arXiv subjects

Rodolfo Gambini

Publications and source records attributed to Rodolfo Gambini.

At least 19 recordsLinked to original sources

arXiv2026

Consistency of the LQG quantization of black holes coupled with scalar matter and a clock

The Dirac quantization of spherically symmetric gravity coupled to a scalar field in Loop Quantum Gravity remains unresolved, mainly because of the difficulty in maintaining a consistent constraint algebra at the quantum level. One possible way to overcome this obstruction is to fix the gauge by coupling the system to a physical clock. However, this approach requires careful control of the consistency of the gauge-fixed theory and factor-ordering ambiguities. Here, we address these issues by analyzing whether the gauge-fixed quantization reproduces the well-known results for the quantization of a black hole in vacuum using the Dirac method. This requires a treatment valid throughout the outer region of the black hole, where the asymptotic approximations considered in previous studies do not hold true.

gr-qc↗

arXiv2025

Quantum panprotopsychism and a consciousness-centered universe

In previous publications, we have argued that a form of panprotopsychism based on quantum states and events offers a solution to the combination problem. This framework explains the emergence of complex phenomenal qualities and conscious subjects. Furthermore, the inherent openness of quantum mechanics allows consciousness and, more generally, phenomenal properties to exert a causal influence. If the view proposed by quantum panprotopsychism is valid, it suggests that we inhabit a consciousness-centered universe. A world whose fundamental nature is phenomenal. This is at odds with the current view about the human condition that was strongly influenced by a science based on classical mechanicism, and led to nihilism and existentialism in late 19th-century Europe, and more recently to the rise of anti-foundationalists perspectives. The centrality of consciousness resulting from the incorporation of a quantum ontology into our worldview leads us to reconsider the nihilistic view and conclude that we live in a world in which a precise physical order leads to people capable of accessing a transcendent phenomenal realm.

physics.hist-ph↗

arXiv2025

Self-consciousness and personal identity in quantum panprotopsychism

In previous papers, we demonstrated that an ontology of quantum mechanics, described in terms of states and events with internal phenomenal aspects (a form of panprotopsychism), is well suited to explain consciousness. We showed that the combination problems of qualities, structures and subjects in panpsychism and panprotopsychism stem from implicit hypotheses based on classical physics regarding supervenience, which are not applicable at the quantum level. Within this view, consciousness arises in entangled quantum systems coupled to the neural network of the brain. In entangled systems, the properties of individual parts disappear, giving rise to an exponential number of emergent properties and states. Here, we analyze self-consciousness as the capacity to view oneself as a subject of experience. The causal openness of quantum systems provides self-conscious beings the ability to make independent choices and decisions, reflecting a sense of self-governance and autonomy. In this context, the issue of personal identity takes a new form free from the problems of the simple view or the reductive approaches.

physics.hist-ph↗

arXiv2024

Quantum panprotopsychism and the structure and subject-summing combination problem

In a previous paper, we have shown that an ontology of quantum mechanics in terms of states and events with internal phenomenal aspects, that is, a form of panprotopsychism, is well suited to explaining the phenomenal aspects of consciousness. We have proved there that the palette and grain combination problems of panpsychism and panprotopsychism arise from implicit hypotheses based on classical physics about supervenience that are inappropriate at the quantum level, where an exponential number of emergent properties and states arise. In this article, we address what is probably the first and most important combination problem of panpsychism: the subject-summing problem originally posed by William James. We begin by identifying the physical counterparts of the subjects of experience within the quantum panprotopsychic approach presented in that article. To achieve this, we turn to the notion of subject of experience inspired by the idea of prehension proposed by Whitehead and show that this notion can be adapted to the quantum ontology of objects and events. Due to the indeterminacy of quantum mechanics and its causal openness, this ontology also seems to be suitable for the analysis of the remaining aspects of the structure combination problem, which shows how the structuration of consciousness could have evolved from primitive animals to humans. The analysis imposes conditions on possible implementations of quantum cognition mechanisms in the brain and suggests new problems and strategies to address them. In particular, with regard to the structuring of experiences in animals with different degrees of evolutionary development.

q-bio.NC↗

arXiv2024

Quantum scalar fields interacting with quantum black hole asymptotic regions

We continue our work on the study of spherically symmetric loop quantum gravity coupled to two spherically symmetric scalar fields, one that acts as a clock. As a consequence of the presence of the latter, we can define a true Hamiltonian for the theory. In previous papers we have studied the theory for large values of the radial coordinate, that is, far away from any black hole or star that may be present. This makes the calculations considerably more tractable. We have shown that in the asymptotic region the theory admits a large family of quantum vacua for quantum matter fields coupled to quantum gravity, as is expected from the well-known results of quantum field theory on classical curved space-time. Here, we study perturbative corrections involving terms that we neglected in our previous work. Using time-dependent perturbation theory, we show that the states that represent different possible vacua are essentially stable. This ensures that one recovers from a totally quantized gravitational theory coupled to matter the standard behavior of a matter quantum field theory plus low probability transitions due to gravity between particles that differ at most by a small amount of energy.

gr-qc↗

arXiv2024

Quantum panprotopsychism and the combination problem

We will argue that a phenomenological analysis of consciousness, similar to that of Husserl, shows that the effects of phenomenal qualities shape our perception of the world. It also shows the way the physical and mathematical sciences operate, allowing us to accurately describe the observed regularities in terms of communicable mathematical laws. The latter say nothing about the intrinsic features of things. They only refer to the observed regularities in their behaviors, providing rigorous descriptions of how the universe works, to which any viable ontology must conform. Classical mechanistic determinism limits everything that can occur to what happens in an instant and leaves no room for novelty or any intrinsic aspect that is not epiphenomenal. The situation changes with quantum probabilistic determinism if one takes seriously the ontology that arises from its axioms of objects, systems in certain states, and the events they produce in other objects. As Bertrand Russell pointed out almost a century ago, an ontology of events, with an internal phenomenal aspect, now known as panprotopsychism, is better suited to explaining the phenomenal aspects of consciousness. The central observation of this paper is that many objections to panpsychism and panprotopsychism, which are usually called the combination problem, arise from implicit hypotheses based on classical physics about supervenience. These are inappropriate at the quantum level, where an exponential number of emergent properties and states arise. The analysis imposes conditions on the possible implementations of quantum cognition mechanisms in the brain.

physics.hist-ph↗

arXiv2023

Quantization of spherically symmetric loop quantum gravity coupled to a scalar field and a clock: the asymptotic limit

We continue our work on the study of spherically symmetric loop quantum gravity coupled to two spherically symmetric scalar fields, one which acts as a clock. As a consequence of the presence of the latter, we can define a true Hamiltonian for the theory. The spherically symmetric context allows to carry out precise detailed calculations. Here we study the theory for regions of large values of the radial coordinate. This allows us to define in detail the vacuum of the theory and study its quantum states, yielding a quantum field theory on a quantum space time that makes contact with the usual treatment on classical space times.

gr-qc↗

arXiv2023

Smooth extensions of black holes in loop quantum gravity

Vacuum spherically symmetric loop quantum gravity in the midi-superspace approximation using inhomogeneous horizon-penetrating slices has been studied for a decade, and it has been noted that the singularity is eliminated. It is replaced by a region of high curvature and potentially large quantum fluctuations. It was recently pointed out that the effective semiclassical metric implies the existence of a shell of effective matter which violates energy conditions in regions where the curvature is largest. Here we propose an alternative way of treating the problem that is free from the shells. The ambiguity in the treatment is related with the existence of new observables in the quantum theory that characterize the area excitations, and how the counterpart of diffeomorphisms in the discrete quantum theory is mapped to the continuum semi-classical picture. The resulting space-time in the high curvature region inside the horizon is approximated by a metric of the type of the Simpson--Visser wormhole and it connects the black hole interior to a white hole in a smooth manner.

gr-qc↗

arXiv2023

Loop quantum gravity of a spherically symmetric scalar field coupled to gravity with a clock

The inclusion of matter fields in spherically symmetric loop quantum gravity has proved problematic at the level of implementing the constraint algebra including the Hamiltonian constraint. Here we consider the system with the introduction of a clock. Using the Abelianizaton technique we introduced in previous papers in the case of gravity coupled to matter, the system can be gauge fixed and rewritten in terms of a restricted set of dynamical variables that satisfy simple Poisson bracket relations. This creates a true Hamiltonian and therefore one bypasses the issue of the constraint algebra. We show how loop quantum gravity techniques may be applied for the vacuum case and show that the Hamiltonian system reproduces previous results for the physical space of states and the observables of a Schwarzchild black hole.

gr-qc↗

arXiv2022

Quantum geometry and black holes

We summarize our work on spherically symmetric midi-superspaces in loop quantum gravity. Our approach is based on using inhomogeneous slicings that may penetrate the horizon in case there is one and on a redefinition of the constraints so the Hamiltonian has an Abelian algebra with itself. We discuss basic and improved quantizations as is done in loop quantum cosmology. We discuss the use of parameterized Dirac observables to define operators associated with kinematical variables in the physical space of states, as a first step to introduce an operator associated with the space-time metric. We analyze the elimination of singularities and how they are replaced by extensions of the space-times. We discuss the charged case and potential observational consequences in quasinormal modes. We also analyze the covariance of the approach. Finally, we comment on other recent approaches of quantum black holes, including mini-superspaces motivated by loop quantum gravity.

gr-qc↗

arXiv2022

The solution to the problem of time in quantum gravity also solves the time of arrival problem in quantum mechanics

We introduced with coauthors some years ago a solution to the problem of time in quantum gravity which consists in formulating the quantum theory in terms of real clocks. It combines Page and Wootters' relational proposal with Rovelli's evolving constants of the motion. Time is associated with an operator and not a classical parameter. We show here that this construction provides a natural solution to the time of arrival problem in quantum mechanics and leads to a well defined time-energy uncertainty relation for the clocks.

gr-qc↗

arXiv2022

Towards a quantum notion of covariance in spherically symmetric loop quantum gravity

The covariance of loop quantum gravity studies of spherically symmetric space-times has recently been questioned. This is a reasonable worry, given that they are formulated in terms of slicing-dependent variables. We show explicitly that the resulting space-times, obtained from Dirac observables of the quantum theory, are covariant in the usual sense of the way -- they preserve the quantum line element -- for any gauge that is stationary (in the exterior, if there is a horizon). The construction depends crucially on the details of the Abelianized quantization considered, the satisfaction of the quantum constraints and the recovery of standard general relativity in the classical limit and suggests that more informal polymerization constructions of possible semi-classical approximations to the theory can indeed have covariance problems. This analysis is based on the understanding of how slicing dependent quantities as the metric arise in a quantum context in terms of parameterized observables. It has implications beyond loop quantum gravity that hold for general approaches to quantum space time theories.

gr-qc↗

arXiv2021

Criticality in the collapse of spherically symmetric massless scalar fields in semi-classical loop quantum gravity

In a recent paper we showed that the collapse to a black hole in one-parameter families of initial data for massless, minimally coupled scalar fields in spherically symmetric semi-classical loop quantum gravity exhibited a universal mass scaling similar to the one in classical general relativity. In particular, no evidence of a mass gap appeared as had been suggested by previous studies. The lack of a mass gap indicated the possible existence of a self-similar critical solution as in general relativity. Here we provide further evidence for its existence. Using an adaptive mesh refinement code, we show that "echoes" arise as a result of the discrete self-similarity in space-time. We also show the existence of "wiggles" in the mass scaling relation, as in the classical theory. The results from the semi-classical theory agree well with those of classical general relativity unless one takes unrealistically large values for the polymerization parameter.

gr-qc↗

arXiv2021

A covariant polymerized scalar field in loop quantum gravity

We propose a new polymerization scheme for scalar fields coupled to gravity. It has the advantage of being a (non-bijective) canonical transformation of the fields and therefore ensures the covariance of the theory. We study it in detail in spherically symmetric situations and compare to other approaches.

gr-qc↗

arXiv2020

Loop quantum black hole extensions within the improved dynamics

We continue our investigation of an improved quantization scheme for spherically symmetric loop quantum gravity. We find that in the region where the black hole singularity appears in the classical theory, the quantum theory contains semi-classical states that approximate general relativity coupled to an effective anisotropic fluid. The singularity is eliminated and the space-time can be continued into a white hole space-time. This is similar to previously considered scenarios based on a loop quantum gravity quantization.

gr-qc↗

arXiv2020

The Montevideo Interpretation: How the inclusion of a Quantum Gravitational Notion of Time Solves the Measurement Problem

We review the Montevideo Interpretation of quantum mechanics, which is based on the use of real clocks to describe physics, using the framework recently introduced by Hoehn, Smith and Lock to treat the problem of time in generally covariant systems. The use of the new formalism makes the whole construction more accessible to readers without familiarity with totally constrained systems. We find that as in the original formulation, a fundamental mechanism of decoherence emerges that allows to supplement ordinary environmental decoherence and avoid its criticisms. Recent results on quantum complexity provide additional support to the type of global protocols used to prove that within ordinary -- unitary -- quantum mechanics no definite event -- an outcome to which a probability can be associated -- occurs. In lieu of this, states that start in a coherent superposition of possible outcomes always remain as a superposition. We show that, if one takes into account fundamental inescapable uncertainties in measuring length and time intervals due to general relativity and quantum mechanics, the previously mentioned global protocols no longer allow to distinguish whether the state is in a superposition or not. One is left with a formulation of quantum mechanics purely defined in quantum mechanical terms without any reference to the classical world and with an intrinsic operational definition of quantum events that does not need external observers.

quant-ph↗

arXiv2020

Fundamental bound for time measurements and minimum uncertainty clocks

We present a simple argument leading to a fundamental minimum uncertainty in the determination of times. It only relies in the uncertainty principle and time dilation in a gravitational field. It implies any attempt to measure times will have a fundamental level of uncertainty. Implications are briefly outlined.

quant-ph↗

arXiv2020

Gravitation in terms of observables 2: the algebra of fundamental observables

In a previous paper, we showed how to use the techniques of the group of loops to formulate the loop approach to gravity proposed by Mandelstam in the 1960's. Those techniques allow to overcome some of the difficulties that had been encountered in the earlier treatment. In this approach, gravity is formulated entirely in terms of Dirac observables without constraints, opening attractive new possibilities for quantization. In this paper we discuss the Poisson algebra of the resulting Dirac observables, associated with the intrinsic components of the Riemann tensor. This provides an explicit realization of the non-local algebra of observables for gravity that several authors have conjectured.

gr-qc↗