Pub Date : 2024-04-05DOI: 10.1088/1361-6382/ad3b5e
E. Gasperín, Francisco Pais
This note gives a concise derivation of a twistor-initial-data characterisation of pp-wave spacetimes in vacuum. The construction is based on a similar calculation for the Minkowski spacetime in [Class. Quantum Grav. 28 075010]. The key difference is that for the Minkowski spacetime a necessary condition is that $nabla_{A}{}^{A'}bar{kappa}_{A'} neq 0$. In this note it is shown that if $nabla_{A}{}^{A'}bar{kappa}_{A'}=0$ then the development is a pp-wave spacetime. Furthermore, it is shown that such condition propagates off the initial hypersurface, which, in turn, gives a emph{twistor initial data characterisation of pp-waves}.
本论文简明地推导了真空中pp波时空的扭子初始数据特征。其构造基于[Class. Quantum Grav.］关键区别在于，对于闵科夫斯基时空，一个必要条件是 $nabla_{A}{}^{A'}bar{kappa}_{A'} 。neq 0$.在本论文中，我们将证明如果 $nabla_{A}{}^{A'}bar{kappa}_{A'}=0$ 那么发展的是一个 pp 波时空。此外，我们还证明了这样的条件会从初始超表面传播出去，这反过来又给出了pp波的emph{twistor initial data characterisation of pp-waves}。
{"title":"Twistor initial data characterisation of pp-waves","authors":"E. Gasperín, Francisco Pais","doi":"10.1088/1361-6382/ad3b5e","DOIUrl":"https://doi.org/10.1088/1361-6382/ad3b5e","url":null,"abstract":"\u0000 This note gives a concise derivation of a twistor-initial-data characterisation of pp-wave spacetimes in vacuum. The construction is based on a similar calculation for the Minkowski spacetime in [Class. Quantum Grav. 28 075010]. The key difference is that for the Minkowski spacetime a necessary condition is that $nabla_{A}{}^{A'}bar{kappa}_{A'} neq 0$. In this note it is shown that if $nabla_{A}{}^{A'}bar{kappa}_{A'}=0$ then the development is a pp-wave spacetime. Furthermore, it is shown that such condition propagates off the initial hypersurface, which, in turn, gives a emph{twistor initial data characterisation of pp-waves}.","PeriodicalId":505126,"journal":{"name":"Classical and Quantum Gravity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140735756","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-05DOI: 10.1088/1361-6382/ad3b5f
S. Maurya, Abdelghani Errehymy, G. Vîlcu, H. Alrebdi, K. S. Nisar, A. Abdel‐Aty
In this paper, a significant leap forward in understanding compact stellar systems and the modified $f(Q)$ gravity theory is achieved. The pivotal discovery lies in the successful derivation of an exact solution that fulfills the static geometry and spherical symmetry criteria, permitting the studying of compact stellar configurations with an anisotropic fluid. The model is rigorously tested and satisfies the vital physical conditions within the stellar fluid, guaranteeing its viability. The equi-mass contours highlight an impressive correlation between the $f(Q)$ gravity parameters. Boosting $alpha$ while keeping $beta$ fixed and concurrently boosting $R$ leads to a significant global boost in mass distribution. This can be ascribed to the enhanced coupling arising from a higher $alpha$, which broadens the mass distribution. In addition, the larger object size arising from the rise in $R$ allows for more mass accommodation. Therefore, raising both $R$ and $alpha$ leads to an exaggerated mass distribution, proving the combined influence of coupling strength and object size on total mass. Altogether, this investigation advances our knowledge of compact stellar systems and supports the evolution of the modified $f(Q)$ theory of gravity, opening the way for more breakthroughs in this field.
{"title":"Anisotropic compact star in linear f(Q)-action","authors":"S. Maurya, Abdelghani Errehymy, G. Vîlcu, H. Alrebdi, K. S. Nisar, A. Abdel‐Aty","doi":"10.1088/1361-6382/ad3b5f","DOIUrl":"https://doi.org/10.1088/1361-6382/ad3b5f","url":null,"abstract":"\u0000 In this paper, a significant leap forward in understanding compact stellar systems and the modified $f(Q)$ gravity theory is achieved. The pivotal discovery lies in the successful derivation of an exact solution that fulfills the static geometry and spherical symmetry criteria, permitting the studying of compact stellar configurations with an anisotropic fluid. The model is rigorously tested and satisfies the vital physical conditions within the stellar fluid, guaranteeing its viability. The equi-mass contours highlight an impressive correlation between the $f(Q)$ gravity parameters. Boosting $alpha$ while keeping $beta$ fixed and concurrently boosting $R$ leads to a significant global boost in mass distribution. This can be ascribed to the enhanced coupling arising from a higher $alpha$, which broadens the mass distribution. In addition, the larger object size arising from the rise in $R$ allows for more mass accommodation. Therefore, raising both $R$ and $alpha$ leads to an exaggerated mass distribution, proving the combined influence of coupling strength and object size on total mass. Altogether, this investigation advances our knowledge of compact stellar systems and supports the evolution of the modified $f(Q)$ theory of gravity, opening the way for more breakthroughs in this field.","PeriodicalId":505126,"journal":{"name":"Classical and Quantum Gravity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140736163","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-04DOI: 10.1088/1361-6382/ad3ac8
Hao-Sheng Zeng, Heng Liu, Lian-Jie Wu
We study the Schwinger correlation of Dirac fields in the noninertial frames under the influences of both constant and pulsed electric fields. We use both the entanglement negativity and quantum mutual information between particle and antiparticle as the indicator of the Schwinger correlation observed by the accelerated observers. We find that the Schwinger correlation in the inertial frames is the largest. With the increase of acceleration of the observers, the Schwinger correlation becomes smaller and smaller, but does not vanish in the limit of infinite acceleration. For the given acceleration, the Schwinger correlation is a nonmonotonic function of the electric field intensity, and there is an optimal value of electric field intensity for which the Schwinger correlation is the largest. In the case of pulsed electric fields, the Schwinger correlation is also the nonmonotonic function of pulsed width, which suggests the existence of optimal pulsed width for observing Schwinger correlation.
{"title":"Schwinger correlation of Dirac fields in accelerated frames","authors":"Hao-Sheng Zeng, Heng Liu, Lian-Jie Wu","doi":"10.1088/1361-6382/ad3ac8","DOIUrl":"https://doi.org/10.1088/1361-6382/ad3ac8","url":null,"abstract":"\u0000 We study the Schwinger correlation of Dirac fields in the noninertial frames under the influences of both constant and pulsed electric fields. We use both the entanglement negativity and quantum mutual information between particle and antiparticle as the indicator of the Schwinger correlation observed by the accelerated observers. We find that the Schwinger correlation in the inertial frames is the largest. With the increase of acceleration of the observers, the Schwinger correlation becomes smaller and smaller, but does not vanish in the limit of infinite acceleration. For the given acceleration, the Schwinger correlation is a nonmonotonic function of the electric field intensity, and there is an optimal value of electric field intensity for which the Schwinger correlation is the largest. In the case of pulsed electric fields, the Schwinger correlation is also the nonmonotonic function of pulsed width, which suggests the existence of optimal pulsed width for observing Schwinger correlation.","PeriodicalId":505126,"journal":{"name":"Classical and Quantum Gravity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140745476","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-28DOI: 10.1088/1361-6382/ad38fb
Xiao-Jun Yue, Zhoujian Cao
An intermediate mass black hole (IMBH) may have a dark matter (DM) minihalo around it and develop a spiky structure called DM minispike. Gravitational waves (GWs) can be produced if a stellar compact object, such as a black hole (BH) or neutron star, inspirals into the IMBH. This kind of systems are known as itermediate-mass-ratio-inspirals (IMRIs) and may be observed by space-based gravitational wave detectors including LISA, Taiji and Tianqin. In this paper, we lay the foundations for the construction of analytic expressions for Fourier-domain gravitational waves produced by eccentric IMRIs with DM minispikes in a post-circular or small-eccentricity approximation (e < 0.4). We take the effect of dynamical friction from the DM as a perturbation, and decompose the dynamical equations into perturbed part and unperturbed part. The equations are solved in a series expansion form about zero initial eccentricity to eighth order. The time-dependent, “plus” and “cross” polarizations are expanded in Bessel functions, which are then self-consistently reexpanded in a power series about zero initial eccentricity. The stationary-phase approximation is then employed to obtain the explicit DM-modified analytic expressions for the Fourier transform of the post-circular expanded, time-domain signal. We exemplify this framework by considering a typical IMRI with a DM minispike and find the GW detectability strongly depends on the radial profile of the DM distribution. When the density of DM is large enough, the signal to noise ratio (SNR) will be degraded significantly and a detection loss may occur if we use a template without the effect of DM to treat a signal including the DM effect. With the Fourier-domain gravitational waveforms we also estimate the accuracy of the measurement of the DM minispike parameters in our reference model. Our framework hold the promise to construct a “ready-to-use” Fourier-domain waveforms for data analysis of eccentric IMRIs with DM minispikes.
{"title":"Gravitational waves with dark matter minispikes: Fourier-domain waveforms of eccentric intermediate-mass-ratio-inspirals","authors":"Xiao-Jun Yue, Zhoujian Cao","doi":"10.1088/1361-6382/ad38fb","DOIUrl":"https://doi.org/10.1088/1361-6382/ad38fb","url":null,"abstract":"\u0000 An intermediate mass black hole (IMBH) may have a dark matter (DM) minihalo around it and develop a spiky structure called DM minispike. Gravitational waves (GWs) can be produced if a stellar compact object, such as a black hole (BH) or neutron star, inspirals into the IMBH. This kind of systems are known as itermediate-mass-ratio-inspirals (IMRIs) and may be observed by space-based gravitational wave detectors including LISA, Taiji and Tianqin. In this paper, we lay the foundations for the construction of analytic expressions for Fourier-domain gravitational waves produced by eccentric IMRIs with DM minispikes in a post-circular or small-eccentricity approximation (e < 0.4). We take the effect of dynamical friction from the DM as a perturbation, and decompose the dynamical equations into perturbed part and unperturbed part. The equations are solved in a series expansion form about zero initial eccentricity to eighth order. The time-dependent, “plus” and “cross” polarizations are expanded in Bessel functions, which are then self-consistently reexpanded in a power series about zero initial eccentricity. The stationary-phase approximation is then employed to obtain the explicit DM-modified analytic expressions for the Fourier transform of the post-circular expanded, time-domain signal. We exemplify this framework by considering a typical IMRI with a DM minispike and find the GW detectability strongly depends on the radial profile of the DM distribution. When the density of DM is large enough, the signal to noise ratio (SNR) will be degraded significantly and a detection loss may occur if we use a template without the effect of DM to treat a signal including the DM effect. With the Fourier-domain gravitational waveforms we also estimate the accuracy of the measurement of the DM minispike parameters in our reference model. Our framework hold the promise to construct a “ready-to-use” Fourier-domain waveforms for data analysis of eccentric IMRIs with DM minispikes.","PeriodicalId":505126,"journal":{"name":"Classical and Quantum Gravity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140368845","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-27DOI: 10.1088/1361-6382/ad387c
Xin-Lei Zhao, Panpan Wang, Cheng-Gang Shao
The Laser Interferometer Space Antenna (LISA) uses laser interferometry to measure gravitational wave-induced distance changes between freely falling test masses on separate spacecraft. In practice, the space-borne gravitational wave detector operates in a plasma medium, and subsequently, the variations in electron density affect the refractive index and add displacement noise to measurements. Geometric time-delay interferometry (TDI) is the TDI combinations searched by geometric method, which is employed to mitigate overwhelming laser phase noise. This study explores all forty-five second-generation geometric TDI combinations up to sixteen links, analyzing plasma noise effects via power spectral density (PSD) and cross-spectral density (CSD) calculations for different optical links. Our findings reveal that plasma noise can exceed the noise floor, which comprises optical metrology system (OMS) and test mass (TM) acceleration noise, in certain low-frequency regions due to different noise transfer behaviors. Further, we establish electron density requirements for various TDI combinations, showing that densities below $100~text{cm}^{-3}/sqrt{text{Hz}}~@~10~text{mHz}$ satisfy LISA's criteria across all forty-five combinations. This allows for optimized TDI selection based on specific plasma densities.
{"title":"The evaluation for plasma noise in arbitrary time-delay interferometry combinations","authors":"Xin-Lei Zhao, Panpan Wang, Cheng-Gang Shao","doi":"10.1088/1361-6382/ad387c","DOIUrl":"https://doi.org/10.1088/1361-6382/ad387c","url":null,"abstract":"\u0000 The Laser Interferometer Space Antenna (LISA) uses laser interferometry to measure gravitational wave-induced distance changes between freely falling test masses on separate spacecraft. In practice, the space-borne gravitational wave detector operates in a plasma medium, and subsequently, the variations in electron density affect the refractive index and add displacement noise to measurements. Geometric time-delay interferometry (TDI) is the TDI combinations searched by geometric method, which is employed to mitigate overwhelming laser phase noise. This study explores all forty-five second-generation geometric TDI combinations up to sixteen links, analyzing plasma noise effects via power spectral density (PSD) and cross-spectral density (CSD) calculations for different optical links. Our findings reveal that plasma noise can exceed the noise floor, which comprises optical metrology system (OMS) and test mass (TM) acceleration noise, in certain low-frequency regions due to different noise transfer behaviors. Further, we establish electron density requirements for various TDI combinations, showing that densities below $100~text{cm}^{-3}/sqrt{text{Hz}}~@~10~text{mHz}$ satisfy LISA's criteria across all forty-five combinations. This allows for optimized TDI selection based on specific plasma densities.","PeriodicalId":505126,"journal":{"name":"Classical and Quantum Gravity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140376266","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-21DOI: 10.1088/1361-6382/ad36a8
M. Bojowald, Erick Ivan Duque Gonzalez
A complete canonical formulation of general covariance makes it possible to construct new modified theories of gravity that are not of higher-curvature form, as shown here in a spherically symmetric setting. The usual uniqueness theorems are evaded by using a crucial and novel ingredient, allowing for fundamental fields of gravity distinct from an emergent space-time metric that provides a geometrical structure to all solutions. As specific examples, there are new expansion-shear couplings in cosmological models, a form of modified Newtonian dynamics (MOND) can appear in a space-time covariant theory without introducing extra fields, and related effects help to make effective models of canonical quantum gravity fully consistent with general covariance.
{"title":"Emergent modified gravity","authors":"M. Bojowald, Erick Ivan Duque Gonzalez","doi":"10.1088/1361-6382/ad36a8","DOIUrl":"https://doi.org/10.1088/1361-6382/ad36a8","url":null,"abstract":"\u0000 A complete canonical formulation of general covariance makes it possible to construct new modified theories of gravity that are not of higher-curvature form, as shown here in a spherically symmetric setting. The usual uniqueness theorems are evaded by using a crucial and novel ingredient, allowing for fundamental fields of gravity distinct from an emergent space-time metric that provides a geometrical structure to all solutions. As specific examples, there are new expansion-shear couplings in cosmological models, a form of modified Newtonian dynamics (MOND) can appear in a space-time covariant theory without introducing extra fields, and related effects help to make effective models of canonical quantum gravity fully consistent with general covariance.","PeriodicalId":505126,"journal":{"name":"Classical and Quantum Gravity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140221399","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-19DOI: 10.1088/1361-6382/ad3081
Jos'e Navarro-Salas
Cosmic censorship protects the outside world from black hole singularities and paves the way for assigning entropy to gravity at the event horizons. We point out a tension between cosmic censorship and the quantum backreacted geometry of Schwarzschild black holes, induced by vacuum polarization and driven by the conformal anomaly. A similar tension appears for the Weyl curvature hypothesis at the Big Bang singularity. We argue that the requirement of exact conformal symmetry resolves both conflicts and has major implications for constraining the set of fundamental constituents of the Standard Model.
{"title":"Black holes, conformal symmetry, and fundamental fields","authors":"Jos'e Navarro-Salas","doi":"10.1088/1361-6382/ad3081","DOIUrl":"https://doi.org/10.1088/1361-6382/ad3081","url":null,"abstract":"\u0000 Cosmic censorship protects the outside world from black hole singularities and paves the way for assigning entropy to gravity at the event horizons. We point out a tension between cosmic censorship and the quantum backreacted geometry of Schwarzschild black holes, induced by vacuum polarization and driven by the conformal anomaly. A similar tension appears for the Weyl curvature hypothesis at the Big Bang singularity. We argue that the requirement of exact conformal symmetry resolves both conflicts and has major implications for constraining the set of fundamental constituents of the Standard Model.","PeriodicalId":505126,"journal":{"name":"Classical and Quantum Gravity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140230006","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-19DOI: 10.1088/1361-6382/ad35a1
Gavin Wallace, M. Ben Yaala, simon tait, G. Vajente, Thomas McCanny, Caspar Clark, Des Gibson, J. Hough, Iain W Martin, Sheila Rowan, S. Reid
Silicon nitride thin films were deposited at room temperature employing a custom ion beam deposition (IBD) system. The stoichiometry of these films was tuned by controlling the nitrogen gas flow through the ion source and a process gas ring. A correlation is established between the process parameters, such as ion beam voltage and ion current, and the optical and mechanical properties of the films based on post-deposition heat treatment. The results show that with increasing heat treatment temperature, the mechanical loss of these materials as well as their optical absorption decreases producing films with an extinction coefficient as low as k = 6.2(±0.5)×10−7 at 1064nm for samples annealed at 900○C. This presents the lowest value for IBD SiNx within the context of gravitational wave detector applications. The mechanical loss of the films was measured to be ϕ = 2.1(±0.6) × 10−4 once annealed post deposition to 900○C.
{"title":"Non-stoichiometric Silicon Nitride for Future Gravitational Wave Detectors","authors":"Gavin Wallace, M. Ben Yaala, simon tait, G. Vajente, Thomas McCanny, Caspar Clark, Des Gibson, J. Hough, Iain W Martin, Sheila Rowan, S. Reid","doi":"10.1088/1361-6382/ad35a1","DOIUrl":"https://doi.org/10.1088/1361-6382/ad35a1","url":null,"abstract":"\u0000 Silicon nitride thin films were deposited at room temperature employing a custom ion beam deposition (IBD) system. The stoichiometry of these films was tuned by controlling the nitrogen gas flow through the ion source and a process gas ring. A correlation is established between the process parameters, such as ion beam voltage and ion current, and the optical and mechanical properties of the films based on post-deposition heat treatment. The results show that with increasing heat treatment temperature, the mechanical loss of these materials as well as their optical absorption decreases producing films with an extinction coefficient as low as k = 6.2(±0.5)×10−7 at 1064nm for samples annealed at 900○C. This presents the lowest value for IBD SiNx within the context of gravitational wave detector applications. The mechanical loss of the films was measured to be ϕ = 2.1(±0.6) × 10−4 once annealed post deposition to 900○C.","PeriodicalId":505126,"journal":{"name":"Classical and Quantum Gravity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140228364","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-14DOI: 10.1088/1361-6382/ad33cd
V. K. Oikonomou
In this work we consider an axionic scalar-tensor theory of gravity and its effects on static neutron stars. The axionic theory is considered in the regime in which the axion oscillates around its potential minimum, which cosmologically occurs post-inflationary, when the Hubble rate is of the same order as the axion mass. We construct the TOV equations for this axionic theory and for a spherically symmetric static spacetime and we solve these numerically using a quite robust double shooting LSODA based python integration method. Regarding the equations of state, we used nine mainstream and quite popular ones, namely, the WFF1, the SLy, the APR, the MS1, the AP3, the AP4, the ENG, the MPA1 and the MS1b, using the piecewise polytropic description for each. From the extracted data we calculate the Jordan frame masses and radii, and we confront the resulting phenomenology with five well-known neutron star constraints. As we demonstrate, the AP3, the ENG and the MPA1 equations of state yield phenomenologically viable results which are compatible with the constraints, with the MPA1 equation of state enjoying an elevated role among the three. The reason is that the MPA1 fits well the phenomenological constraints. A mentionable feature is the fact that all the viable phenomenologically equations of state produce maximum masses which are in the mass-gap region with Mmax > 2.5Mfi , but lower that the causal 3 solar masses limit. We also compare the neutron star phenomenology produced by the axionic scalar-tensor theory with the phenomenology produced by inflationary attractors scalar-tensor theories.
{"title":"Phenomenology of axionic static neutron stars with masses in the mass-gap region","authors":"V. K. Oikonomou","doi":"10.1088/1361-6382/ad33cd","DOIUrl":"https://doi.org/10.1088/1361-6382/ad33cd","url":null,"abstract":"\u0000 In this work we consider an axionic scalar-tensor theory of gravity and its effects on static neutron stars. The axionic theory is considered in the regime in which the axion oscillates around its potential minimum, which cosmologically occurs post-inflationary, when the Hubble rate is of the same order as the axion mass. We construct the TOV equations for this axionic theory and for a spherically symmetric static spacetime and we solve these numerically using a quite robust double shooting LSODA based python integration method. Regarding the equations of state, we used nine mainstream and quite popular ones, namely, the WFF1, the SLy, the APR, the MS1, the AP3, the AP4, the ENG, the MPA1 and the MS1b, using the piecewise polytropic description for each. From the extracted data we calculate the Jordan frame masses and radii, and we confront the resulting phenomenology with five well-known neutron star constraints. As we demonstrate, the AP3, the ENG and the MPA1 equations of state yield phenomenologically viable results which are compatible with the constraints, with the MPA1 equation of state enjoying an elevated role among the three. The reason is that the MPA1 fits well the phenomenological constraints. A mentionable feature is the fact that all the viable phenomenologically equations of state produce maximum masses which are in the mass-gap region with Mmax > 2.5Mfi , but lower that the causal 3 solar masses limit. We also compare the neutron star phenomenology produced by the axionic scalar-tensor theory with the phenomenology produced by inflationary attractors scalar-tensor theories.","PeriodicalId":505126,"journal":{"name":"Classical and Quantum Gravity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140243131","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-12DOI: 10.1088/1361-6382/ad32df
P. Gregori, R. Schiappa
Two remarkable facts about Jackiw-Teitelboim two-dimensional dilaton-gravity have been recently uncovered: this theory is dual to an ensemble of quantum mechanical theories; and such ensembles are described by a random matrix model which itself may be regarded as a special (large matter-central-charge) limit of minimal string theory. This work addresses this limit, putting it in its broader matrix-model context; comparing results between multicritical models and minimal strings (i.e., changing in-between multicritical and conformal backgrounds); and in both cases making the limit of large matter-central-charge precise (as such limit can also be defined for the multicritical series). These analyses are first done via spectral geometry, at both perturbative and nonperturbative levels, addressing the resurgent large-order growth of perturbation theory, alongside a calculation of nonperturbative instanton-actions and corresponding Stokes data. This calculation requires an algorithm to reach large-order, which is valid for arbitrary two-dimensional topological gravity. String equations---as derived from the Gel'fand-Dikii construction of the resolvent---are analyzed in both multicritical and minimal string theoretic contexts, and studied both perturbatively and nonperturbatively (always matching against the earlier spectral-geometry computations). The resulting solutions, as described by resurgent transseries, are shown to be resonant. The large matter-central-charge limit is addressed---in the string-equation context---and, in particular, the string equation for Jackiw-Teitelboim gravity is obtained to next derivative-orders, beyond the known genus-zero case (its possible exact-form is also discussed). Finally, a discussion of gravitational perturbations to Schwarzschild-like black hole solutions in these minimal-string models, regarded as deformations of Jackiw-Teitelboim gravity, is included---alongside a brief discussion of quasinormal modes.
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