scholarly journals Vacuum Condensate Picture of Quantum Gravity

2018 ◽  
Author(s):  
Herbert W. Hamber
Keyword(s):  
Quantum Gravity ◽  
Physical Vacuum ◽  
Vacuum Condensate ◽  
Analytical Treatment ◽  
Long Distance ◽  
Gravitational Vacuum ◽  
Analytic Behavior ◽  
Distance Behavior ◽  
Gravity Perturbation ◽  
New Phase

In quantum gravity perturbation theory in Newton's constant $G$ is known to be badly divergent, and as a result not very useful. Nevertheless, some of the most interesting phenomena in physics are often associated with non-analytic behavior in the coupling constant and the existence of nontrivial quantum condensates. It is therefore possible that pathologies encountered in the case of gravity are more likely the result of inadequate analytical treatment, and not necessarily a reflection of some intrinsic insurmountable problem. The nonperturbative treatment of quantum gravity via the Regge-Wheeler lattice path integral formulation reveals the existence of a new phase involving a nontrivial gravitational vacuum condensate, and a new set of scaling exponents characterizing both the running of $G$ and the long-distance behavior of invariant correlation functions. The appearance of such a gravitational condensate is viewed as analogous to the (equally nonperturbative) gluon and chiral condensates known to describe the physical vacuum of QCD. The resulting quantum theory of gravity is highly constrained, and its physical predictions are found to depend only on one adjustable parameter, a genuinely nonperturbative scale $\xi$ in many ways analogous to the scaling violation parameter $\Lambda_{\bar MS} $ of QCD. Recent results point to significant deviations from classical gravity on distance scales approaching the effective infrared cutoff set by the observed cosmological constant. Such subtle quantum effects are expected to be initially small on current cosmological scales, but could become detectable in future high precision satellite experiments.

scholarly journals Vacuum Condensate Picture of Quantum Gravity

Symmetry ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 87 ◽  
Author(s):  
Herbert Hamber
Keyword(s):  
Quantum Gravity ◽  
Physical Vacuum ◽  
Vacuum Condensate ◽  
Analytical Treatment ◽  
Long Distance ◽  
Gravitational Vacuum ◽  
Analytic Behavior ◽  
Distance Behavior ◽  
Gravity Perturbation ◽  
New Phase

In quantum gravity perturbation theory in Newton’s constant G is known to be badly divergent, and as a result not very useful. Nevertheless, some of the most interesting phenomena in physics are often associated with non-analytic behavior in the coupling constant and the existence of nontrivial quantum condensates. It is therefore possible that pathologies encountered in the case of gravity are more likely the result of inadequate analytical treatment, and not necessarily a reflection of some intrinsic insurmountable problem. The nonperturbative treatment of quantum gravity via the Regge–Wheeler lattice path integral formulation reveals the existence of a new phase involving a nontrivial gravitational vacuum condensate, and a new set of scaling exponents characterizing both the running of G and the long-distance behavior of invariant correlation functions. The appearance of such a gravitational condensate is viewed as analogous to the (equally nonperturbative) gluon and chiral condensates known to describe the physical vacuum of QCD. The resulting quantum theory of gravity is highly constrained, and its physical predictions are found to depend only on one adjustable parameter, a genuinely nonperturbative scale ξ in many ways analogous to the scaling violation parameter Λ M ¯ S of QCD. Recent results point to significant deviations from classical gravity on distance scales approaching the effective infrared cutoff set by the observed cosmological constant. Such subtle quantum effects are expected to be initially small on current cosmological scales, but could become detectable in future high precision satellite experiments.

scholarly journals Gravitational Fluctuations as an Alternative to Inflation III. Numerical Results

Universe ◽  
2020 ◽  
Vol 6 (7) ◽  
pp. 92
Author(s):  
Herbert W. Hamber ◽  
Lu Heng Sunny Yu ◽  
Hasitha E. Pituwala Kankanamge
Keyword(s):  
Observational Data ◽  
Power Spectra ◽  
Scalar Fields ◽  
Observational Cosmology ◽  
Vacuum Condensate ◽  
Analytical Treatment ◽  
Simplifying Assumptions ◽  
Quantum Version ◽  
Gravitational Vacuum ◽  
Limited Precision

Power spectra play an important role in the theory of inflation, and their ability to reproduce current observational data to high accuracy is often considered a triumph of inflation, largely because of a lack of credible alternatives. In previous work we introduced an alternative picture for the cosmological power spectra based on the nonperturbative features of the quantum version of Einstein’s gravity, instead of currently popular inflation models based on scalar fields. The key ingredients in this new picture are the appearance of a nontrivial gravitational vacuum condensate (directly related to the observed cosmological constant), and a calculable renormalization group running of Newton’s G on cosmological scales. More importantly, one notes the absence of any fundamental scalar fields in this approach. Results obtained previously were largely based on a semi-analytical treatment, and thus, while generally transparent in their implementation, often suffered from the limitations of various approximations and simplifying assumptions. In this work, we extend and refine our previous calculations by laying out an updated and extended analysis, which now utilizes a set of suitably modified state-of-the-art numerical programs (ISiTGR, MGCAMB and MGCLASS) developed for observational cosmology. As a result, we are able to remove some of the approximations employed in our previous studies, leading to a number of novel and detailed physical predictions. These should help in potentially distinguishing the vacuum condensate picture of quantum gravity from that of other models such as scalar field inflation. Here, besides the matter power spectrum P m ( k ) , we work out, in detail, predictions for what are referred to as the TT, TE, EE, BB angular spectra, as well as their closely related lensing spectra. However, the current limited precision of observational data today (especially on large angular scales) does not allow us yet to clearly prove or disprove either set of ideas. Nevertheless, by exploring in more details the relationship between gravity and cosmological matter and radiation both analytically and numerically, together with an expected future influx of increasingly accurate observational data, one can hope that the new quantum gravitational picture can be subjected to further stringent tests in the near future.

Shan virtual insurgency and the spectatorship of the nation

2011 ◽  
Vol 42 (1) ◽  
pp. 17-38 ◽  
Author(s):  
Amporn Jirattikorn
Keyword(s):  
Mass Media ◽  
Ethnic Politics ◽  
Long Distance ◽  
New Phase ◽  
Reception Side

The Shan State Army-South (SSA-S) is today one of Burma's largest remaining ethnic opposition armies. This paper investigates ethnic politics of the SSA-S and their strategic use of media. It argues that Shan insurgency today has moved into a new phase characterised by its intense involvement with mass media. The paper examines, on the production side, the Shan insurgency's media products and its networking with the Thai press. On the reception side, it explores how the images of ethnic insurgency are consumed by Shan audiences living in exile, analysing how long-distance Shan nationalism is generated through the spectatorship of these ‘militarised’ images.

scholarly journals THE STRING TENSION IN TWO-DIMENSIONAL GAUGE THEORIES

1999 ◽  
Vol 14 (16) ◽  
pp. 2475-2493 ◽  
Author(s):  
A. ARMONI ◽  
J. SONNENSCHEIN ◽  
Y. FRISHMAN
Keyword(s):  
Finite Temperature ◽  
Gauge Theories ◽  
String Tension ◽  
Temperature Behavior ◽  
Two Dimensional ◽  
Long Distance ◽  
Distance Behavior

We review and elaborate on properties of the string tension in two-dimensional gauge theories. The first model we consider is massive QED in the m≪e limit. We evaluate the leading string tension both in the fermionic and bosonized descriptions. We discuss the next-to-leading corrections in m/e. The next-to-leading terms in the long distance behavior of the quark–antiquark potential, are evaluated in a certain region of external versus dynamical charges. The finite temperature behavior is also determined. In QCD 2 we review the results for the string tension of quarks in cases with dynamical quarks in the fundamental, adjoint, symmetric and antisymmetric representations. The screening nature of SYM 2 is re-derived.

scholarly journals NONLOCAL EFFECTIVE FIELD EQUATIONS FOR QUANTUM COSMOLOGY

2006 ◽  
Vol 21 (09) ◽  
pp. 735-742 ◽  
Author(s):  
H. W. HAMBER ◽  
R. M. WILLIAMS
Keyword(s):  
Quantum Cosmology ◽  
Vacuum Polarization ◽  
Large Time ◽  
Large Time Behavior ◽  
Effective Field ◽  
Adjustable Parameter ◽  
Time Behavior ◽  
Field Equations ◽  
Long Distance ◽  
Gravitational Vacuum

The possibility that the strength of gravitational interactions might slowly increase with distance, is explored by formulating a set of effective field equations, which incorporate the gravitational, vacuum-polarization induced, running of Newton's constant G. The resulting long distance (or large time) behavior depends on only one adjustable parameter ξ, and the implications for the Robertson–Walker universe are calculated, predicting an accelerated power-law expansion at later times t ~ ξ ~ 1/H.

LONG DISTANCE BEHAVIOR OF THE FOUR-DIMENSIONAL NONLINEAR SIGMA MODEL WITH ANOMALY

1993 ◽  
Vol 08 (07) ◽  
pp. 625-634
Author(s):  
BELAL E. BAAQUIE ◽  
S.G. RAJEEV
Keyword(s):  
Fixed Point ◽  
Sigma Model ◽  
Nonlinear Sigma Model ◽  
Stable Fixed Point ◽  
Long Distance ◽  
Group Methods ◽  
Energy Behavior ◽  
Low Energies ◽  
Distance Behavior ◽  
Renormalization Group Methods

We study the low energy behavior of the four-dimensional nonlinear sigma model with anomaly using the 2+∊ expansion and renormalization group methods. It is shown that the theory has a non-trivial ir stable fixed point, in addition to the usual trivial fixed point. If pions happen to exist in the non-trivial phase, their propagator would scale at low energies with anomalous exponents.

scholarly journals TENSORIAL STRUCTURE OF THE LQG GRAVITON PROPAGATOR

2008 ◽  
Vol 23 (08) ◽  
pp. 1209-1213 ◽  
Author(s):  
EMANUELE ALESCI
Keyword(s):  
Asymptotic Behavior ◽  
Quantum Gravity ◽  
Loop Quantum Gravity ◽  
Long Distance ◽  
Graviton Propagator ◽  
Distance Limit

We review the construction of the tensorial structure of the graviton propagator in the context of loop quantum gravity and spinfoam formalism. The main result of this analysis is that applying the same strategy used to compute the diagonal terms, the Barrett-Crane vertex is unable to yield the correct propagator in the long distance limit. The problem is in the intertwiner-independence of the Barrett-Crane vertex. We also review the asymptotic behavior of an alternative vertex that is able to give the correct propagator.

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