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Michael Maziashvili

Publications and source records attributed to Michael Maziashvili.

At least 37 records · Page 2Linked to original sources

Corrections to the black body radiation due to minimum-length deformed quantum mechanics

Planck spectrum of black body radiation is usually derived by considering of quantized free electromagnetic field at a finite temperature. The minimum-length deformed quantization affects field theory both at the first and second quantization levels. Performing an exact calculation to the first order in deformation parameter, both of the corrections turn out to be of the same order. Nevertheless, the correction at the second quantization level has some qualitative difference, that may be interesting for future study to differentiate between these two sorts of corrections. In itself the correction to the black body radiation seems to be innocuous in light of the big-bang nucleosynthesis whenever the minimum length is less or equal to $10^{-19}$cm.

hep-th↗

Free particle wavefunction in light of the minimum-length deformed quantum mechanics and some of its phenomenological implications

At a fundamental level the notion of particle (quantum) comes from quantum field theory. From this point of view we estimate corrections to the free particle wave function due to minimum-length deformed quantum mechanics to the first order in the deformation parameter. Namely, in the matrix element $<0 |\varPhi(t,\,\mathbf{x}) |\mathbf{p} >$ that in the standard case sets the free particle wave function $\propto \exp(i[\mathbf{p}\mathbf{x} - ε(\mathbf{p}) t])$ there appear three kinds of corrections when the field operator is calculated by using the minimum-length deformed quantum mechanics. Starting from the standard (not modified at the classical level) Lagrangian, after the field quantization we get a modified dispersion relation, and besides that we find that the particle's wave function contains a small fractions of an antiparticle wave function and the backscattered wave. The result leads to interesting implications for black hole physics.

gr-qc↗

Random versus holographic fluctuations of the background metric. II. Note on the dark energies arising due to microstructure of space-time

Over the last few years a certain class of dark-energy models decaying inversely proportional to the square of the horizon distance emerged on the basis either of Heisenberg uncertainty relations or of the uncertainty relation between the four-volume and the cosmological constant. The very nature of these dark energies is understood to be the same, namely it is the energy of background space/metric fluctuations. Putting together these uncertainty relations one finds that the model of random fluctuations of the background metric is favored over the holographic one.

astro-ph.CO↗

Random versus holographic fluctuations of the background metric. I. (Cosmological) running of space-time dimension

A profound quantum-gravitational effect of space-time dimension running with respect to the size of space-time region has been discovered a few years ago through the numerical simulations of lattice quantum gravity in the framework of causal dynamical triangulation [hep-th/0505113] as well as in renormalization group approach to quantum gravity [hep-th/0508202]. Unfortunately, along these approaches the interpretation and the physical meaning of the effective change of dimension at shorter scales is not clear. The aim of this paper is twofold. First, we find that box-counting dimension in face of finite resolution of space-time (generally implied by quantum gravity) shows a simple way how both the qualitative and the quantitative features of this effect can be understood. Second, considering two most interesting cases of random and holographic fluctuations of the background space, we find that it is random fluctuations that gives running dimension resulting in modification of Newton's inverse square law in a perfect agreement with the modification coming from one-loop gravitational radiative corrections.

gr-qc↗

Black hole remnants in RG modified gravity?

The idea of black hole remnants for RG modified Schwarzschild solution constructed in papers [hep-th/0002196; hep-th/0602159] depends essentially on the positiveness of a parameter that enters the running Newton constant. The positiveness of this parameter was established by comparing the large distance expansion of RG modified Schwarzschild solution with the Donoghue's original result about the one-loop correction to the Newtonian potential [gr-qc/9310024; gr-qc/9405057]. But since the appearance of paper [gr-qc/0207118] by Khriplovich and Kirilin it became widely appreciated that the sign of one-loop correction in Donoghue's original result is incorrect. This falsifies the argument for existence of black hole remnants in the framework of modified Schwarzschild solution construction suggested in the above papers. But most importantly the very construction of this modified Schwarzschild solution is challenged by the study of graviton radiative corrections to the Newtonian potential and running Newton constant [hep-th/0211071].

gr-qc↗

Quantum-gravitational running/reduction of space-time dimension

Quantum-gravity renders the space-time dimension to depend on the size of region; it monotonically increases with the size of region and asymptotically approaches four for large distances. This effect was discovered in numerical simulations of lattice quantum gravity in the framework of causal dynamical triangulation [hep-th/0505113] as well as in renormalization group approach to quantum gravity [hep-th/0508202]. However, along these approaches the interpretation and the physical meaning of the effective change of dimension at shorter scales is not clear. Without invoking particular models in this essay we show that, box-counting dimension in face of finite resolution of space-time (generally implied by quantum gravity) shows a simple way how both the qualitative and the quantitative features of this effect can be understood. In this way we derive a simple analytic expression of space-time dimension running, which implies the modification of Newton's inverse square law in a perfect agreement with the modification coming from one-loop gravitational radiative corrections.

hep-th↗

Light incoherence due to quantum-gravitational fluctuations of the background space

Based on the theory of mutual coherence of light from an extended incoherent quasi-monochromatic source (providing a basis of stellar interferometry) we estimate the degree of light incoherence due to quantum-gravitational fluctuations of the background metric. It is shown that the stellar interferometry observational data considered in the literature for a last few years as a manifestation against the Planck scale quantum-gravitational fluctuations of the background metric have no chance for detecting such an effect.

gr-qc↗

Quantum-gravitational corrections to the hydrogen atom and harmonic oscillator

It is shown that the rate of corrections to the hydrogen atom and harmonic oscillator due to profound quantum-gravitational effect of space-time dimension running/reduction coincides well with those obtained by means of the minimum-length deformed quantum mechanics. The rate of corrections are pretty much the same within the accuracy by which we can judge the quantum-gravitational corrections at all. Such a convergence of results makes the concept of space-time dimension running more appreciable. As a remarkable distinction, the energy shift due to dimension reduction has the opposite sign as compared with the correction obtained by means of the minimum-length modified quantum mechanics. Thereby, the sign of total quantum-gravitational correction remains obscure.

hep-th↗

Corrections to the running of gauge couplings due to quantum gravity

Concerning the gravitational corrections to the running of gauge couplings two different results were reported. Some authors claim that gravitational correction at the one-loop level indicates an interesting effect of universal gravitational decreasing of gauge couplings, that is, gravitational correction works universally in the direction of asymptotic freedom no matter how the gauge coupling behaves without gravity, while others reject the presence of gravitational correction at the one-loop level at all. Being these calculations done in the framework of an effective field theory approach to general relativity, we wanted to draw attention to a recently discovered profound quantum-gravitational effect of space-time dimension running that inevitably affects the running of gauge couplings. The running of space-time dimension indicating gradual reduction of dimension as one gets into smaller scales acts on the coupling constants in the direction of asymptotic freedom and therefore in any case manifests the plausibility of this quantum-gravitational effect. Curiously enough, the results are also in perfect quantitative agreement with those of Robinson and Wilczek.

hep-th↗

Cosmological interplay between general relativity and particle physics

We clearly formulate and study further a conjecture of effective field theory interaction with gravity in the cosmological context. The conjecture stems from the fact that the melding of quantum theory and gravity typically indicates the presence of an inherent UV cutoff. Taking note of the physical origin of this UV cutoff, that the background metric fluctuations does not allow QFT to operate with a better precision than the background space resolution, we conjecture that the converse statement might also be true. That is, an effective field theory could not perceive the background space with a better precision than it is allowed by its intrinsic UV scale. Some of the subtleties and cosmological implications of this conjecture are explored.

hep-th↗

Dark energy due to effective quantum field theory

In the cosmological context an effective quantum field theory describing the behavior of visible matter in the universe is characterized with its inherent UV cutoff and also with an IR scale that is set by the cosmological (particle) horizon. This UV - IR relation naturally defines a space-time grid over a horizon scale. Using the approach for determining of dark energy through the space-time uncertainty relation versus such a space-time grid, we estimate the energy density and pressure of a dark energy defined by this UV - IR relation. Such a dark energy shows up to decay linearly with time and exhibits a negative pressure only recently.

hep-ph↗

Comment on "Elementary Kaluza-Klein towers revisited"

Recently the spectrum of KK modes in the framework of one flat extra-dimensional scenario was revisited in the paper Phys. Rev. D74 (2006) 124013, (hep-th/0607246) on the basis of self-adjoint extension of the quantum mechanical operator determining the KK masses. In this Letter we note that the range of allowed boundary conditions on the KK modes is overestimated in above mentioned paper and give all allowed possibilities.

hep-th↗

Space-time uncertainty relation and operational definition of dimension

Operational definition of space-time in light of quantum mechanics and general relativity inevitably indicates an intrinsic imprecision in space-time structure which has to do with space-time dimension as well. The operational dimension of space-time turns out to be a scale dependent quantity slightly smaller than four at distances $\gg l_P$. Close to the Planck length the deviation of space-time dimension from four becomes appreciable. The experimental bounds on the deviation of space-time dimension from four coming from the electron ${\tt g} - 2$ factor, Lamb shift in hydrogen atom and the perihelion shift in the planetary motion are still far from the theoretical predictions.

gr-qc↗

Operational definition of (brane induced) space-time and constraints on the fundamental parameters

First we contemplate the operational definition of space-time in four dimensions in light of basic principles of quantum mechanics and general relativity and consider some of its phenomenological consequences. The quantum gravitational fluctuations of the background metric that comes through the operational definition of space-time are controlled by the Planck scale and are therefore strongly suppressed. Then we extend our analysis to the braneworld setup with low fundamental scale of gravity. It is observed that in this case the quantum gravitational fluctuations on the brane may become unacceptably large. The magnification of fluctuations is not linked directly to the low quantum gravity scale but rather to the higher-dimensional modification of Newton's inverse square law at relatively large distances. For models with compact extra dimensions the shape modulus of extra space can be used as a most natural and safe stabilization mechanism against these fluctuations.

hep-th↗

Cosmological implications of Karolyhazy uncertainty relation

Karolyhazy uncertainty relation, which can be viewed also as a relation between UV and IR scales in the framework of an effective quantum field theory satisfying a black hole entropy bound, strongly favors the existence of dark energy with its observed value. Here we estimate the dynamics of dark energy predicted by the Karolyhazy relation during the cosmological evolution of the universe.

gr-qc↗

Space-time in light of Karolyhazy uncertainty relation

General relativity and quantum mechanics provide a natural explanation for the existence of dark energy with its observed value and predict its dynamics. Dark energy proves to be necessary for the existence of space-time itself and determines the rate of its stability.

gr-qc↗

Do stellar interferometry observations indicate UV modification of gravity?

Recently it was demonstrated that the theoretical predictions for the Planck scale space-time fluctuations derived by the simultaneous consideration of quantum mechanics and general relativity fail by many orders of magnitude against the stellar interferometry observations. We propose the explanation of this puzzle based on the short distance modification of gravity. Roughly speaking the criterion of this modification to fit the astronomical observations is that the gravitational radius of the mass as large as $\sim 10^{26}$kg should not exceed $\sim 10^{-36}$cm. From this point of view we consider the modification of Newtonian inverse square law due to Yukawa type correction and the modification due to quantum gravitational corrections obtained in the framework of nonperturbative RG approach. The latter one does not satisfy the required criterion for modification.

hep-ph↗

Quantum fluctuations of space-time

Using a \emph{gedanken} experiment providing presumably a minimal inaccuracy the uncertainty contributions to the space-time measurement are precisely evaluated for clock and mirror respectively. The resulting expression of minimal uncertainty for the space(time) interval indicates the presence of minimal Planck scale observable length(time). The synthesis of quantum mechanics and general relativity predicts the UV and IR scales for Lorentz invariance violation. The influence of background radiation on the space-time measurement is estimated. Based on the minimal length uncertainty relation which takes into account the wavelength of a quantum used for distance measurement we evaluate the cumulative factor responsible for the magnification of the space-time fluctuation induced phase incoherence of a light propagating over a large distance. We notice that in view of the interferometric observations the quantum fluctuations of space-time in the braneworld model are enormously increased if the fundamental scale is taken much below the Planck one. Present approach to the uncertainty in distance measurement leads to new insight about the bounds of computation. The impact of the space-time fluctuations on the black hole physics is briefly emphasized.

hep-ph↗