Quantum Gravity

Disordered locality as an explanation for the dark energy

by Chanda Prescod-Weinstein

Stellar black holes and the origin of cosmic acceleration

by Chanda Prescod-Weinstein

Macroscopic Objects in Theories with Energy-dependent Speeds of Light

by Chanda Prescod-Weinstein

Does gravity induce wavefunction collapse? An examination of Penrose's argument

by Shan Gao

Draft Version

According to Penrose, the fundamental conflict between the superposition principle of quantum mechanics and the... more According to Penrose, the fundamental conflict between the superposition principle of quantum mechanics and the general covariance principle of general relativity entails the existence of wavefunction collapse, e.g. a quantum superposition of two different space-time geometries will collapse to one of them due to the ill-definedness of the time-translation operator for the superposition. In this paper, we argue that Penrose's conjecture on gravity's role in wavefunction collapse is debatable. First of all, it is still a controversial issue what the exact nature of the conflict is and how to resolve it. Secondly, Penrose's argument by analogy is too weak to establish a necessary connection between wavefunction collapse and the conflict as understood by him. Thirdly, the conflict does not necessarily lead to wavefunction collapse. For the conflict or the problem of ill-definedness for a superposition of different space-time geometries also needs to be solved before the collapse of the superposition finishes, and once the conflict has been resolved, the wavefunction collapse will lose its physical basis relating to the conflict. In addition, we argue that Penrose's suggestions for the collapse time formula and collapse states are also problematic.

A model of wavefunction collapse in discrete space-time

by Shan Gao

International Journal of Theoretical Physics 45, 1965-1979.

We give a new argument supporting a gravitational role in quantum collapse. It is demonstrated that the discreteness... more We give a new argument supporting a gravitational role in quantum collapse. It is demonstrated that the discreteness of space-time, which results from the proper combination of quantum theory and general relativity, may inevitably result in the dynamical collapse of the wave function. Moreover, the minimum size of discrete space-time yields a plausible collapse criterion consistent with experiments. By assuming that the source to collapse the wave function is the inherent random motion of particles described by the wave function, we further propose a concrete model of wavefunction collapse in the discrete space-time. It is shown that the model is consistent with the existing experiments and macroscopic experiences.

Is Gravity an Entropic Force?

by Shan Gao

Entropy special issue “Black Hole Thermodynamics”, Jacob D. Bekenstein (eds). 13, 936-948 (2011).

The remarkable connections between gravity and thermodynamics seem to imply that gravity is not fundamental but... more The remarkable connections between gravity and thermodynamics seem to imply that gravity is not fundamental but emergent, and in particular, as Verlinde suggested, gravity is probably an entropic force. In this paper, we will argue that the idea of gravity as an entropic force is debatable. It is shown that there is no convincing analogy between gravity and entropic force in Verlinde’s example. Neither holographic screen nor test particle satisfies all requirements for the existence of entropic force in a thermodynamics system. Furthermore, we show that the entropy increase of the screen is not caused by its statistical tendency to increase entropy as required by the existence of entropic force, but in fact caused by gravity. Therefore, Verlinde’s argument for the entropic origin of gravity is problematic. In addition, we argue that the existence of a minimum size of spacetime, together with the Heisenberg uncertainty principle in quantum theory, may imply the fundamental existence of gravity as a geometric property of spacetime. This may provide a further support for the conclusion that gravity is not an entropic force.

Measuring Public School Competition from Private Schools: A Gravity-Based Index

by Guangqing Chi

A Gedankenexperiment in Gravitation

by Giovanni Acquaviva

In this paper we consider a thought experiment involving the effect of gravitation on an ideal scale containing a... more In this paper we consider a thought experiment involving the effect of gravitation on an ideal scale containing a photon. If the tidal forces inherent to a gravitational field are neglected, then one is led to scenario which seems to bring about perpetual motion violating the first and second principle of thermodynamics. The tidal effects of gravity must neccessarily be included in order to obtain a consistent physical theory. As a result, Albert Einstein's thought experiments according to which the physical effects of inertia in an accelerated reference frame are equivalent to the effects of gravity in a frame at rest on the surface of a massive body must be reconsidered, since linearly accelerated frames do not produce tidal effects. We argue that the equivalence between inertial effects and gravitation can be restored for rotating frames and in this context a relation with the possible nature of quantum gravity is conjectured.

Horava-Lifshitz gravity: Detailed balance revisited

by Daniele Vernieri

Daniele Vernieri, Thomas P. Sotiriou
Published in Phys. Rev. D 85, 064003 (2012)
e-Print: arXiv:1112.3385v2 [hep-th]

We attempt a critical reconsideration of "detailed balance" as a principle that can be used to restrict the... more We attempt a critical reconsideration of "detailed balance" as a principle that can be used to restrict the proliferation of couplings in Horava-Lifshitz gravity. We re-examine the shortcomings that have been usually associated with it in the literature and we argue that easy remedies can be found for all of them within the framework of detailed balance, and that the most persistent of them are actually related to projectability. We show that, once projectability is abandoned, detailed balance reduces the number of independent couplings by roughly an order of magnitude and imposes only one restriction that constitutes a phenomenological concern: the size of the (bare) cosmological constant is unacceptably large. Remarkably, this restriction (which is present in the projectable version as well) has been so far under-appreciated in the literature. Optimists might prefer to interpret it as a potential blessing in disguise, as it allows one to entertain the idea of a miraculous cancelation between the bare cosmological constant and the (still poorly understood) vacuum energy contribution.

Transition Matrix, Poisson Bracket for gravitational solitons in the dressing formalism

by Panos Kordas

Transition Matrix, Poisson Bracket for gravitational solitons in the dressing formalism

by Panos Kordas

A Bound on Equipartition of Energy v2

by Nicolo' Masi

No presentism in quantum gravity

by Christian Wuthrich

Quantum Gravity and the 3D vs. 4D Controversy

by Christian Wuthrich

Approaching the Planck scale from a generally relativistic point of view: A philosophical appraisal of loop quantum gravity

by Christian Wuthrich

To quantize or not to quantize: fact and folklore in quantum gravity

by Christian Wuthrich

Quantum information paradox: Real or fictitious?

by Abhas Mitra

Information-theoretic metamodel of organization evolution

by Alfred Sepulveda

PhD dissertation

Social organizations are abstractly modeled by holarchies--self-similar connected networks--and intelligent complex... more Social organizations are abstractly modeled by holarchies--self-similar connected networks--and intelligent complex adaptive multiagent systems--large networks of autonomous reasoning agents interacting via scaled processes. However, little is known of how information shapes evolution in such organizations, a gap that can lead to misleading analytics. The research problem addressed in this study was the ineffective manner in which classical model-predict-control methods used in business analytics attempt to define organization evolution. The purpose of the study was to construct an effective metamodel for organization evolution based on a proposed complex adaptive structure--the info-holarchy. Theoretical foundations of this study were holarchies, complex adaptive systems, evolutionary theory, and quantum mechanics, among other recently developed physical and information theories. Research questions addressed how information evolution patterns gleamed from the study's inductive metamodel more aptly explained volatility in organization. In this study, a hybrid grounded theory based on abstract inductive extensions of information theories was utilized as the research methodology. An overarching heuristic metamodel was framed from the theoretical analysis of the properties of these extension theories and applied to business, neural, and computational entities. This metamodel resulted in the synthesis of a metaphor for, and generalization of organization evolution, serving as the recommended and appropriate analytical tool to view business dynamics for future applications. This study may manifest positive social change through a fundamental understanding of complexity in business from general information theories, resulting in more effective management.

Phenomenological Sociography and Time Travel

by Peter Theodoropoulos

Related to questions of Time, structure and aspectual dimensions of relational time. Related theories that I am working on to discuss this are syntactogenerics and syntactogenesis, Syntacto generics and Semanto Generics, Syntactogenesis and Semantogenesis relations, and the nature of time as emminative, immanent and transcendent meaning both virtual and ontological. Please offer your input if you so wish.

What is time? How is time non linear? What are the relational or assemblages of subjective structure, how can we... more What is time? How is time non linear? What are the relational or assemblages of subjective structure, how can we create a taxonomy of types of relational time? By what features does time seem linear, and what is the nature of conditioning, or ritual space that instantiates regularities IN the mind? How is this relation both physical and immaterial? IS there such thing as the immaterial? Can time be said to be Immaterial and materializable? Is time instantiative or phasic, normative and bound to rules or flexible? How do we understand distinctions in subjective and objective time, how can we quantify and compare and contrast variables of each? Is there such thing as a phase shift in which ontological bias may be met with nomological or noumenal objectivity, if so what are the expectations, means of discernment and systems available to explore critique, modify and experiment with time relations? What, finally, are some means to codify and structure simulations of these relations utilizing electromagnetic fields that may interface with the Neural correlates of Consciousness study to explore results? What should our ethical considerations with regards to this sort of study be? How was your day?

Black holes as elementary particles

by Christoph Holzhey

With Frank Wilczek. Nuclear Physics B 380: 447-477, 1992

It is argued that the qualitative features of black holes, regarded as quantum mechanical objects, depend both on the... more It is argued that the qualitative features of black holes, regarded as quantum mechanical objects, depend both on the parameters of the hole and on the microscopic theory in which it is embedded. A thermal description is inadequate for extremal holes. In particular, extreme holes of the charged dilaton family can have zero entropy but non-zero, and even (for $a>1$) formally infinite, temperature. The existence of a tendency to radiate at the extreme, which threatens to overthrow any attempt to identify the entropy as available internal states and also to expose a naked singularity, is at first sight quite disturbing. However by analyzing the perturbations around the extreme holes we show that these holes are protected by mass gaps, or alternatively potential barriers, which remove them from thermal contact with the external world. We suggest that the behavior of these extreme dilaton black holes, which from the point of view of traditional black hole theory seems quite bizarre, can reasonably be interpreted as the holes doing their best to behave like normal elementary particles. The $a<1$ holes behave qualitatively as extended objects.