Fri - 01/09/26

**Title:

      From Loop Quantum Gravity to a Theory of Everything**  - **Authors:** Adrian P. C. Lim  - **Subjects:** Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)  - **Arxiv link:** [https://arxiv.org/abs/](https://arxiv.org/abs/)  - **Abstract**  Witten described how a path integral quantization of Wilson Loop observables will define Jones polynomial type of link invariants, using the Chern-Simons gauge theory in $\mathbb{R}^3$. In this gauge theory, a compact Lie group ${\rm G}$, together with a representation of its Lie Algebra $\mathfrak{g}$, describe the symmetry group and fundamental forces acting on the particles respectively. However, it appears that this theory might be part of a bigger theory. We will incorporate this theory into the Einstein-Hilbert theory, which when reformulated and quantized using a ${\rm SU}(2) \times {\rm SU}(2)$ gauge group, gives us a quantized theory of gravity in $\mathbb{R}^4$. In this theory, we can quantize area, volume and curvature into quantum operators. By using both the Chern-Simons and Einstein-Hilbert action, we will write down a path integral expression, and compute the Wilson Loop observable for a time-like hyperlink in $\mathbb{R}^4$, each component loop is coloured with a representation for the Lie Algebra $\mathfrak{g} \times [\mathfrak{su}(2) \times \mathfrak{su}(2)]$, unifying the fundamental forces with gravity. This Wilson Loop observable can be computed using link diagrams, and it can be written as a state model, satisfying a Homfly-type skein relations. We will show that the Wilson Loop observable remains an eigenstate for the quantum operators corresponding to spin curvature, but it is not an eigenstate for the area and volume quantized operators, unless the representation for $\mathfrak{g}$ is trivial. This implies that in the Planck scale where quantum gravity is important, we see that all the particles are indistinguishable, hence the fundamental forces disappear and only interaction between matter and space-time remains.

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  1. [] - Title: Reconstructing Minkowski geometry from causal separations - Chenyang Amy Hu (Westview High School, Carnegie Mellon University), David A. Meyer (UC San Diego), Eleanor J. Q. Meyer (The Bishop’s School)

Thu - 01/08/26

There is no new related paper today

**Title:

      Discrete gravitational diagram technique in the soft synchronous gauge**  - **Authors:** V.M. Khatsymovsky  - **Subjects:** Subjects: General Relativity and Quantum Cosmology (gr-qc)  - **Arxiv link:** [https://arxiv.org/abs/](https://arxiv.org/abs/)  - **Abstract**  This paper develops our work on the consequences of the Regge calculus, where some edge length scale arises as an optimal starting point of the perturbative expansion with taking into account a bell-shaped form of the measure obtained using functional integration over connection. A "hypercubic" structure is considered (some variables are frozen), it is described by the metric $g_{\lambda \mu}$ at the sites. The edge length scale as some maximum point of the measure is $\sim \eta^{1 / 2}$, where $\eta$ defines the free factor like $ ( - \det \| g_{\lambda \mu} \| )^{ \eta / 2}$ in the measure and should be a large parameter to ensure true action upon integration over connection. A priori, the perturbative expansion may contain increasing powers of $\eta$, but this does not happen for the starting point inside some neighborhood of the maximum point of the measure, and it does happen outside this neighborhood. This appears to be a dynamic mechanism for establishing the edge length scale. We use a discrete version of the soft synchronous gauge in the principal value type prescription we discuss in a recent paper arXiv:2601.02181. This allows one to fix the timelike length scale at a low level for which the measure is known in closed form. This gauge is considered together with a refined finite-difference form of the action to match the analytical properties of the propagator to the continuum case.

Wed - 01/07/26

There is no new related paper today

**Title:

      Discrete vs continuum gravitational diagrams in the soft synchronous gauge**  - **Authors:** V.M. Khatsymovsky  - **Subjects:** Subjects: General Relativity and Quantum Cosmology (gr-qc)  - **Arxiv link:** [https://arxiv.org/abs/](https://arxiv.org/abs/)  - **Abstract**  Due to the non-renormalizability of continuum gravity, the perturbative expansion makes sense, say, for its discrete simplicial (Regge calculus) version. The finite-difference form of the gravity action has diffeomorphism symmetry at leading order over metric variations from site to site, and we add a term bilinear in $n^\lambda ( g_{\lambda \mu} - g_{\lambda \mu}^{(0 ) } )$, $n^\lambda = [ 1, - \varepsilon ( \Delta^{(s ) \alpha } \Delta^{(s ) }_\alpha )^{- 1} \Delta^{(s ) \beta } ]$, to "softly" fix the synchronous gauge $g_{0 \lambda} = g_{0 \lambda }^{(0 ) } = - \delta_{0 \lambda}$ at $\varepsilon \to 0$, thereby resolving singularities at $p_0 = 0$. For the symmetric form of the derivative $\Delta^{(s ) }_\lambda$, the propagator has a graviton pole at $p_0$ close to 0 or $\pm \pi$ at small $p_\alpha$. This pole doubling compared to the continuum case is removed by using the action $\check{S}_{\rm g}$ with the usual derivative $\Delta_\lambda = \exp ( i p_\lambda ) - 1$ instead of $\Delta^{(s ) }_\lambda = i \sin p_\lambda$ in some terms, including in the $k$ part of some term, and $\Delta^{(s ) }_\lambda$ in the $1 - k$ part of that term. Given the propagator $\check{G} ( n, \overline{n} )$, we form the principal value type propagator $\frac{1}{2} [ \check{G} ( n, n ) + \check{G} ( \overline{n}, \overline{n} ) ]$ by analytically continuing from real $n$. Singularities are roughly resolved as $p_0^{-j} \Rightarrow [ (p_0 + i \varepsilon )^{-j} + (p_0 - i \varepsilon )^{-j} ] / 2$. We find that it is $k = 1$ that provides this prescription to properly work and match the continuum case. The gauge-fixing term required for this propagator and its finiteness are considered; the ghost contribution is found to vanish at $\varepsilon \to 0$. The results are used for the diagram technique in our recent paper. The calculations are illustrated by the electromagnetic (Yang-Mills) case.
  1. [] - Title: Regular Black Holes in Quasitopological Gravity: Null Shells and Mass Inflation - Valeri P. Frolov, Andrei Zelnikov

Tue - 01/06/26

**Title:

      Gravitation and Spacetime: Emergent from Spinor Interactions -- How?**  - **Authors:** Martin Rainer  - **Subjects:** Subjects: General Relativity and Quantum Cosmology (gr-qc)  - **Arxiv link:** [https://arxiv.org/abs/](https://arxiv.org/abs/)  - **Abstract**  Newtonian gravity arises as the nonrelativistic, static, weak-field limit of some Lorentzian spacetime geometry solving the generally covariant Einstein equations for a given matter field configuration. Spacetime geometry has a local description in the spinor basis of Penrose. The breakdown of relativistic quantum (field) theory at small distances suggests that, the Lorentzian geometry is to be modified below some regularization length. The thermodynamic correspondence, e.g. for black holes or other horizons, indicates that, Lorentzian spacetime is an emergent geometric description of an ensemble of more fundamental constituents. The independent derivations of the area law of the Bekenstein-Hawking entropy by string theory and loop quantum gravity show that, (some) properties of spacetime do not depend on the nature of its fundamental constituents (in leading order). Whether, on a fundamental scale, spacetime gravity has its own classical or quantum constituents (like e.g. in loop quantum gravity), or it is just an effective theory, deriving from expectation values of quantum matter operators (like in spinor gravity or causal fermion systems), this is still open. We compare some very different classical and quantum approaches to spacetime geometry, all deriving in one way or another from spinors, and comment on questions for future research in order to clarify their relations. We propose that both, the causal structure and the spin networks for generation of discrete geometry arise via projection from all particle spinors (fermionic and bosonic) within a causal double cone region and their spin interwining interaction events onto a spatial section of this double cone region.

There is no new related paper today

Mon - 01/05/26

**Title:

      Signatures of Quantum-Corrected Black Holes in Gravitational Waves from Periodic Orbits**  - **Authors:** Fazlay Ahmed, Qiang Wu, Sushant G Ghosh, Tao Zhu  - **Subjects:** Subjects: General Relativity and Quantum Cosmology (gr-qc)  - **Arxiv link:** [https://arxiv.org/abs/](https://arxiv.org/abs/)  - **Abstract**  We investigate gravitational wave emission from periodic timelike orbits of a test particle around a loop quantum gravity-inspired Schwarzschild black hole. The spacetime is characterised by a holonomy-correction parameter that modifies the radial metric component while preserving asymptotic flatness and the classical location of the horizon. The bound geodesics are systematically classified using the zoom--whirl representation labelled by three integers $(z,w,v)$. Gravitational waveforms are computed within a numerical framework that combines exact geodesic motion with the quadrupole approximation, which is suitable for extreme mass ratio inspirals. We demonstrate that the quantum corrections lead to distinct phase shifts, amplitude variations, and modifications to the harmonic structure of the waveforms, with increasingly complex features for orbits with larger zoom numbers. The corresponding frequency spectra and characteristic strain peak, which fall within the millihertz band, are within the sensitivity ranges of space-based detectors such as LISA, Taiji, and TianQin. For specific orbital configurations and values of the quantum-correction parameter, the characteristic strain exceeds the projected detector noise, indicating potential observability. Our results demonstrate that gravitational waves from periodic orbits provide a sensitive probe of quantum-corrected black hole spacetimes in the strong-field regime.

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