Article
Astronomy & Astrophysics
Joshua Baines, Matt Visser
Summary: Despite decades of research, there is still no widely accepted method to derive the Kerr solution for rotating black holes without significant computational effort. This paper proposes using a non-ortho-normal tetrad and oblate spheroidal coordinates to simplify the angular dependence, separating mass and rotation dependencies in the solution and making it less mysterious.
CLASSICAL AND QUANTUM GRAVITY
(2022)
Article
Physics, Multidisciplinary
Chaitra Chooda Chalavadi, N. S. Kavya, V. Venkatesha
Summary: The aim of this manuscript is to investigate the existence of spherically symmetric wormhole solutions in the context of extended symmetric teleparallel gravity by involving some aspects of non-commutative geometry. The study reveals important properties of the shape function and features of exotic matter, leading to concluding remarks.
EUROPEAN PHYSICAL JOURNAL PLUS
(2023)
Article
Physics, Multidisciplinary
Xinzhi Zhao, Chengjie Zhang
Summary: The theoretical framework for the uncertainty relation of non-Hermitian operators is presented, and a simplified experimental measurement scheme is proposed. The research results are of great significance for a deeper understanding of the role of non-Hermitian operators in uncertainty relations.
FRONTIERS IN PHYSICS
(2022)
Article
Astronomy & Astrophysics
Roberto Casadio, Wenbin Feng, Ibere Kuntz, Fabio Scardigli
Summary: This article discusses the concepts of minimum geometrical length and minimum length scale in quantum field theory, using correlation functions obtained from in-in and in-out amplitudes. The in-in propagator for metric perturbations does not admit the former, while the in-out Feynman propagator shows the emergence of the latter. The article then exhibits a connection between the Feynman propagator of quantum field theories of gravity and the deformation parameter 80 of the generalized uncertainty principle (GUP), allowing for the determination of an exact expression for 80 in terms of the residues of the causal propagator. A conjecture is made about the correspondence between the non-renormalizability of (some) theories of gravity and the existence of a minimum length scale, suggesting that non-renormalizable theories are self-complete and finite. The role of the sign of the deformation parameter is further discussed by considering the implementation of the GUP on the lattice.
Article
Astronomy & Astrophysics
Keith Doore, Erik B. Monson, Rafael T. Eufrasio, Bret D. Lehmer, Kristen Garofali, Antara Basu-Zych
Summary: This article introduces an updated version of the galaxy spectral energy distribution (SED) fitting code called "Lightning", which can model X-ray to submillimeter observations. The Lightning code includes options to incorporate contributions from stellar populations, dust attenuation and emission, and active galactic nuclei (AGNs). Various algorithms have been included to fit the models to observations and sample parameter posteriors. Several examples are presented to demonstrate the capabilities of Lightning, including deriving stellar properties of M81, constraining properties of distant AGNs using X-ray emission, rectifying attenuation effects on the star formation rate of NGC 4631, comparing Lightning to other SED-fitting codes for NGC 628, and comparing Lightning and CIGALE for a distant AGN. Lightning is an open-source application developed in IDL and is available at https://github.com/rafaeleufrasio/lightning.
ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES
(2023)
Article
Engineering, Mechanical
Clemens Huebler, Paul Gardner, Marlene Wolniak
Summary: In recent years, model updating for structural dynamics has gained popularity, with the aim of calibrating finite element models and detecting damage in structural health monitoring. Bayesian model updating has become increasingly popular as it accounts for uncertainties. Likelihood-free approaches, such as Bayesian history matching (BHM), have been proposed as an alternative to exact Bayesian model updating. However, they can become inaccurate for highly non-linear or discontinuous problems. In this work, a new approach called non-implausibility-motivated optimization (NIMO) is introduced, which combines global optimization and Gaussian process regression (GPR). The NIMO approach yields more robust results compared to BHM and has manageable computing times.
MECHANICAL SYSTEMS AND SIGNAL PROCESSING
(2023)
Article
Physics, Multidisciplinary
F. Bagarello
Summary: In this paper, we primarily discuss some aspects of the Heisenberg uncertainty relation from the perspective of non self-adjoint operators. We derive some equivalence results and refine the inequality, as well as discuss relevant examples. Additionally, we initiate a dynamical analysis of the relation in connection with gamma-dynamics and gamma-symmetries, and explore the role of different scalar products in our analysis. The case of self-adjoint operators is recovered as a special case within our general settings.
JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL
(2023)
Article
Computer Science, Artificial Intelligence
Haonan Lu, Hailin Hu, Xiaodong Lin
Summary: This article introduces a knowledge graph embedding method called DensE to improve the modeling scheme for complex composition patterns of relations. The method decomposes each relation into a rotation operator and a scaling operator, and has high computational efficiency and expressiveness. Experimental results show that DensE performs well in missing link prediction and provides geometric interpretations of relational patterns.
Article
Physics, Particles & Fields
Marija Dimitrijevic Ciric, Nikola Konjik, Andjelo Samsarov
Summary: This paper establishes another example of the implicit duality within the structure of noncommutative (NC) theories through perturbation in the first order of the Seiberg-Witten expansion. The model studied relates a noncommutative U(1)(*) gauge field to a noncommutative scalar field and to a classical Reissner-Nordstrom (RN) geometry, and it is shown to be completely equivalent to the commutative U(1) gauge theory coupled to a commutative scalar field and a classical geometry. The results obtained contribute to a deeper understanding of the dynamics of spin 1/2 fields on curved backgrounds with a persistent noncommutative structure.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Physics, Multidisciplinary
Pritam Chattopadhyay, Tanmoy Pandit, Ayan Mitra, Goutam Paul
Summary: This study analyzed the efficiency of quantum heat cycles and refrigerators using various quantum systems as working mediums. It was found that different working substances and space structures can impact efficiency, with higher values of the non-commutative parameter boosting the efficiency of quantum heat engines.
PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS
(2021)
Article
Astronomy & Astrophysics
Giuseppe Gaetano Luciano, Jaume Gine
Summary: In this study, Tsallis Cosmology is used to investigate thermodynamic gravity and derive modified Friedmann equations. The findings reveal that corrections due to non-extensivity have an impact on the evolution of the Hubble function during the radiation-dominated epoch. Consequently, the mass density and pressure content of the Universe undergo non-trivial modifications, providing a viable mechanism for baryogenesis.
Article
Mechanics
Paolo Muratore-Ginanneschi, Luca Peliti
Summary: We analyze Furth's classical uncertainty relations from 1933 using modern stochastic differential equations. Our focus is on their application to non-equilibrium classical statistical mechanics. We show that Furth's uncertainty relations are inherent in martingales in diffusion processes. This implies a lower bound on the fluctuations in current velocities of entropic quantifiers in stochastic thermodynamics. Additionally, we extend Furth's relations to piecewise deterministic processes and generalize our results to general Markov processes.
JOURNAL OF STATISTICAL MECHANICS-THEORY AND EXPERIMENT
(2023)
Article
Astronomy & Astrophysics
Dawood Kothawala
Summary: A generic implication of incorporating gravitational effects in the analysis of quantum measurements is the existence of a zero-point length of spacetime. The quantum spacetime should be reconstructed from non-local bi-tensors, revealing the subtle interplay between non-locality and the limit when G (h) over bar /c(3) -> 0. The emergent gravity paradigm, characterized by an entropy functional, arises as a fundamentally non-local quantum spacetime. This paper describes the flow of metric with respect to Planck length and proposes a novel action.
INTERNATIONAL JOURNAL OF MODERN PHYSICS D
(2023)
Article
Physics, Multidisciplinary
Seyed Amin Khorram-Hosseini, Hossein Panahi, Saber Zarrinkamar
Summary: We investigate the modification of linear momentum based on non-locality in the framework of generalized uncertainty principle. The deformed commutation relation between position and momentum is derived, and its effects on the behavior of nonrelativistic systems are analyzed analytically. The extreme values of energy and wavelength in terms of Planck scale are calculated and compared with existing results.
EUROPEAN PHYSICAL JOURNAL PLUS
(2023)
Article
Oncology
Malcolm H. Squires, Erin E. Donahue, Michelle L. Wallander, Sally J. Trufan, Reilly E. Shea, Nicole F. Lindholm, Joshua S. Hill, Jonathan C. Salo
Summary: The study used the NSQIP dataset to investigate the factors associated with length of stay and early discharge in cancer patients undergoing colectomy. Factors such as independent functional status, minimally invasive approach, and absence of ostomy or additional bowel resection were significantly associated with shorter hospital stays. A model based on perioperative variables could be developed to identify patients eligible for early discharge and efforts should be focused on optimizing modifiable risk factors to decrease overall hospital stays.
Article
Astronomy & Astrophysics
Stefano Viaggiu
INTERNATIONAL JOURNAL OF MODERN PHYSICS D
(2017)
Article
Physics, Multidisciplinary
Francesco Fidaleo, Stefano Viaggiu
PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS
(2017)
Article
Physics, Mathematical
Fassari Silvestro, Rinaldi Fabio, Viaggiu Stefano
INTERNATIONAL JOURNAL OF GEOMETRIC METHODS IN MODERN PHYSICS
(2018)
Article
Physics, Nuclear
S. Viaggiu
INTERNATIONAL JOURNAL OF MODERN PHYSICS A
(2018)
Article
Astronomy & Astrophysics
Stefano Viaggiu
INTERNATIONAL JOURNAL OF MODERN PHYSICS D
(2018)
Article
Astronomy & Astrophysics
S. Viaggiu
CLASSICAL AND QUANTUM GRAVITY
(2018)
Article
Physics, Multidisciplinary
Stefano Viaggiu
EUROPEAN PHYSICAL JOURNAL PLUS
(2018)
Article
Mathematics, Applied
S. Fassari, F. Rinaldi, S. Viaggiu
MATHEMATICAL PHYSICS ANALYSIS AND GEOMETRY
(2019)
Article
Physics, Multidisciplinary
S. Viaggiu
Article
Physics, Multidisciplinary
S. Viaggiu
FOUNDATIONS OF PHYSICS
(2019)
Article
Astronomy & Astrophysics
S. Viaggiu
Summary: After critically reviewing the generalized uncertainty principle (GUP) applied to compact objects, a new texture of Heisenberg uncertainty principle in curved spacetimes (CHUP) was proposed. The study found that general relativistic effects strongly reduce the Newtonian limit for very compact astrophysical objects, with the maximum mass decreasing with increasing compactness of the star.
CLASSICAL AND QUANTUM GRAVITY
(2021)
Article
Astronomy & Astrophysics
S. Viaggiu
Summary: This paper explores the nature of the cosmological constant as arising from quantum fluctuations, with noncommutative effects generating fluctuations at Planckian scales that are then watered down at larger scales up to a decoherence scale LD. By adopting a renormalization group approach, a connection is made between the observed cosmological constant and the expected one, with the decoherence scale LD being naturally identified with the value mu(D). Mimicking a renormalization group approach, a technique to formally obtain a nontrivial infrared fixed point at mu = mu(D) in the model is presented.
INTERNATIONAL JOURNAL OF MODERN PHYSICS D
(2021)
Article
Physics, Mathematical
Stefano Viaggiu
Summary: In this paper, the perturbative regime in the static patch of de Sitter metric is studied using the Regge-Wheeler formalism. It is shown that the perturbative regime can be extended up to the cosmological horizon by introducing the tortoise coordinate r. The axial perturbative equations are analyzed, and suitable boundary conditions are found to extend the perturbative regime. Short distance effects are explored by applying the boundary conditions of a quantum 3D harmonic oscillator to the obtained equation, resulting in a discrete spectrum that may indicate quantum behavior of gravitons.
INTERNATIONAL JOURNAL OF GEOMETRIC METHODS IN MODERN PHYSICS
(2022)
Article
Astronomy & Astrophysics
S. Viaggiu
Summary: Motivated by the search for physically viable rotating sources, the authors propose a new class of anisotropic rotating solutions. The energy-momentum tensor is composed of anisotropic matter with nonvanishing energy flow and vanishing viscosity. These solutions can be used to find new possible sources for the Kerr metric, obtain regular black hole solutions, and study galaxies with a central rotating black hole and a halo of dark matter. As an example, a five-parameter class of solutions representing a traversable wormhole smoothly matched to the Kerr metric is obtained.
INTERNATIONAL JOURNAL OF MODERN PHYSICS D
(2023)
Article
Astronomy & Astrophysics
Stefano Viaggiu
CLASSICAL AND QUANTUM GRAVITY
(2017)