Article
Chemistry, Multidisciplinary
Richard S. Graham, Richard J. Wheatley
Summary: Accurate potential energy surfaces (PES) are required for predicting thermophysical properties from molecular principles. This study presents a widely-applicable method that produces first-principles PES using Gaussian Processes (GP) as a machine learning technique. The method accurately interpolates three-body non-additive interaction data and does not require modification for different molecules. It produces highly accurate interpolation from fewer training points and enables more accurate ab initio calculations. The method is exemplified by computing the PES for CO2-Ar mixtures, which allows for accurate first-principles predictions of various thermophysical properties.
CHEMICAL COMMUNICATIONS
(2022)
Article
Physics, Particles & Fields
Ajay Bassi, Shahnawaz A. Adil, Manvendra Pratap Rajvanshi, Anjan A. Sen
Summary: This study investigates the cosmological implications of Bimetric gravity models, finding that they are consistent with present data and exhibit significant deviations in the dark energy equation of state and skewness parameters compared to the ACDM model. Additionally, the best fit Bimetric model behaves similarly to ACDM in terms of the ISW effect.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Physics, Multidisciplinary
Arkadiusz Bochniak
Summary: This paper discusses a class of doubled geometry models with diagonal metrics and proposes a hypothesis that treats them as modified bimetric gravity theories.
JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL
(2022)
Article
Astronomy & Astrophysics
Ioannis D. Gialamas, Kyriakos Tamvakis
Summary: Bimetric gravity is a theory that proposes the existence of two interacting and dynamic metric tensors. Its spectrum includes a massless and a massive spin-2 particle. The interactions between the two metrics are constrained to avoid the presence of the Boulware-Deser ghost. This study extends the original bimetric theory to its bimetric-affine counterpart, treating the two connections associated with Ricci scalars as independent variables. The analysis shows that the theory is free of ghosts for a wide range of interaction parameters, leaving open the possibility of a dark matter interpretation for the massive spin-2 particle.
Article
Astronomy & Astrophysics
Carlos Maldonado, Fernando Mendez
Summary: The study focuses on the early stage of universe evolution with two scale factors and interaction between causally disconnected patches. Numerical analysis shows energy transfer between sectors, providing constraints on the deformation parameter, with considerations for energy density decay before Big Bang Nucleosynthesis temperature. The study also addresses implications for nonstandard cosmologies.
Article
Engineering, Mechanical
Rami Masri, Shannon Ryan
Summary: The ballistic resistance of metallic targets with ductile hole formation can be accurately calculated using the specific cavitation energy concept. This study presents an extension to those models for targets with two in-contact layers of varying material type and thickness and provides a heuristic model for replacing the second layer with a ballistically-equivalent layer of material identical to the first layer.
INTERNATIONAL JOURNAL OF IMPACT ENGINEERING
(2023)
Article
Astronomy & Astrophysics
Mostafizur Rahman, Anjan A. Sen, Sunil Singh Bohra
Summary: This paper presents an exact solution within the ghost-free bimetric gravity theory, which represents a traversable Lorentzian wormhole violating the weak energy condition near its throat. The presence of arbitrarily long-lived quasiresonant modes is observed in the wormhole spacetime.
Article
Astronomy & Astrophysics
Mordehai Milgrom
Summary: All existing treatments of bimetric MOND (modified Newtonian dynamics) have only considered a restricted subclass, but the scope of BIMOND is much richer. The two metrics can couple through several scalars, giving theories that have a good nonrelativistic limit. These theories can account for the dynamics of galactic systems, including gravitational lensing, and show a departure from the current understanding of MOND.
Article
Physics, Particles & Fields
Ziqi Yan
Summary: The study presents a two-dimensional nonlinear Sigma model that describes classical strings propagating in a curved spacetime background, with derived beta-functionals for the bimetric fields. Imposing worldsheet Weyl invariance at the quantum level reveals a set of gravitational field equations that dictate the dynamics of the bimetric fields in the target space.
JOURNAL OF HIGH ENERGY PHYSICS
(2021)
Article
Astronomy & Astrophysics
Arka Banerjee, Subinoy Das, Anshuman Maharana, Ravi Kumar Sharma
Summary: This paper focuses on the effects of Light Massive Relics (LiMRs) on smaller, nonlinear scales using cosmological N-body simulations. The study finds that LiMRs have distinct effects on small scales compared to the ΛCDM universe, even when the value of sigma(8) is matched between the models. Weak lensing measurements around massive clusters between 0.1 h(-1)Mpc and 10 h(-1)Mpc can be used to distinguish between ΛCDM and LiMR models. Additionally, different LiMR cosmologies can be distinguished by non-linear probes if their velocity distributions are sufficiently different.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Automation & Control Systems
Arthur Leroy, Pierre Latouche, Benjamin Guedj, Servane Gey
Summary: This paper introduces a model based on Gaussian processes (GPs) for simultaneously handling multitask learning, clustering, and prediction for multiple functional data. The model acts as a model-based clustering method for functional data and also serves as a learning step for subsequent predictions for new tasks. By considering uncertainty in both mean processes and latent clustering variables within a predictive distribution, the model improves performance when dealing with group-structured data.
JOURNAL OF MACHINE LEARNING RESEARCH
(2023)
Article
Materials Science, Multidisciplinary
Patrick L. Taylor, Gareth Conduit
Summary: Gaussian process regression machine learning with a physically-informed kernel is used to model the phase compositions of nickel-base superalloys, providing accurate predictions with quantified uncertainty and the ability to be retrained with new data.
COMPUTATIONAL MATERIALS SCIENCE
(2022)
Review
Biochemistry & Molecular Biology
Vidhi Pareek, Zhou Sha, Jingxuan He, Ned S. Wingreen, Stephen J. Benkovic
Summary: Metabolic channeling postulates that enzymes can directly transfer products to each other, increasing flux and isolating intermediates. This concept is supported by physical molecular tunnels, multi-enzyme complexes, and enzyme clusters.
Article
Astronomy & Astrophysics
Mikica Kocic
Summary: The article introduces the use of geometric mean to parametrize metrics in the Hassan-Rosen ghost-free bimetric theory and solves the initial-value problem. The parametrization based on geometric mean metric ensures the reality of the square root in the ghost-free bimetric interaction potential. It also mentions the standard n + 1 decomposition derived in a frame adapted to the geometric mean.
CLASSICAL AND QUANTUM GRAVITY
(2021)
Article
Engineering, Aerospace
Hao Peng, Xiaoli Bai
Summary: This paper introduces a new method for improving orbit prediction accuracy using machine learning, and demonstrates the potential for fusion strategies to enhance precision.
Article
Physics, Multidisciplinary
John D. Barrow, Joao Magueijo
Summary: The text introduces the concept of effective Planck parameter and discusses its dependence on the region under study, time variations, and the specific pair of observables. It also explores how the classical limit may be expected for regions beyond a certain length scale, and mentions the possibility of quantum effects in contexts where the cosmological constant remains dynamic. Additionally, it touches upon speculative cases where Planck parameters scale differently with length scales, and the potential impact of complementary concepts on thermodynamic variables like temperature and black hole entropy.
FOUNDATIONS OF PHYSICS
(2021)
Article
Astronomy & Astrophysics
Stephon Alexander, Gabriel Herczeg, Joao Magueijo
Summary: This article discusses the Fourier dual of the Hartle-Hawking wave function and its generalization beyond mini-superspace. The evaluation of this wave function depends on the symmetries of the problem and is illustrated using anisotropic Bianchi models and the Kantowski-Sachs model. An important aspect of this approach is the inclusion of quantum fluctuations in the torsion, which has significant consequences.
CLASSICAL AND QUANTUM GRAVITY
(2021)
Article
Astronomy & Astrophysics
James Page, Joao Magueijo
Summary: This study revisits a mechanism proposed by Hawking to address the cosmological constant problem and offers alternative solutions. By introducing a new action coupling the four-form field strength to the cosmological constant, a novel mechanism similar to Unimodular Gravity is presented. A theory with a similar coupling is also discussed, showing promising results and proposing new interpretations related to time and probability flux.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Joao Magueijo
Summary: The proposal suggests that cosmological time is linked to the constants of nature. Different definitions of time are explored, with the most relevant being related to the constants controlling dynamics in each epoch. Solving the Hamiltonian constraint leads to the Schrodinger equation, with normalizable superpositions and a rich structure of alternative states, including entangled constants, allowing for new phenomenology to be discovered.
Article
Astronomy & Astrophysics
Maria Mylova, Marianthi Moschou, Niayesh Afshordi, Joao Magueijo
Summary: This paper introduces a thermal bimetric model and explores its non-Gaussian features, providing precise predictions based on the characteristics of the model. These results are of great significance for future cosmological surveys.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Emma Albertini, Stephon Alexander, Gabriel Herczeg, Joao Magueijo
Summary: We revisit the problem of inflation from the perspective of the Einstein-Cartan theory, and find that the presence of torsion may reduce the barrier for tunneling and result in a quantum cosmology model that incorporates quantum fluctuations in torsion.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Michael W. Toomey, Savvas M. Koushiappas, Bruno Alexandre, Joao Magueijo
Summary: We calculate deviations in cosmological observables in a class of connection based models of quantum gravity and show that future experiments have the potential to further constrain these models, with the interesting possibility of alleviating the S8 tension.
Article
Astronomy & Astrophysics
Niayesh Afshordi, Joao Magueijo
Summary: In this study, the researchers use the quantum unimodular theory of gravity to investigate the relationship between the cosmological constant and the energy scale for the emergence of cosmological classicality. The findings suggest that a perennially quantum Universe would occur if the cosmological constant is zero. The study also establishes a lower bound on the uncertainty of the unimodular clock or the cosmic time for the emergence of classicality based on the smallness of the cosmological constant. Classicality arises at around 7 x 1011 GeV for the observed value of the cosmological constant, highlighting the importance of understanding the classicality and quantum nature of the Universe.
Article
Astronomy & Astrophysics
Joao Magueijo
Summary: This paper examines the proposal that time and constants of nature are conjugate to each other. It is found that different constants are associated with different times. In regions dominated by a single constant, the Hamiltonian constraint can be reframed as a Schrodinger equation in the corresponding time, and the solution can be obtained by using outgoing-only monochromatic plane waves in the generalized Chern-Simons functional. The issues of unitarity and the measure employed for the inner product are also discussed.
Article
Astronomy & Astrophysics
Bruno Alexandre, Joao Magueijo
Summary: The research explores the effects of using different types of clocks simultaneously in quantum cosmology, finding that using two coherent clocks at the same time is disastrous for recovering the classical limit, leading to strong quantum effects. Semiclassical states are obtained by imposing a single clock in different ways.
Article
Astronomy & Astrophysics
Joao Magueijo
Summary: This study examines the status of the Chern-Simons state from the perspective of gravity formulation using only real connection and metric variables with a real action. It is found that the constraints are solved by a modification of the Chern-Simons state, which is a pure phase. A straightforward modification of the real Chem-Simons state is also a solution in quasitopological theories based on the Euler invariant.
Article
Astronomy & Astrophysics
Joao Magueijo, Tom Zlosnik
Summary: In the Einstein-Cartan framework, it is proposed to leave the torsion inside the constraints before quantization, leading to kinematical wave functions with respect to the torsion. The torsion-free condition can then be imposed as a condition upon the physical wave packets, allowing for quantum fluctuations in the torsion. When considering torsion, the Hartle-Hawking wave function is replaced by a Gauss-Airy function with finite norm.
Article
Astronomy & Astrophysics
Joao Magueijo, Tom Zlosnik, Simone Speziale
Article
Astronomy & Astrophysics
Stephon Alexander, Leah Jenks, Pavel Jirousek, Joao Magueijo, Tom Zlosnik
Article
Astronomy & Astrophysics
Joao Magueijo
