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Exact fermionic Chern-Simons-Kodama state in quantum gravity

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Physical Review D 2022年第10期106卷 106012-106012页

作者： Stephon Alexander Tatsuya Daniel Marcell Howard Morgane König Brown Theoretical Physics Center Department of Physics Brown University Providence 02906 RI United States Pittsburgh Particle Physics Astrophysics Cosmology Center Department of Physics and Astronomy University of Pittsburgh Pittsburgh 15260 PA United States Laboratory of Nuclear Science and Center for Theoretical Physics Massachusetts Institute of Technology Cambridge 02139 MA United States

The Chern-Simons-Kodama (CSK) state is an exact, nonperturbative wave function in the Ashtekar formulation of classical general relativity. In this work, we find a generalized fermionic CSK state by solving the extended gravitational and fermionic Hamiltonian constraints of the Wheeler-DeWitt equation exactly. We show that this new state reduces to the original Kodama state upon symmetry reduction to Friedmann-Lematre-Robertson-Walker (FLRW) coordinates with perturbative fermionic corrections, making contact with the Hartle-Hawking and Vilenkin wave functions of the universe in cosmology. We also find that when both torsion and fermions are nonvanishing, the wave function possesses a finite amplitude to evade the big bang curvature singularity.

关键词： cosmology Gauge theories Quantum gravity

Forecasts for constraining Lorentz-violating damping of gravitational waves from compact binary inspirals

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Physical Review D 2024年第10期109卷 104022-104022页

作者： Bo-Yang Zhang (张博扬) Tao Zhu (朱涛) Jing-Fei Zhang (张敬飞) Xin Zhang (张鑫) Key Laboratory of Cosmology and Astrophysics (Liaoning) and College of Sciences Northeastern University Shenyang 110819 China Institute for Theoretical Physics and Cosmology Zhejiang University of Technology Hangzhou 310032 China United Center for Gravitational Wave Physics (UCGWP) Zhejiang University of Technology Hangzhou 310032 China Key Laboratory of Data Analytics and Optimization for Smart Industry (Ministry of Education) Northeastern University Shenyang 110819 China National Frontiers Science Center for Industrial Intelligence and Systems Optimization Northeastern University Shenyang 110819 China

Violation of Lorentz symmetry can result in two distinct effects in the propagation of the gravitational waves (GWs). One is a modified dispersion relation and another is a frequency-dependent damping of GWs. While the former has been extensively studied in the literature, in this paper we concentrate on the frequency-dependent damping effect that arises from several specific Lorentz-violating theories, such as spatial covariant gravities, Hořava-Lifshitz gravities, etc. This Lorentz-violating damping effect changes the damping rate of GWs at different frequencies and leads to an amplitude correction to the GW waveform of compact binary inspiral systems. With this modified waveform, we then use the Fisher information matrix to investigate the prospects of constraining the Lorentz-violating damping effect with GW observations. We consider both ground-based and space-based GW detectors, including the advanced LIGO, Einstein Telescope, Cosmic Explorer (CE), Taiji, TianQin, and LISA. Our results indicate that the ground-based detectors in general give tighter constraints than those from the space-based detectors. Among the considered three ground-based detectors, CE can give the tightest constraints on the Lorentz-violating damping effect, which improves the current constraint from LIGO-Virgo-KAGRA events by about 8 times.

关键词： Alternative gravity theories Gravitational waves

Cosmological domain walls from the breaking of S4 flavor symmetry

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Physical Review D 2024年第5期109卷 055048-055048页

作者： Adil Jueid Mohamed Amin Loualidi Salah Nasri Mohamed Amine Ouahid Particle Theory and Cosmology Group Center for Theoretical Physics of the Universe Institute for Basic Science (IBS) 34126 Daejeon South Korea Department of physics United Arab Emirates University Al-Ain United Arab Emirates The Abdus Salam International Centre for Theoretical Physics Strada Costiera 11 I-34014 Trieste Italy LPHE-Modeling and Simulations Faculty of Science Mohammed V University in Rabat Morocco and Centre of Physics and Mathematics Morocco

In this work, we delve into the often overlooked cosmological implications of the spontaneous breaking of the non-Abelian discrete groups, specifically focusing on the formation of domain walls in the case of S4 flavor symmetry. In particular, we investigate three interesting breaking patterns of the S4 group and study the structure of the domain walls in the broken phase for three possible residual symmetries. The presentation of domain walls in the case of multiple vacua is usually complicated, which therefore implies that most of the analyses only approximate their presentation. Here, we propose a subtle way to represent the S4 domain wall networks by presenting the vacua in each breaking pattern as vectors with their components corresponding to their coordinates in the flavon space. Then, through the properties of the obtained vectors, we find that the domain wall networks can be represented by Platonic or Archimedean solids where the vertices represent the degenerate vacua while the edges correspond to the domain walls that separate them. As an illustration, we propose a type-II seesaw model that is based on the S4 flavor symmetry, and study its phenomenological implications on the neutrino sector. To solve the domain wall problem within this toy model, we consider an approach based on high-dimensional effective operators induced by gravity that explicitly break the structure of the induced vacua favoring one vacuum over the others.

关键词： Cosmic strings & domain walls cosmology Extensions of scalar sector Spontaneous symmetry breaking Hypothetical scalars Neutrinos Flavor symmetries

Electron as a Tiny Mirror: Radiation From a Worldline With Asymptotic Inertia

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arXiv 2023年

作者： Good, Michael R.R. Ong, Yen Chin Department of Physics Energetic Cosmos Laboratory Nazarbaev University Astana010000 Kazakhstan Leung Center for Cosmology & Particle Astrophysics National Taiwan University Taipei10617 Taiwan Center for Gravitation and Cosmology College of Physical Science and Technology Yangzhou University Yangzhou225002 China Shanghai Frontier Science Center for Gravitational Wave Detection School of Aeronautics and Astronautics Shanghai Jiao Tong University Shanghai200240 China

We present a moving mirror analog of the electron, whose worldline possesses asymptotic constant velocity with corresponding beta Bogolubov coefficients that are consistent with finite total emitted energy. Furthermore, the quantum analog model is in agreement with the total energy obtained by integrating the classical Larmor power. © 2023, CC BY.

关键词： Mirrors

Beyond Coleman’s Instantons

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arXiv 2024年

作者： Sasaki, Misao Yingcharoenrat, Vicharit Zhang, Ying-Li School of Physics Science and Engineering Tongji University Shanghai200092 China Institute for Advanced Study of Tongji University Shanghai200092 China UTIAS The University of Tokyo Chiba277-8583 Japan Center for Gravitational Physics and Quantum Information Yukawa Institute for Theoretical Physics Kyoto University Kyoto606-8502 Japan Leung Center for Cosmology and Particle Astrophysics National Taiwan University Taipei10617 Taiwan High Energy Physics Research Unit Department of Physics Faculty of Science Chulalongkorn University Pathumwan Bangkok10330 Thailand Institute of Theoretical Physics Chinese Academy of Sciences Beijing100190 China Center for Gravitation and Cosmology Yangzhou University Yangzhou225009 China

In the absence of gravity, Coleman’s theorem states that the O(4)-symmetric instanton solution, which is regular at the origin and exponentially decays at infinity, gives the lowest action. Perturbatively, this implies that any small deformation from O(4)-symmetry gives a larger action. In this letter we investigate the possibility of extending this theorem to the situation where the O(4)-symmetric instanton is singular, provided that the action is finite. In particular, we show a general form of the potential around the origin, which realizes a singular instanton with finite action. We then discuss a concrete example in which this situation is realized, and analyze non-trivial anisotropic deformations around the solution perturbatively. Intriguingly, in contrast to the case of Coleman’s instantons, we find that there exists a deformed solution that has the same action as the one for the O(4)-symmetric solution up to the second order in perturbation. Our result implies that there exist non-O(4)-symmetric solutions with finite action beyond Coleman’s instantons, and gives rise to the possibility of the existence of a non-O(4)-symmetric instanton with a lower action. © 2024, CC BY.

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Reconstructing the Thermal Sunyaev Zeldovich Power Spectrum from Planck using the ABS Method

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arXiv 2024年

作者： Zhang, Zhaoxuan Zhang, Le Zhang, Pengjie Zhang, Jun School of Physics and Astronomy Sun Yat-Sen University Zhuhai519082 China Peng Cheng Laboratory Guangdong Shenzhen518066 China CSST Science Center for the Guangdong-Hongkong-Macau Greater Bay Area SYSU Zhuhai519082 China Shanghai Jiao Tong University China Tsung-Dao Lee Institute Shanghai Jiao Tong University Shanghai200240 China Key Laboratory for Particle Astrophysics and Cosmology MOE Shanghai Key Laboratory for Particle Physics and Cosmology China

This study employs a novel approach for reconstructing the thermal Sunyaev-Zeldovich (tSZ) effect power spectrum from Planck data using the Analytical Blind Separation (ABS) method. The ABS method improves the recovery of weak signals, by applying eigenmode exclusion for low signal-to-noise ratio regimes and introducing a shift parameter to stabilize calculations. Validation through simulated Planck data demonstrates the robustness of ABS in reconstructing the tSZ power spectrum, even under challenging conditions. In the analysis of the Planck PR3 full-mission data, ABS shows lower amplitudes at 300 compared to the Planck 2015 band powers using the MILCA and NILC foreground cleaning methods. After marginalizing over residual foreground components, the ABS analysis finds the overall tSZ power spectrum amplitude to be 20% lower than the Planck best-fit one, suggesting a smaller S8. At 200, the tSZ band power is 1012( + 1)Cyy/(2π) = 0.126 ± 0.018, largely independent of the tSZ model choice. These findings highlight the potential of the ABS method as a promising alternative for tSZ power spectrum analysis, offering a robust and independent means of extracting cosmological parameters. Copyright © 2024, The Authors. All rights reserved.

关键词： Signal to noise ratio

An SZ-Like Effect on Cosmological Gravitational Wave Backgrounds

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arXiv 2023年

作者： Daniel, Tatsuya Howard, Marcell König, Morgane Brown Theoretical Physics Center Department of Physics Brown University ProvidenceRI02912 United States Pittsburgh Particle Physics Astrophysics and Cosmology Center Department of Physics and Astronomy University of Pittsburgh PittsburghPA15260 United States Department of Physics and Astronomy Dartmouth College HanoverNH03755 United States Laboratory of Nuclear Science Center for Theoretical Physics Massachusetts Institute of Technology CambridgeMA02139 United States

Cosmological gravitational wave backgrounds (CGWBs) are the conglomeration of unresolved gravitational wave signals from early Universe sources, which make them a promising tool for cosmologists. Because gravitons decouple from the cosmic plasma early on, one can consider interactions between gravitons and any particle species that were present in the very early Universe. We show that analogous to the cosmic microwave background, elastic scattering on any cosmological background will induce small distortions in its energy density spectrum. We then quantify the magnitude of these spin-dependent spectral distortions when attributed to the dark matter in the early Universe. Lastly, we give estimates for potentially measurable distortions on CGWBs due to gravitational scattering by primordial black holes. Copyright © 2023, The Authors. All rights reserved.

关键词： Gravity waves

Dynamics of Bronnikov-Ellis wormhole with double-null simulation

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arXiv 2025年

作者： Xu, Anyuan Chew, Xiao Yan Yeom, Dong-Han School of Science Jiangsu University of Science and Technology Zhenjiang212100 China Department of Physics Education Pusan National University Busan46241 Korea Republic of Research Center for Dielectric and Advanced Matter Physics Pusan National University Busan46241 Korea Republic of Leung Center for Cosmology and Particle Astrophysics National Taiwan University Taipei10617 Taiwan Department of Physics and Astronomy University of Waterloo WaterlooONN2L 3G1 Canada

We investigate the dynamical collapse of Bronnikov-Ellis (BE) wormhole using the double-null formalism, where its throat is characterized by the coincidence of two curves r,u = 0 and r,v = 0. The emission of two ingoing pulses: normal scalar and phantom fields in the wormhole spacetime reveals two distinct instability scenarios: a normal scalar field triggers gravitational collapse into a black hole where the singularity r = 0 hidden by the event horizon (r,u = 0 and r,v = 0);while a phantom field drives inflationary expansion of wormhole, decoupling two asymptotic regions with the cosmological horizon (r,u = 0 and r,v = 0). The process of two scenarios can be accelerated by increasing the amplitude of pulses but can be delayed by increasing the wormhole’s mass. Additionally, the collisions of two identical pulses from ingoing and outgoing null directions in the massless BE wormhole fail to cure the instabilities because the two scenarios can still occur, but the formation of a black hole can be delayed for the collision of normal and phantom fields. Interestingly, the strategic tuning of emission timing for outgoing phantom field to collide with ingoing normal scalar field can temporarily stabilize the wormhole throat by restoring the coincidence of r,u and r,v again after their separation. This offers us valuable insights into extending the lifetime of a traversable wormhole. © 2025, CC BY.

关键词： Black holes

NANOGrav results and dark first order phase transitions

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science China(physics,Mechanics & Astronomy) 2021年第9期64卷 9-14页

作者： Andrea Addazi Yi-Fu Cai Qingyu Gan Antonino Marciano Kaiqiang Zeng Center for Theoretical Physics College of PhysicsSichuan UniversityChengdu 610065China Istituto Nazionale di Fisica Nucleare sezione Roma Tor VergataRome I-00133Italy Department of Astronomy School of Physical SciencesUniversity of Science and Technology of ChinaHefei 230026China Chinese Academy of Sciences Key Laboratory for Researches in Galaxies and CosmologyUniversity of Science and Technology of ChinaHefei 230026China School of Astronomy and Space Science University of Science and Technology of ChinaHefei 230026China Department of Physics&Center for Field Theory and Particle Physics Fudan UniversityShanghai 200433China Laboratori Nazionali di Frascati Istituto Nazionale di Fisica Nucleare Via Enrico Fermi 54Frascati(Roma)I-00044Italy

The recent NANOGrav evidence of a common-source stochastic background provides a hint to gravitational waves(GW)radiation from the Early *** show that this result can be interpreted as a GW spectrum produced from first order phase transitions(FOPTs)around a temperature in the keV-MeV *** a class of FOPTs at temperatures much below the electroweak scale can be naturally envisaged in several warm dark matter models such as Majoron dark matter.

关键词： gravitational waves first order phase transitions warm dark matter effective field theory