation theory due to exchange of virtual quanta of quintessence field between the neutrinos.

astro-ph.CO↗
arXiv2020

Mean lifetime of a false vacuum in terms of the Krylov-Fock non-escape probability

The Krylov-Fock expression of non-decay (or survival) probability, which allows to evaluate the deviations from the exponential decay law (nowadays well established experimentally), is more informative as it readily provides the distribution function for the lifetime as a random quantity. Guided by the well established formalism for describing nuclear alpha decay, we use this distribution function to figure out the mean value of lifetime and its fluctuation rate. This theoretical framework is of considerable interest inasmuch as it allows an experimental verification. Next, we apply the Krylov-Fock approach to the decay of a metastable state at a finite temperature in the framework of thermo-field dynamics. In contrast to the existing formalism, this approach shows the interference effect between the tunnelings from different metastable states as well as between the tunneling and the barrier hopping. This effect looks quite natural in the framework of consistent quantum mechanical description as a manifestation of the "double-slit experiment". In the end we discuss the field theory applications of the results obtained.

hep-th↗
arXiv2019

Salecker-Wigner-Karolyhazy Gedankenexperiment in light of the self-gravity

In Gedankenexperiment mentioned in the title, the imprecision in space-time measurement is related to the spreading of clock's wave-function with the passage of time required for the measurement. Special relativity puts a bound on the measurement time, it cannot be reduced arbitrarily as the signal used for the measurement cannot propagate with speed greater than that of light. In view of this reasoning, one is led to conclude that the clock should be heavy enough to slow down its wave-function from spreading with time. However, the general relativity puts an upper bound on clock's mass, since its size must remain greater then the Schwarzschild radius associated to it. This way one reaches a limit in length measurement. However, as is discussed below, an additional insight into the question comes by taking into account self-gravitational effects. As a result, the uncertainty in length measurement is reduced to the Planck length.

gr-qc↗
arXiv2018

IR/UV corrections to the Casimir force

Hard momentum cutoff is used for estimating IR/UV corrections to the Casimir force. In contrast to the power-law corrections arising from the IR cutoff, one will find the UV cutoff-dependent corrections to be exponentially suppressed. As a consequence of this fact, there is no chance to detect the corrections due to UV cutoff arising for instance from the "minimum-length" scenarios even if fundamental quantum-gravity scale is taken around $\sim$ TeV (as is the case, for example, in various models with extra dimensions).

quant-ph↗
arXiv2016

Light incoherence due to background space fluctuations

Working by analogy, we use the description of light fluctuations due to random collisions of the radiating atoms to figure out why the reduction of the coherence for light propagating a cosmological distance in the fluctuating background space is negligibly small to be observed by the stellar interferometry.

gr-qc↗
arXiv2016

Macroscopic detection of deformed QM by the harmonic oscillator

Based on the nonperturbative analysis, we show that the classical motion of harmonic oscillator derived from the deformed QM is manifestly in contradiction with observations. For this reason, we take an alternate way for estimating the effect and discuss its possible observational manifestations in macrophysics.

hep-ph↗
arXiv2015

Black hole remnants due to Planck-length deformed QFT

It was argued in a number of papers that the gravitational potential calculated by using the modified QFT that follows from the Planck-length deformed uncertainty relation implies the existence of black-hole remnants of the order of the Planck-mass. Usually this sort of QFTs are endowed with two specific features, the modified dispersion relation, which is universal, and the concept of minimum length, which, however, is not universal. While the emergence of the minimum-length most readily leads to the idea of the black hole remnants, here we examine the behaviour of the potential that follows from the Planck-length deformed QFT in absence of the minimum length and show that it might also lead to the formation of the Planck mass black holes in some particular cases. The calculations are made for higher-dimensional case as well. Such black hole remnants might be considered as a possible candidates for the dark-matter.

gr-qc↗
arXiv2015

Extra-dimensional generalization of minimum-length deformed QM/QFT and some of its phenomenological consequences

In contrast to the 3D case, different approaches for deriving the gravitational corrections to the Heisenberg uncertainty relation do not lead to the unique result whereas additional spatial dimensions are present in the theory. We suggest to take logarithmic corrections to the black hole entropy, which has recently been proved both in string theory and loop quantum gravity to persist in presence of additional spatial dimensions, as a point of entry for identifying the modified Heisenberg-Weyl algebra. We then use a particular Hilbert space representation for such a quantum mechanics to construct the correspondingly modified field theory and address some phenomenological issues following from it. Some subtleties arising at the second quantization level are clearly pointed out. Solving the field operator to the first order in deformation parameter and defining the modified wave function for a free particle, we discuss the possible phenomenological implications for the black hole evaporation. Putting aside modifications arising at the second quantization level, we address the corrections to the gravitational potential due to modified propagator (back reaction on gravity) and see that correspondingly modified Schwarzschild-Tangherlini space-time shows up the disappearance of the horizon and vanishing of surface gravity when black hole mass approaches the quantum gravity scale. This result points out to the existence of zero-temperature black hole remnants.

hep-th↗
arXiv2014

Minimum-length deformed QM/QFT, issues and problems

Using a particular Hilbert space representation of minimum-length deformed quantum mechanics, we show that the resolution of the wave-function singularities for strongly attractive potentials, as well as cosmological singularity in the framework of a minisuperspace approximation, is uniquely tied to the fact that this sort of quantum mechanics implies the reduced Hilbert space of state-vectors consisting of the functions nonlocalizable beneath the Planck length. (Corrections to the Hamiltonian do not provide such an universal mechanism for avoiding singularities.) Following this discussion, as a next step we take a critical view of the meaning of wave-function in such a quantum theory. For this reason we focus on the construction of current vector and the subsequent continuity equation. Some issues gained in the framework of this discussion are then considered in the context of field theory. Finally, we discuss the classical limit of the minimum-length deformed quantum mechanics and its dramatic consequences.

hep-th↗
arXiv2013

Minimum length, extra dimensions, modified gravity and black hole remnants

We construct a Hilbert space representation of minimum-length deformed uncertainty relation in presence of extra dimensions. Following this construction, we study corrections to the gravitational potential (back reaction on gravity) with the use of correspondingly modified propagator in presence of two (spatial) extra dimensions. Interestingly enough, for $r \rightarrow 0$ the gravitational force approaches zero and the horizon for modified Schwarzschild-Tangherlini space-time disappears when the mass approaches quantum-gravity energy scale. This result points out to the existence of zero-temperature black hole remnants in ADD brane-world model.

hep-th↗
arXiv2012

Implications of minimum-length deformed quantum mechanics for QFT/QG

After picking out what may seem more realistic minimal gravitational deformation of quantum mechanics, we study its back reaction on gravity. The large distance behaviour of Newtonian potential coincides with the result obtained by using of effective field theory approach to general relativity (the correction proves to be of repulsive nature). The short distance corrections result in Planck mass black hole remnants with zero temperature. The deformation of position-momentum uncertainty relations leads to the superluminal motion that can be avoided by making similar deformation of time-energy uncertainty relation. Such deformation also avoids UV divergences in QFT.

gr-qc↗
arXiv2012

Minimum-length deformed quantization of a free field on de Sitter background and corrections to the inflaton perturbations

The effect of string and quantum gravity inspired minimum-length deformed quantization on a free, massless scalar field is studied on de Sitter background at the level of second quantization. Analytic solution of a field operator is obtained to the first order in deformation parameter. Using this solution we then estimate the two point and four point correlation functions (with respect to the Bunch-Davies vacuum). The field operator shows up a non-linear dependence on creation and annihilation operators, therefore the perturbation spectrum proves to be non-Gaussian. The correction to the power spectrum is of the same order as obtained previously in a similar study that incorporates the minimum-length deformed momentum operator into the first quantization picture and then proceeds in the standard way for second quantization. The non-Gaussianity comes at the level of four point correlation function; its magnitude appears to be suppressed by the factor $\sim\exp(-6N)$, where $N$ is the number of e-foldings.

gr-qc↗