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In this study, we discuss an analytical solution for a set of the Klein–Gordon (KG) oscillators’ energies through a correlation between the frequency of the KG-oscillators and the traversable wormhole (TWH) throat radius. Under such restricted parametric correlation (hence the notion of conditionally exact solvability is unavoidable in the process), we report the effects of throat radius, rainbow parameter, disclination parameter and oscillator frequency on the spectroscopic structure of a vast number of (n,m)-states (the radial and magnetic quantum numbers, respectively). In the process, we only use two loop quantum gravity motivated rainbow functions pairs. Only rainbow functions clearly and reliably fully adhere to the rainbow gravity model and secure Planck energy Ep as the maximum possible energy for particles and anti-particles alike. Near the asymptotically flat upper and lower universes connected by the TWH, i.e. for the throat radius r0 ≫ 1, the energies tend to cluster around the rest mass energies, i.e. |E±|∼ m0. Whereas, for r0 ≪ 1, the energies tend to approach |E±|≤ EP. [ABSTRACT FROM AUTHOR]

Bell-network states are a class of entangled states of the geometry that satisfy an area-law for the entanglement entropy in a limit of large spins and are automorphism-invariant, for arbitrary graphs. We present a comprehensive analysis of the effective geometry of Bell-network states on a dipole graph. Our main goal is to provide a detailed characterization of the quantum geometry of a class of diffeomorphism-invariant, area-law states representing homogeneous and isotropic configurations in loop quantum gravity, which may be explored as boundary states for the dynamics of the theory. We found that the average geometry at each node in the dipole graph does not match that of a flat tetrahedron. Instead, the expected values of the geometric observables satisfy relations that are characteristic of spherical tetrahedra. The mean geometry is accompanied by fluctuations with considerable relative dispersion for the dihedral angle, and perfectly correlated for the two nodes. [ABSTRACT FROM AUTHOR]

The present electrostatic accelerometers (EA) drift at low frequencies. To address this problem, integrating a cold atom interferometry (CAI) accelerometer could be beneficial, as it offers the potential for superior long-term stability. The CAI-based accelerometers (CAI ACC) are accurate and stable, but they have some issues with long dead times and a relatively small dynamic range. A way to address these problems is to combine a CAI ACC with an EA in a hybrid configuration. Using CAI ACC in an upcoming satellite gradiometry mission can give stable and accurate measurements of the static Earth's gravity field. Three scenarios have been considered in this study: first, a realistic scenario involving current-generation and realistic hybrid accelerometers; second, a semi-realistic scenario with the same accelerometers and an accurate gyroscope; and third, using highly accurate hybrid/CAI accelerometers with an optimistic gyroscope. One significant aspect was on detecting temporal gravity changes, which cannot compare to the effectiveness of the low-low satellite-to-satellite tracking (LLSST) principle. But, quantum gradiometers can significantly enhance solutions for the static gravity field, provided one has accurate observations of the satellite orientation available. [ABSTRACT FROM AUTHOR]

Bekenstein bound provides a universal bound on entropy for a black hole that is independent of mass. The universal nature of Entropy and area product of multi-horizon black holes ensure the existence of dual in 2D CFT. So, studying various sums and product relations of thermodynamic quantities, such as entropy. area, Komar energy, etc., for black holes having multiple horizons, has become a trend in quantum gravity. In this paper, we studied the thermodynamic relations of the Ernst black hole. First, we calculated temperature, area, entropy and Komar energies. Then, we derived their sums and products and found that they are not universal except for area. Lastly, we studied thermodynamics with the Generalized Uncertainty Principle (GUP) to verify the effect of the dispersion of space-time on the stability and other behavior of the Ernst black hole. [ABSTRACT FROM AUTHOR]

Before we ask what the quantum gravity theory is, there is a legitimate quest to formulate a robust quantum field theory in curved spacetime (QFTCS). Several conceptual problems, especially unitarity loss (pure states evolving into mixed states), have raised concerns over several decades. In this paper, acknowledging the fact that time is a parameter in quantum theory, which is different from its status in the context of General Relativity (GR), we start with a "quantum first approach" and propose a new formulation for QFTCS based on the discrete spacetime transformations which offer a way to achieve unitarity. We rewrite the QFT in Minkowski spacetime with a direct-sum Fock space structure based on the discrete spacetime transformations and geometric superselection rules. Applying this framework to QFTCS, in the context of de Sitter (dS) spacetime, we elucidate how this approach to quantization complies with unitarity and the observer complementarity principle. We then comment on understanding the scattering of states in de Sitter spacetime. Furthermore, we discuss briefly the implications of our QFTCS approach to future research in quantum gravity. [ABSTRACT FROM AUTHOR]

Genus one amplitude for topological strings on Calabi–Yau 3-folds can be computed using mirror symmetry: The partition function at genus one gets mapped to a holomorphic version of Ray–Singer torsion on the mirror Calabi–Yau. On the other hand it can be shown by a physical argument that this gives a curvature squared correction term to the gravitational action. This in paticular leads to an effective quantum gravity cutoff known as the species scale, which varies over moduli space of Calabi–Yau manifolds. This resolves some of the puzzles associated to the entropy of small black holes when there are a large number of light species of particles. Thus Ray–Singer torsion, via its connection to topological strings at genus one, provides a measure of light degrees of freedom of four dimensional \mathcal {N}=2 supergravity theories. [ABSTRACT FROM AUTHOR]

A relation between dark energy and the scale of new physics in weakly coupled string theory is motivated. This mixing between infrared and ultraviolet physics leads to a unique corner for real‐world phenomenology: barring fine‐tunings, the authors are naturally led to the “dark dimension” scenario, a single mesoscopic extra dimension of micron size with the standard model localized on D‐branes. Our explicit top‐down worldsheet derivation establishes it on a more solid grounding. Allowing some fine‐tuning, such that the vacuum energy only arise at higher orders in string perturbation theory, the “little string theory” scenario with a very weakly coupled string is an alternative possibility. In this case, the string scale lies at the edge of detectability of particle accelerators. [ABSTRACT FROM AUTHOR]

This review is a contribution to a book dedicated to the memory of Michael E. Fisher. The first example of a quantum many body system not expected to have any quasiparticle excitations was the Wilson-Fisher conformal field theory. The absence of quasiparticles can be established in the compressible, metallic state of the Sachdev-Ye-Kitaev model of fermions with random interactions. The solvability of the latter model has enabled numerous computations of the non-quasiparticle dynamics of chaotic many-body states, such as those expected to describe quantum black holes. We review thermodynamic properties of the SYK model, and describe how they have led to an understanding of the universal structure of the low energy density of states of charged black holes without low energy supersymmetry. [ABSTRACT FROM AUTHOR]

The experimental verification of the Newton law of gravity at small scales has been a longstanding challenge. Recently, torsion balance experiments have successfully measured gravitational force at the millimeter scale. However, testing gravity force on quantum mechanical wave function at small scales remains difficult. In this paper, we propose a novel experiment that utilizes the Josephson effect to detect the different evolution of quantum phase induced from the potential difference caused by gravity. We demonstrate that this experiment can test gravity quantum mechanically at the millimeter scale, and also has a potential to investigate the parity invariance of gravity at small scales. [ABSTRACT FROM AUTHOR]

General relativity and quantum mechanics are not only fundamentally different theories giving explanations of how nature works but also genuinely incompatible descriptions of reality. The violation of the principles of relativity and equivalence, at quantum scales, belongs to the main conceptual difficulties of reconciling principles of quantum mechanics with general relativity so that their scales of applicability are entirely distinct. When generalized noncommutative Heisenberg algebra accommodating impacts of finite gravitational fields as specified by quantum loop gravity, doubly special relativity, and string theory, for instance, is thoughtfully applied to the eight-dimensional Finsler manifold. In the natural generalization of the pseudo-Riemannian manifold, in which the quadratic restriction on the length measure is relaxed, we have been able to define quantum-induced revisiting fundamental tensor in relativistic regime and thereby extending its applicability to quantum scales. By constructing the affine connections on a four-dimensional pseudo-Riemannian manifold, we have determined the quantum-induced revisiting Riemann curvature tensor and its contractions, the Ricci curvature tensor, and scalar in relativistic regime. Consequently, we have been able to construct the Einstein tensor, in which besides quantization additional geometric structures and curvatures are emerged. As in Einstein's classical theory of general relativity, we have proved that the covariant derivative of the modified Einstein tensor vanishes, as well. We conclude that the quantum-induced corrections establish quantum properties to the space–time coordinates and momenta. Accordingly, the space–time curvature endows additional curvature and geometrical structure as well as discretization which likely enable sensical predictions of Einstein's general relativity, at the quantum scale. [ABSTRACT FROM AUTHOR]

Schramm–Loewner evolution (SLE) curves describe the scaling limit of interfaces from many 2D lattice models. Heuristically speaking, the SLE partition function is the continuum counterpart of the partition function of the corresponding discrete model. It is well known that conformally welding of Liouville quantum gravity (LQG) surfaces gives SLE curves as the interfaces. In this paper, we demonstrate in several settings how the SLE partition function arises from conformal welding of LQG surfaces. The common theme is that we conformally weld a collection of canonical LQG surfaces which produces a topological configuration with a random conformal structure. Conditioning on the conformal modulus, the surface after welding is described by Liouville conformal field theory, and the density of the random modulus contains the SLE partition function for the interfaces as a multiplicative factor. The settings we treat includes the multiple SLE for |$\kappa \in (0,4)$|⁠ , the flow lines of imaginary geometry on the disk with boundary marked points, and the boundary Green function. These results demonstrate an alternative approach to construct and study the SLE partition function, which complements the traditional method based on stochastic calculus and differential equation. [ABSTRACT FROM AUTHOR]

We present a first analysis of a nonperturbative approach to quantum gravity based on a representation of quantum field theory in terms of stochastic processes. The stochastic description accommodates a physical Lorentz-invariant ultraviolet regulator that provides a novel description of physics at ultra-short distances. In a scalar toy model, we demonstrate the evolution of a generic initial field configuration toward an equilibrium in which the composite spacetime metric fluctuates about a flat spacetime. As a diffeomorphism-invariant theory with locally Lorentz-invariant regulator, fluctuations about the vacuum are expected to give rise to an emergent gravitational interaction consistent with Einstein gravity at long distances. We uncover a formal similarity between regularization by stochastic discreteness and point-splitting regularization in the corresponding quantum field theory. We comment on the signature of the emergent spacetime, possible consequences for the early universe, and the potential for observational and experimental tests of the stochastic origin of quantum field theory and gravitation. [ABSTRACT FROM AUTHOR]

The article in the International Journal of Modern Physics A highlights the significant contributions of Lars Brink to string theory and supersymmetry. Brink's work in the 1970s, particularly with Holger Nielsen and David Olive, advanced the understanding of string theory, one-loop amplitudes, and supersymmetric Yang-Mills theories. His collaborations led to groundbreaking discoveries in theoretical physics, including the development of N=4 super Yang-Mills theory. Brink's research has had a lasting impact on the field and continues to influence theoretical physics today. [Extracted from the article]

Hawking's seminal work on black hole radiation highlights a critical issue in our understanding of quantum field theory in curved spacetime (QFTCS), specifically the problem of unitarity loss (where pure states evolve into mixed states). In this paper, we examine a recent proposal for a direct-sum QFTCS, which maintains unitarity through a novel quantization method that employs geometric superselection rules based on discrete spacetime transformations. This approach describes a quantum state in terms of components that evolve within geometric superselection sectors of the complete Hilbert space, adhering to the discrete symmetries of a Schwarzschild black hole. Consequently, it represents a maximally entangled pure state as a direct-sum of two components in the interior and exterior regions of the black hole, thereby preserving the unitarity of Hawking radiation by keeping it in the form of pure states. [ABSTRACT FROM AUTHOR]

We investigate the perturbation of the scalar field as well as the electromagnetic field over a sort of regular black holes which are characterized by the sub-Planckian curvature and the Minkowskian core. Specifically, we compute the quasinormal modes (QNMs) by employing the pseudo-spectral method. The outburst of overtones is manifestly observed in the QNMs of these regular black holes, which can be attributed to the deviation of the Schwarzschild black hole by quantum effects of gravity. Furthermore, the QNMs under the perturbation of electromagnetic field exhibit smaller real and imaginary parts than those under scalar field perturbation. By comparing the QNMs of the regular black hole featured by Minkowskian core with those of Bardeen black hole featured by de Sitter core, we find they may be an effective tool to distinguish these BHs. [ABSTRACT FROM AUTHOR]

We investigate thermodynamics of apparent horizon in the f(Q) universe with trivial and nontrivial connections. We first explore the perspectives of the first law, generalized second law and P–V phase transition with trivial connection. We show that the lowest-order correction of entropy has the same form as that in loop quantum gravity, and the critical exponents of the phase transition caused by the lowest-order correction are consistent with those in mean field theory. We then examine the thermodynamic implication of nontrivial connections. We find that nontrivial connections in the f(Q) universe imply non-equilibrium states from the perspective of thermodynamics. [ABSTRACT FROM AUTHOR]

We investigate a compelling model of a rotating black hole that is deformed by the effects of loop quantum gravity (LQG). We present a simplified metric and explore two distinct geometries: one in which the masses of the black hole and white hole are equal, and another in which they differ. Our analysis yields the radius of the innermost stable circular orbits (ISCO), as well as the energy and angular momentum of a particle within this framework. Additionally, we find the frequency of the first-order resonance separately. We constrain the model by the quasi-periodic oscillations (QPO) of the X-ray binary GRO J1655-40. We show that λ = 0. 15 - 0.14 + 0.23 at 1 σ confidence level for equal mass black hole and white hole geometry. For the other geometry we get λ = 0. 11 - 0.07 + 0.07 at 1 σ confidence level. We encounter a degeneracy in the parameter space that hinders our ability to constrain λ with greater precision. [ABSTRACT FROM AUTHOR]

We propose a consistent framework with the U(1) Peccei–Quinn (PQ) symmetry for obtaining the initial condition for axion kinetic misalignment from inflation. We introduce a PQ complex scalar field and an extra Higgs doublet, which are conformally coupled to gravity, and three right-handed neutrinos for the seesaw mechanism. In the DFSZ type scenarios for the axion, we obtain the PQ anomalies from the Standard Model quarks carrying nonzero PQ charges in some of two Higgs doublet models, solving the strong CP problem by the QCD potential for the axion. Assuming that the PQ symmetry is explicitly violated in the scalar potential by quantum gravity effects, we show that a sufficiently large initial axion velocity can be obtained before the QCD phase transition while avoiding the axion quality problem. As inflation is driven by the radial distance from the origin in the space of scalar fields close to the pole of the kinetic terms in the Einstein frame, we obtain successful inflationary predictions and set the initial axion velocity at the end of inflation. Focusing on the pure PQ inflation with a small running quartic coupling for the PQ field, we discuss the post-inflationary dynamics for the inflaton and the axion. As a result, we show that a sufficiently high reheating temperature can be obtained dominantly from the Higgs-portal couplings to the PQ field, while being consistent with axion kinetic misalignment, the stability for the Higgs fields during inflation and the non-restoration of the PQ symmetry after reheating. [ABSTRACT FROM AUTHOR]

Interest on the possible future scenarios the universe could have has grew substantially with breakthroughs on late-time acceleration. Holographic dark energy (HDE) presents a very interesting approach towards addressing late-time acceleration, presenting an intriguing interface of ideas from quantum gravity and cosmology. In this work we present an extensive discussion of possible late-time scenarios, focusing on rips and similar events, in a universe with holographic dark energy. We discuss these events in the realm of the generalized Nojiri–Odintsov cutoff and also for the more primitive holographic cutoffs like Hubble, particle and event horizon cutoffs. We also discuss the validity of the generalized second law of thermodynamics and various energy conditions in these regimes. Our work points towards the idea that it is not possible to have alternatives of the big rip consistently in the simpler HDE cutoffs, and shows the flexibility of the generalized HDE cutoff as well. [ABSTRACT FROM AUTHOR]

We present the Quantum Memory Matrix (QMM) hypothesis, which addresses the longstanding Black Hole Information Paradox rooted in the apparent conflict between Quantum Mechanics (QM) and General Relativity (GR). This paradox raises the question of how information is preserved during black hole formation and evaporation, given that Hawking radiation appears to result in information loss, challenging unitarity in quantum mechanics. The QMM hypothesis proposes that space–time itself acts as a dynamic quantum information reservoir, with quantum imprints encoding information about quantum states and interactions directly into the fabric of space–time at the Planck scale. By defining a quantized model of space–time and mechanisms for information encoding and retrieval, QMM aims to conserve information in a manner consistent with unitarity during black hole processes. We develop a mathematical framework that includes space–time quantization, definitions of quantum imprints, and interactions that modify quantum state evolution within this structure. Explicit expressions for the interaction Hamiltonians are provided, demonstrating unitarity preservation in the combined system of quantum fields and the QMM. This hypothesis is compared with existing theories, including the holographic principle, black hole complementarity, and loop quantum gravity, noting its distinctions and examining its limitations. Finally, we discuss observable implications of QMM, suggesting pathways for experimental evaluation, such as potential deviations from thermality in Hawking radiation and their effects on gravitational wave signals. The QMM hypothesis aims to provide a pathway towards resolving the Black Hole Information Paradox while contributing to broader discussions in quantum gravity and cosmology. [ABSTRACT FROM AUTHOR]

In this letter, we highlight the structure and main properties of an abstract approach to quantum cosmology and gravity, dubbed S U (∞) -QGR. Beginning from the concept of the Universe as an isolated quantum system, the main axiom of the model is the existence of an infinite number of mutually commuting observables. Consequently, the Hilbert space of the Universe represents S U (∞) symmetry. This Universe as a whole is static and topological. Nonetheless, quantum fluctuations induce local clustering in its quantum state and divide it into approximately isolated subsystems representing G × S U (∞) , where G is a generic finite-rank internalsymmetry. Due to the global S U (∞) each subsystem is entangled to the rest of the Universe. In addition to parameters characterizing the representation of G, quantum states of subsystems depend on four continuous parameters: two of them characterize the representation of S U (∞) , a dimensionful parameter arises from the possibility of comparing representations of S U (∞) by different subsystems, and the fourth parameter is a measurable used as time registered by an arbitrary subsystem chosen as a quantum clock. It introduces a relative dynamics for subsystems, formulated by a symmetry-invariant effective Lagrangian defined on the (3+1)D space of the continuous parameters. At lowest quantum order, the Lagrangian is a Yang–Mills field theory for both S U (∞) and internal symmetries. We identify the common S U (∞) symmetry and its interaction with gravity. Consequently, S U (∞) -QGR predicts a spin-1 mediator for quantum gravity (QGR). Apparently, this is in contradiction with classical gravity. Nonetheless, we show that an observer who is unable to detect the quantumness of gravity perceives its effect as curvature of the space of average values of the continuous parameters. We demonstrate Lorentzian geometry of this emergent classical spacetime. [ABSTRACT FROM AUTHOR]

In certain established approaches to quantum gravity, such as causal set theory and causal dynamical triangulations, discrete spacetime structure is taken to be a primary feature, not a secondary effect of "quantizing" a pre-existing classical continuum-based theory, as is done in approaches such as string theory and loop quantum gravity. For a priori discrete models, the full quantum theory is often obtained via some version of Feynman's sum-over-histories approach, in which each "history" is a discrete object viewed as a classical spacetime. Counterintuitive physical scenarios such as Schrödinger's cat or the grandfather paradox are typically associated with either quantum effects or causality violations, but we demonstrate that equally bizarre scenarios can arise at a purely classical level in the discrete causal context due to symmetry considerations. In particular, the graph-theoretic phenomenon of pseudosimilarity leads to situations in which alternative events occurring at physically distinguishable locations in the universe can cause different parts of the universe to "swap identities" in a fugue-like manner alien to continuum-based theories. This phenomenon is perhaps best understood as an extension of the relativity principle, which we call relativity of identity. [ABSTRACT FROM AUTHOR]

In this work, the matching of the Vilkovisky–DeWitt effective action of quantum gravity is discussedwith an example of an ultra‐violet complete theory of quantum gravity. The authors show how this matching enables a calculation of the local Wilson coefficients of the effective action. Several examples in string theory are provided. Moreover, the matching conditions within the context of the swampland program are discussed. [ABSTRACT FROM AUTHOR]

The equivalence principle, being one of the building blocks of general relativity, seems to be crucial for analysis of quantum effects in gravity. In this paper we consider the relation between the equivalence principle and the consistency of quantum information processing in gravitational field. We propose an analysis with a looped evolution consisting of steps both in the gravitational field and in the accelerated reference frame. We show that without the equivalence principle the looped quantum evolution cannot be unitary and looses its consistency. For this reasoning the equivalence principle is formulated in terms of the gauge transformations and is analyzed for particles acquiring an appropriate phase associated with the action over the looped path. In consequence, to keep consistency of quantum operations in gravitational field, it is required to keep a quantum variant of the equivalence principle. This proves importance of the quantized version of this fundamental gravitational principle for quantum information processing. [ABSTRACT FROM AUTHOR]

We construct and study properties of an infinite dimensional analog of Kahane's theory of Gaussian multiplicative chaos (Kahane in Ann Sci Math Quebec 9(2):105-150, 1985). Namely, if H T (ω) is a random field defined w.r.t. space-time white noise B ˙ and integrated w.r.t. Brownian paths in d ≥ 3 , we consider the renormalized exponential μ γ , T , weighted w.r.t. the Wiener measure P 0 (d ω) . We construct the almost sure limit μ γ = lim T → ∞ μ γ , T in the entire weak disorder (subcritical) regime and call it subcritical GMC on the Wiener space. We show that μ γ { ω : lim T → ∞ H T (ω) T (ϕ ⋆ ϕ) (0) ≠ γ } = 0 almost surely, meaning that μ γ is supported almost surely only on γ -thick paths, and consequently, the normalized version is singular w.r.t. the Wiener measure. We then characterize uniquely the limit μ γ w.r.t. the mollification scheme ϕ in the sense of Shamov (J Funct Anal 270:3224–3261, 2016) – we show that the law of B ˙ under the random rooted measure Q μ γ (d B ˙ d ω) = μ γ (d ω , B ˙) P (d B ˙) is the same as the law of the distribution f ↦ B ˙ (f) + γ ∫ 0 ∞ ∫ R d f (s , y) ϕ (ω s - y) d s d y under P ⊗ P 0 . We then determine the fractal properties of the measure around γ -thick paths: - C 2 ≤ lim inf ε ↓ 0 ε 2 log μ ^ γ (‖ ω ‖ < ε) ≤ lim sup ε ↓ 0 sup η ε 2 log μ ^ γ (‖ ω - η ‖ < ε) ≤ - C 1 w.r.t a weighted norm ‖ · ‖ . Here C 1 > 0 and C 2 < ∞ are the uniform upper (resp. pointwise lower) Hölder exponents which are explicit in the entire weak disorder regime. Moreover, they converge to the scaling exponent of the Wiener measure as the disorder approaches zero. Finally, we establish negative and L p ( p > 1 ) moments for the total mass of μ γ in the weak disorder regime. [ABSTRACT FROM AUTHOR]

We discuss the challenges that the standard (Humean and non-Humean) accounts of laws face within the framework of quantum gravity where space and time may not be fundamental. This paper identifies core (meta)physical features that cut across a number of quantum gravity approaches and formalisms and that provide seeds for articulating updated conceptions that could account for QG laws not involving any spatio-temporal notions. To this aim, we will in particular highlight the constitutive roles of quantum entanglement, quantum transition amplitudes and quantum causal histories. These features also stress the fruitful overlap between quantum gravity and quantum information theory. [ABSTRACT FROM AUTHOR]

For an arbitrary dimension n$n$, we study: the polyharmonic Gaussian field hL$h_L$ on the discrete torus TLn=1LZn/Zn$\mathbb {T}^n_L = \frac{1}{L} \mathbb {Z}^{n} / \mathbb {Z}^{n}$, that is the random field whose law on RTLn$\mathbb {R}^{\mathbb {T}^{n}_{L}}$ given by cne−bn(−ΔL)n/4h2dh,$$\begin{equation*} \hspace*{-4.5pc}c_n\, \text{e}^{-b_n{\left\Vert (-\Delta _L)^{n/4}h\right\Vert} ^2} dh, \end{equation*}$$where dh$dh$ is the Lebesgue measure and ΔL$\Delta _{L}$ is the discrete Laplacian; the associated discrete Liouville quantum gravity (LQG) measure associated with it, that is, the random measure on TLn$\mathbb {T}^{n}_{L}$ μL(dz)=expγhL(z)−γ22EhL(z)dz,$$\begin{equation*} \hspace*{-7.5pc}\mu _{L}(dz) = \exp {\left(\gamma h_L(z) - \frac{\gamma ^{2}}{2} \mathbf {E} h_{L}(z) \right)} dz, \end{equation*}$$where γ$\gamma$ is a regularity parameter. As L→∞$L\rightarrow \infty$, we prove convergence of the fields hL$h_L$ to the polyharmonic Gaussian field h$h$ on the continuous torus Tn=Rn/Zn$\mathbb {T}^n = \mathbb {R}^{n} / \mathbb {Z}^{n}$, as well as convergence of the random measures μL$\mu _L$ to the LQG measure μ$\mu$ on Tn$\mathbb {T}^n$, for all γ<2n$\left|\gamma \right| < \sqrt {2n}$. [ABSTRACT FROM AUTHOR]

Recently, it was shown that if two distant test masses, each in a spatially superposed quantum state, become entangled due to their mutual gravitational interaction, then this entanglement could serve as evidence of the quantum nature of gravity. We extend this treatment to a many-body system in a general setup and study the entanglement properties of the time-evolved state. We exactly compute the time-dependent I-concurrence for every bipartition and obtain the necessary and sufficient condition for the creation of genuine many-body entanglement. We further show that this entanglement is of generalised GHZ type when certain conditions are met. We also evaluate the amount of multipartite entanglement in the system using a set of generalised Meyer-Wallach measures. [ABSTRACT FROM AUTHOR]

In this study, we explore various essential aspects of a noncommutative theory that incorporates space deformation. Through the Extended Gravitational Decoupling (EGD) approach within the Strong Energy Condition (SEC), we investigate the gravitational decoupling method to obtain static black hole solutions that satisfy Einstein's field equations with a vacuum tensor. The analysis concentrates on the thermodynamics of the static solution, examining and deriving expressions for various thermodynamic quantities. This investigation explores how temperature, free energy, and specific heat depend on the horizon radius, considering different values for both hairy and noncommutative parameters. The study suggests that thermodynamically, smaller hairy black holes exhibit greater stability compared to larger ones. It also reveals a nontrivial relationship between the horizon radius, temperature range, and specific values of the hairy parameters for static hairy black holes when considered in thermodynamic equilibrium with their Hawking radiation. The discussion extends to the implications of the first law of black hole thermodynamics in the context of the noncommutative hairy case. [ABSTRACT FROM AUTHOR]

We extend the analytic description of complex no-boundary solutions in the context of inflation to large field models. We discuss the Kontsevich–Segal–Witten (KSW) criterion and find it is satisfied in small field models, while in large field models it depends on an integral involving V ′ (ϕ) over the range of inflation. It follows that although particular models are ruled out, e.g. quadratic inflation, the criterion does not truly constrain inflationary phenomenology since any inflation potential can be completed beyond observable scales so as to satisfy KSW. [ABSTRACT FROM AUTHOR]

Ellipse fitting is a technique which is used to extract differential phase in cold-atom interferometers, particularly in situations where common-mode noise needs to be suppressed. We use numerical simulation to investigate errors in the ellipse fitting process; specifically, errors due to the presence of additive noise, linear drift in ellipse offset and amplitude, as well as an error that can arise from fringe normalisation. Errors are found to manifest in two ways: bias in the ellipse phase measurement and incomplete suppression of common mode phase noise. We quantify these errors for three different ellipse fitting algorithms and discuss the applicability of these results to future cold atom sensors. [ABSTRACT FROM AUTHOR]

We point out that dark matter and dark energy arise naturally in a recently proposed model of combinatorial quantum gravity. Dark energy is due to the ground-state curvature at finite coupling, dark matter arises from allotropy in the discrete structure of space-time. The stable structure of the space-time 'crystal' represents the curved background, the coexisting metastable allotropes of higher curvature and energy are natural candidates for dark matter. We thus suggest that dark energy and dark matter are two manifestation of quantum gravity. [ABSTRACT FROM AUTHOR]

The detectors of astrophysical gravitational waves are based on optical interferometers. There is not yet an analogue of a quantum mechanical atomic detector of photons for the detection of gravitational waves. I point out the remarkable fact that the already observed pico-electron volt quantization of energy levels of ultra-cold neutrons, gravitationally bound to the Earth in a bouncing mode, fortuitously coincide with the range of energies of the hypothetical quanta of astrophysical gravitational waves. Thus, it is feasible to use a cold-neutron bouncing reservoir as a novel quantum sensor for directly detecting astrophysical gravitational waves, in a wide frequency band. These considerations also lead us to the discovery that many detected signals in interferometric detectors like LIGO correspond to the energy of a single gravitational quantum or less. This surprising finding enables a decisive experimental test of quantum gravity. [ABSTRACT FROM AUTHOR]

In this paper, we consider the single-parameter ℛ + c ℛ 2 gravitational action and use constraints from astrophysics and the laboratory to derive a natural relation between the coefficient c and the value of the cosmological constant. We find that the renormalization of c from the energy of the inflationary phase to the infrared, where the acceleration of the expansion of the universe takes place, is correlated with the evolution of the vacuum energy. Our results suggest that the coefficient of the ℛ 2 term may provide an unexpected bridge between high-energy physics and cosmological phenomena such as inflation and dark energy. [ABSTRACT FROM AUTHOR]

In this essay, we argue that certain aspects of the measurement require revision in Quantum Gravity. Using entropic arguments, we propose that the number of measurement outcomes and the accuracy (or the range) of the measurement are limited by the entropy of the black hole associated with the observer's scale. This also implies the necessity of modifying the algebra of commutation relationships to ensure a finite representation of observables, changing the Heisenberg Uncertainty Principle in this manner. [ABSTRACT FROM AUTHOR]

Through use of the Pauli–Villars regulator procedure, we construct a second- plus fourth-order derivative theory of gravity that serves as an ultraviolet completion of standard second-order derivative quantum Einstein gravity that is ghost-free, unitary and power-counting renormalizable. [ABSTRACT FROM AUTHOR]

Recent experimental progresses in controlling classical and quantum fluids have made it possible to realize acoustic analogs of gravitational black holes, where a flowing fluid provides an effective spacetime on which sound waves propagate, demonstrating Hawking-like radiation and superradiance. We propose the exciting possibility that new hydrodynamic systems might provide insights to help resolve mysteries associated with quantum gravity, including the black hole information-loss paradox and the removal of spacetime singularities. [ABSTRACT FROM AUTHOR]

In this essay, it is proven that, in a self-consistent semiclassical theory of gravity, the asymptotically measured orbital periods of test particles around central compact objects are fundamentally bounded from below by the compact universal relation T ∞ ≥ 2 π e ℏ G c 2 m e 2 [here { m e , e } are, respectively, the proper mass and the electric charge of the electron, the lightest charged particle]. The explicit dependence of the lower bound on the fundamental constants { G , c , ℏ } of gravity, special relativity, and quantum theory suggests that it provides a rare glimpse into the yet unknown quantum theory of gravity. [ABSTRACT FROM AUTHOR]

As famously observed by Ooguri and Vafa nearly 20 years ago, scalar field moduli spaces in quantum gravity appear to exhibit various universal features. For instance, they seem to be infinite in diameter, have trivial fundamental group, and feature towers of massive particles that become light in their asymptotic limits. In this paper, we explain how these features can be reformulated in more modern language using generalized notions of global symmetries. Such symmetries are ubiquitous in nongravitational quantum field theories, but it is widely believed that they must be either gauged or broken in quantum gravity. In what follows, we will see that the observations of Ooguri and Vafa can be understood heuristically as consequences of such gauging or breaking. [ABSTRACT FROM AUTHOR]

We expect the final theory of gravity to have more symmetries than we suspect and our research points in this direction. To start with, standard general coordinate invariance can be extended to complex holomorphic general coordinate transformations. This is possible by introducing a non-Riemannian measure of integration (NRMI) and where we avoid the nonholomorphic standard − g measure of integration. Second, locally signed coordinate transformations where the Jacobian changes sign locally but the Jacobian approaches one asymptotically should be symmetries of Nature. This is unlike globally signed transformations that produce a change of boundary conditions, like in the cases of global parity and global time reversal, which are not symmetries of Nature. The holomorphic extension can regularize the regions of spacetime where the Jacobian changes sign. Consequences for Quantum Gravity are discussed. [ABSTRACT FROM AUTHOR]

Effective field theories which describe the coupling between gravity and matter fields have recently been extended to include terms with operators of non-minimal mass dimension. These terms preserve the usual gauge symmetries but may violate local Lorentz and diffeomorphism invariance. The number of possible terms in the field theory explodes once one allows for non-minimal operators, with no criterion to choose between them. We suggest as such a criterion to focus on terms which violate Lorentz invariance via a (pseudo)vector background field, leaving a number of possible terms in the Higgs, gauge, and gravitational sectors. Further study of these terms is motivated by the proposed correspondence between the general effective theory for Lorentz violation and emergent Lorentz symmetry in condensed-matter systems, which is mostly unexplored for higher mass dimension operators and couplings to gauge fields and gravity. We suggest bounds in the Higgs sector and we show that some of the coefficients in the gauge sector vanish at one loop, whereas others have bounds which are comparable with those suggested by Kostelecký and Li for coefficients in Lorentz-violating QCD and QED coupled to quarks. We also find new bounds in the gravitational sector by considering the Robertson--Walker model. Finally, we discuss the special case where only diffeomorphism invariance is spontaneously broken and explain why it does not allow for non-trivial Nambu--Goldstone modes. [ABSTRACT FROM AUTHOR]