Pub Date : 2025-11-25DOI: 10.1016/j.aop.2025.170304
Himanshu Badhani , C.M. Chandrashekar
Evolutions under non-Hermitian Hamiltonians with unbroken symmetry can be considered unitary under appropriate choices of inner products, facilitated by the so-called metric operator. While it is understood that the choice of the metric operator has no bearing on the description of the system, in this work, we show that this choice does dictate the entanglement structure of the system. We show that the partial trace of the Hermitized density matrix gives the correct representation of the reduced subsystem, and based on such operations, we elucidate the metric dependency of the reduced dynamics and consequently the observable dependence of the subsystem decomposition. We use a non-Hermitian -symmetric quantum walk as a toy model to study this metric dependency, where we use the internal (coin state) as the subsystem of interest and study the coin-position entanglement and non-Markovianity of the coin dynamics.
{"title":"Reduced dynamics in quasi-Hermitian systems","authors":"Himanshu Badhani , C.M. Chandrashekar","doi":"10.1016/j.aop.2025.170304","DOIUrl":"10.1016/j.aop.2025.170304","url":null,"abstract":"<div><div>Evolutions under non-Hermitian Hamiltonians with unbroken <span><math><mrow><mi>P</mi><mi>T</mi></mrow></math></span> symmetry can be considered unitary under appropriate choices of inner products, facilitated by the so-called metric operator. While it is understood that the choice of the metric operator has no bearing on the description of the system, in this work, we show that this choice does dictate the entanglement structure of the system. We show that the partial trace of the Hermitized density matrix gives the correct representation of the reduced subsystem, and based on such operations, we elucidate the metric dependency of the reduced dynamics and consequently the observable dependence of the subsystem decomposition. We use a non-Hermitian <span><math><mi>PT</mi></math></span>-symmetric quantum walk as a toy model to study this metric dependency, where we use the internal (coin state) as the subsystem of interest and study the coin-position entanglement and non-Markovianity of the coin dynamics.</div></div>","PeriodicalId":8249,"journal":{"name":"Annals of Physics","volume":"484 ","pages":"Article 170304"},"PeriodicalIF":3.0,"publicationDate":"2025-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145621591","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-25DOI: 10.1016/j.aop.2025.170305
Sara Giordano , Miguel A. Martin-Delgado
Testing graph completeness is a critical problem in computer science and network theory. Leveraging quantum computation, we present an efficient algorithm using the Szegedy quantum walk and quantum phase estimation (QPE). Our algorithm, which takes the number of nodes and the adjacency matrix as input, constructs a quantum walk operator and applies QPE to estimate its eigenvalues. These eigenvalues reveal the graph’s structural properties, enabling us to determine its completeness. We establish a relationship between the number of nodes in a complete graph and the number of marked nodes, optimizing the success probability and running time. The time complexity of our algorithm is , where is the number of nodes of the graph. offering a clear quantum advantage over classical methods. This approach is useful in network structure analysis, evaluating classical routing algorithms, and assessing systems based on pairwise comparisons.
{"title":"Quantum algorithm for testing graph completeness","authors":"Sara Giordano , Miguel A. Martin-Delgado","doi":"10.1016/j.aop.2025.170305","DOIUrl":"10.1016/j.aop.2025.170305","url":null,"abstract":"<div><div>Testing graph completeness is a critical problem in computer science and network theory. Leveraging quantum computation, we present an efficient algorithm using the Szegedy quantum walk and quantum phase estimation (QPE). Our algorithm, which takes the number of nodes and the adjacency matrix as input, constructs a quantum walk operator and applies QPE to estimate its eigenvalues. These eigenvalues reveal the graph’s structural properties, enabling us to determine its completeness. We establish a relationship between the number of nodes in a complete graph and the number of marked nodes, optimizing the success probability and running time. The time complexity of our algorithm is <span><math><mrow><mi>O</mi><mrow><mo>(</mo><msup><mrow><mo>log</mo></mrow><mrow><mn>2</mn></mrow></msup><mi>n</mi><mo>)</mo></mrow></mrow></math></span>, where <span><math><mi>n</mi></math></span> is the number of nodes of the graph. offering a clear quantum advantage over classical methods. This approach is useful in network structure analysis, evaluating classical routing algorithms, and assessing systems based on pairwise comparisons.</div></div>","PeriodicalId":8249,"journal":{"name":"Annals of Physics","volume":"484 ","pages":"Article 170305"},"PeriodicalIF":3.0,"publicationDate":"2025-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145621638","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-24DOI: 10.1016/j.aop.2025.170298
Duttatreya , Ipsika Mohanty , Sanjib Dey
Quantum computing’s potential for exponential speedup is fundamentally limited by decoherence, a phenomenon arising from environmental interactions. Non-Hermitian quantum mechanics, particularly -symmetric systems, offers a novel framework for extending coherence times. This study examines a qubit’s coherence under non-Hermitian -symmetric dynamics, highlighting significantly enhanced coherence times compared to Hermitian setups. The effect is especially pronounced when both the system and environment exhibit -symmetry. Interestingly, greater environmental non-Hermiticity correlates with extended coherence, contrary to traditional expectations. These findings point to promising strategies for managing decoherence, which could significantly advance approaches to quantum information processing.
{"title":"Improved coherence time of a non-Hermitian qubit in a PT-symmetric environment","authors":"Duttatreya , Ipsika Mohanty , Sanjib Dey","doi":"10.1016/j.aop.2025.170298","DOIUrl":"10.1016/j.aop.2025.170298","url":null,"abstract":"<div><div>Quantum computing’s potential for exponential speedup is fundamentally limited by decoherence, a phenomenon arising from environmental interactions. Non-Hermitian quantum mechanics, particularly <span><math><mrow><mi>P</mi><mi>T</mi></mrow></math></span>-symmetric systems, offers a novel framework for extending coherence times. This study examines a qubit’s coherence under non-Hermitian <span><math><mrow><mi>P</mi><mi>T</mi></mrow></math></span>-symmetric dynamics, highlighting significantly enhanced coherence times compared to Hermitian setups. The effect is especially pronounced when both the system and environment exhibit <span><math><mrow><mi>P</mi><mi>T</mi></mrow></math></span>-symmetry. Interestingly, greater environmental non-Hermiticity correlates with extended coherence, contrary to traditional expectations. These findings point to promising strategies for managing decoherence, which could significantly advance approaches to quantum information processing.</div></div>","PeriodicalId":8249,"journal":{"name":"Annals of Physics","volume":"484 ","pages":"Article 170298"},"PeriodicalIF":3.0,"publicationDate":"2025-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145621590","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-24DOI: 10.1016/j.aop.2025.170302
Shahid Chaudhary , Muhammad Danish Sultan , Talha Anwar , Atif Mossad Ali EI-Rehim , Farruh Atamurotov , Ali M. Mubaraki , Muhammad Hadi , M.A. Sayed
We study the gravitational lensing, shadow structure, and accretion dynamics of black holes modified by dark photon interactions arising from a hidden gauge symmetry. The metric incorporates Yukawa-type and magnetic dipole potentials sourced by dark photons. Using the Gauss–Bonnet theorem, we derive the weak deflection angle and show that the dark photon coupling , mass , and magnetic dipole ratio produce measurable deviations from general relativity. We further analyze light propagation in a plasma medium, where chromatic dispersion enhances the influence of the dark sector on the deflection angle. Extending the analysis to massive particles through the Jacobi metric approach, we demonstrate that velocity-dependent corrections cause slower particles to experience stronger deflection. The optical appearance of thin accretion disks is modeled using the Novikov–Thorne formalism and relativistic ray tracing, revealing that dark photon effects alter disk brightness and secondary image formation. Finally, static spherical accretion and shadow imaging analyses show that variations in and significantly modify the shadow boundary and ring luminosity, offering potential observational signatures of hidden-sector physics.
{"title":"Gravitational lensing, shadow images and accretion dynamics of dark photon corrected black holes","authors":"Shahid Chaudhary , Muhammad Danish Sultan , Talha Anwar , Atif Mossad Ali EI-Rehim , Farruh Atamurotov , Ali M. Mubaraki , Muhammad Hadi , M.A. Sayed","doi":"10.1016/j.aop.2025.170302","DOIUrl":"10.1016/j.aop.2025.170302","url":null,"abstract":"<div><div>We study the gravitational lensing, shadow structure, and accretion dynamics of black holes modified by dark photon interactions arising from a hidden <span><math><mrow><mi>U</mi><mrow><mo>(</mo><mn>1</mn><mo>)</mo></mrow></mrow></math></span> gauge symmetry. The metric incorporates Yukawa-type and magnetic dipole potentials sourced by dark photons. Using the Gauss–Bonnet theorem, we derive the weak deflection angle and show that the dark photon coupling <span><math><msub><mrow><mi>g</mi></mrow><mrow><mi>D</mi></mrow></msub></math></span>, mass <span><math><msub><mrow><mi>m</mi></mrow><mrow><msup><mrow><mi>A</mi></mrow><mrow><mo>′</mo></mrow></msup></mrow></msub></math></span>, and magnetic dipole ratio <span><math><mrow><msub><mrow><mi>μ</mi></mrow><mrow><mi>f</mi></mrow></msub><mo>/</mo><mi>Λ</mi></mrow></math></span> produce measurable deviations from general relativity. We further analyze light propagation in a plasma medium, where chromatic dispersion enhances the influence of the dark sector on the deflection angle. Extending the analysis to massive particles through the Jacobi metric approach, we demonstrate that velocity-dependent corrections cause slower particles to experience stronger deflection. The optical appearance of thin accretion disks is modeled using the Novikov–Thorne formalism and relativistic ray tracing, revealing that dark photon effects alter disk brightness and secondary image formation. Finally, static spherical accretion and shadow imaging analyses show that variations in <span><math><msub><mrow><mi>g</mi></mrow><mrow><mi>D</mi></mrow></msub></math></span> and <span><math><msub><mrow><mi>m</mi></mrow><mrow><msup><mrow><mi>A</mi></mrow><mrow><mo>′</mo></mrow></msup></mrow></msub></math></span> significantly modify the shadow boundary and ring luminosity, offering potential observational signatures of hidden-sector physics.</div></div>","PeriodicalId":8249,"journal":{"name":"Annals of Physics","volume":"485 ","pages":"Article 170302"},"PeriodicalIF":3.0,"publicationDate":"2025-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145692357","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-22DOI: 10.1016/j.aop.2025.170299
Alexey Dubinsky
We study axial gravitational perturbations of the Dymnikova regular black hole, an asymptotically flat spacetime in which the Schwarzschild singularity is replaced by a de Sitter core. Using the WKB method with Padé approximants, we compute grey-body factors, and absorption cross-sections, and test the recently proposed correspondence between quasinormal frequencies and transmission coefficients. We find that variations of the quantum parameter affect the effective potential only near the horizon, leading to minor deviations of grey-body factors and absorption cross-sections from the Schwarzschild case. As a result, the Hawking radiation spectrum is governed mainly by the modified Hawking temperature, with grey-body factors providing only subleading corrections. Unlike higher quasinormal overtones, which are highly sensitive to near-horizon deformations, the grey-body factors remain robust, a feature explicitly confirmed for the Dymnikova geometry. The correspondence between quasinormal modes and grey-body factors holds in our case with high accuracy for multipoles .
{"title":"Gravitational perturbations of Dymnikova black holes: Grey-body factors and absorption cross-sections","authors":"Alexey Dubinsky","doi":"10.1016/j.aop.2025.170299","DOIUrl":"10.1016/j.aop.2025.170299","url":null,"abstract":"<div><div>We study axial gravitational perturbations of the Dymnikova regular black hole, an asymptotically flat spacetime in which the Schwarzschild singularity is replaced by a de Sitter core. Using the WKB method with Padé approximants, we compute grey-body factors, and absorption cross-sections, and test the recently proposed correspondence between quasinormal frequencies and transmission coefficients. We find that variations of the quantum parameter <span><math><msub><mrow><mi>l</mi></mrow><mrow><mi>cr</mi></mrow></msub></math></span> affect the effective potential only near the horizon, leading to minor deviations of grey-body factors and absorption cross-sections from the Schwarzschild case. As a result, the Hawking radiation spectrum is governed mainly by the modified Hawking temperature, with grey-body factors providing only subleading corrections. Unlike higher quasinormal overtones, which are highly sensitive to near-horizon deformations, the grey-body factors remain robust, a feature explicitly confirmed for the Dymnikova geometry. The correspondence between quasinormal modes and grey-body factors holds in our case with high accuracy for multipoles <span><math><mrow><mi>ℓ</mi><mo>≥</mo><mn>2</mn></mrow></math></span>.</div></div>","PeriodicalId":8249,"journal":{"name":"Annals of Physics","volume":"485 ","pages":"Article 170299"},"PeriodicalIF":3.0,"publicationDate":"2025-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145600383","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-20DOI: 10.1016/j.aop.2025.170295
Frankbelson dos S. Azevedo , Faizuddin Ahmed , Edilberto O. Silva
In this paper, we investigate the Schrödinger equation in a three-dimensional helically twisted space characterized by a non-trivial torsion parameter. By applying exact separation of variables, we derive the radial equation governing the dynamics of quantum particles in this geometric background. Remarkably, the intrinsic coupling between angular and longitudinal momenta induced by the torsion gives rise to an attractive Coulomb-like potential term that emerges purely from the underlying geometry, without introducing any external fields or interactions. We obtain exact analytical solutions for the bound states, including both the energy spectrum and the normalized wave functions. Numerical calculations are also performed, and excellent agreement with the exact results is found. The interplay between the torsion parameter and the effective Coulomb-like interaction is analyzed in detail, revealing how geometric deformation gives rise to novel quantum confinement mechanisms in twisted spaces.
{"title":"Geometry-induced Coulomb-like potential in helically twisted quantum systems","authors":"Frankbelson dos S. Azevedo , Faizuddin Ahmed , Edilberto O. Silva","doi":"10.1016/j.aop.2025.170295","DOIUrl":"10.1016/j.aop.2025.170295","url":null,"abstract":"<div><div>In this paper, we investigate the Schrödinger equation in a three-dimensional helically twisted space characterized by a non-trivial torsion parameter. By applying exact separation of variables, we derive the radial equation governing the dynamics of quantum particles in this geometric background. Remarkably, the intrinsic coupling between angular and longitudinal momenta induced by the torsion gives rise to an attractive Coulomb-like potential term that emerges purely from the underlying geometry, without introducing any external fields or interactions. We obtain exact analytical solutions for the bound states, including both the energy spectrum and the normalized wave functions. Numerical calculations are also performed, and excellent agreement with the exact results is found. The interplay between the torsion parameter and the effective Coulomb-like interaction is analyzed in detail, revealing how geometric deformation gives rise to novel quantum confinement mechanisms in twisted spaces.</div></div>","PeriodicalId":8249,"journal":{"name":"Annals of Physics","volume":"484 ","pages":"Article 170295"},"PeriodicalIF":3.0,"publicationDate":"2025-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145577897","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-20DOI: 10.1016/j.aop.2025.170297
Kourosh Nozari, Hamed Ramezani
In this paper, we study the statistical mechanics within the polymer quantization framework in the semiclassical regime. We apply a non-canonical transformation to the phase space variables. Then, we use this non-canonical transformation to calculate the deformed density of states of the -dimensional phase space, which encompasses all polymer effects. In the next step, some thermodynamic features of a system of -dimensional harmonic oscillators are studied by computing the deformed partition function. The results show that the number of microstates decreases because there is an upper bound on the momentum within the polymer framework. We found that in the high-temperature regime, when the thermal de Broglie wavelength is close to the Planck length, degrees of freedom of the system are frozen in this setup. In other words, there is an effective reduction in space dimensions from to in the polymeric framework, which also signals the fractional dimension for odd-dimensional oscillators.
{"title":"Dimensional phenomenology in polymeric quantization framework","authors":"Kourosh Nozari, Hamed Ramezani","doi":"10.1016/j.aop.2025.170297","DOIUrl":"10.1016/j.aop.2025.170297","url":null,"abstract":"<div><div>In this paper, we study the statistical mechanics within the polymer quantization framework in the semiclassical regime. We apply a non-canonical transformation to the phase space variables. Then, we use this non-canonical transformation to calculate the deformed density of states of the <span><math><mrow><mn>2</mn><mi>n</mi></mrow></math></span>-dimensional phase space, which encompasses all polymer effects. In the next step, some thermodynamic features of a system of <span><math><mi>n</mi></math></span>-dimensional harmonic oscillators are studied by computing the deformed partition function. The results show that the number of microstates decreases because there is an upper bound on the momentum within the polymer framework. We found that in the high-temperature regime, when the thermal de Broglie wavelength is close to the Planck length, <span><math><mi>n</mi></math></span> degrees of freedom of the system are frozen in this setup. In other words, there is an effective reduction in space dimensions from <span><math><mi>n</mi></math></span> to <span><math><mfrac><mrow><mi>n</mi></mrow><mrow><mn>2</mn></mrow></mfrac></math></span> in the polymeric framework, which also signals the fractional dimension for odd-dimensional oscillators.</div></div>","PeriodicalId":8249,"journal":{"name":"Annals of Physics","volume":"484 ","pages":"Article 170297"},"PeriodicalIF":3.0,"publicationDate":"2025-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145577898","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-20DOI: 10.1016/j.aop.2025.170296
O. Hryhorchak , G. Panochko , V. Pastukhov
The properties of the one-dimensional population-imbalanced fermions are discussed. First, the system is assumed to be in the two-body resonance where all two-body scattering lengths diverge, and the only interaction between fermions that is taken into account is the short-range three-body one. In particular, we consider the situation when only one ‘flavor’ of fermions is macroscopically occupied, and there are exactly two atoms of the other two. This system supports the trimer and the medium-induced dimer states studied here in detail and shows evidence of color superfluidity. The impact of the two-body inter-impurity interaction that breaks the initial symmetry on the properties of the bipolaron is revealed.
{"title":"Bipolaron in one-dimensional fermions with three-body interaction","authors":"O. Hryhorchak , G. Panochko , V. Pastukhov","doi":"10.1016/j.aop.2025.170296","DOIUrl":"10.1016/j.aop.2025.170296","url":null,"abstract":"<div><div>The properties of the one-dimensional <span><math><mrow><mi>S</mi><mi>U</mi><mrow><mo>(</mo><mn>3</mn><mo>)</mo></mrow></mrow></math></span> population-imbalanced fermions are discussed. First, the system is assumed to be in the two-body resonance where all two-body scattering lengths diverge, and the only interaction between fermions that is taken into account is the short-range three-body one. In particular, we consider the situation when only one ‘flavor’ of fermions is macroscopically occupied, and there are exactly two atoms of the other two. This system supports the trimer and the medium-induced dimer states studied here in detail and shows evidence of color superfluidity. The impact of the two-body inter-impurity interaction that breaks the initial <span><math><mrow><mi>S</mi><mi>U</mi><mrow><mo>(</mo><mn>3</mn><mo>)</mo></mrow></mrow></math></span> symmetry on the properties of the bipolaron is revealed.</div></div>","PeriodicalId":8249,"journal":{"name":"Annals of Physics","volume":"484 ","pages":"Article 170296"},"PeriodicalIF":3.0,"publicationDate":"2025-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145577952","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-20DOI: 10.1016/j.aop.2025.170293
Marco Galoppo , Giorgio Torrieri
Motivated by known facts about effective field theory and non-Abelian gauge theory, we argue that the post-Newtonian approximation might fail even in the limit of weak fields and small velocities for wide-extended rotating bodies, where angular momentum spans significant spacetime curvature. We construct a novel dimensionless quantity that samples this breakdown, and we evaluate it by means of existing analytical solutions of rotating extended bodies and observational data. We give estimates for galaxies and binary systems, as well as our home in the Cosmos, Laniakea. We thus propose that a novel effective field theory of general relativity might be needed to account for the onset of nonlocal angular momentum effects.
{"title":"The need for a nonlocal expansion in general relativity","authors":"Marco Galoppo , Giorgio Torrieri","doi":"10.1016/j.aop.2025.170293","DOIUrl":"10.1016/j.aop.2025.170293","url":null,"abstract":"<div><div>Motivated by known facts about effective field theory and non-Abelian gauge theory, we argue that the post-Newtonian approximation might fail even in the limit of weak fields and small velocities for wide-extended rotating bodies, where angular momentum spans significant spacetime curvature. We construct a novel dimensionless quantity that samples this breakdown, and we evaluate it by means of existing analytical solutions of rotating extended bodies and observational data. We give estimates for galaxies and binary systems, as well as our home in the Cosmos, Laniakea. We thus propose that a novel effective field theory of general relativity might be needed to account for the onset of nonlocal angular momentum effects.</div></div>","PeriodicalId":8249,"journal":{"name":"Annals of Physics","volume":"484 ","pages":"Article 170293"},"PeriodicalIF":3.0,"publicationDate":"2025-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145577895","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-17DOI: 10.1016/j.aop.2025.170291
Arun Kumar , Sushant G. Ghosh
We investigate the strong gravitational lensing signatures of black holes (BH) surrounded by a novel class of cloud of strings (NCoS), characterized by additional parameters and beyond the Schwarzschild case. After deriving the photon sphere and critical impact parameter, we investigate the deflection angle in the strong-field regime, showing logarithmic divergence near the photon orbit. The lensing observables—angular image positions (), flux ratios (), and time delays between relativistic images—are computed for supermassive BHs M87 and Sgr A. Compared to Schwarzschild, Reissner-Nordström, and Letelier BHs, NCoS spacetime reveals distinguishable lensing features, with photon sphere radii and Einstein ring diameters varying non-monotonically with and . Applying our formalism to supermassive black holes M87* and Sgr A*, we find that the angular size of the photon ring and flux ratio provide stringent constraints on the NCoS parameters. EHT observations of M87* restrict the string cloud parameter to , while Sgr A* data impose tighter bounds () with , ruling out the pure Letelier limit () at confidence. Our results illustrate that NCoS BHs reconcile with EHT observations for a broader parameter range than earlier models, offering a viable framework to probe string-inspired modifications to general relativity in the strong-gravity regime.
我们研究了被一类新的弦云（NCoS）包围的黑洞（BH）的强引力透镜特征，其特征是超出史瓦西情况的附加参数|、|和c0。在推导出光子球和临界撞击参数后，我们研究了在强场区域的偏转角，在光子轨道附近显示出对数发散。透镜观测值——角图像位置（θ∞）、通量比（rmag）和相对论图像之间的时间延迟——计算了超大质量黑洞M87∗和Sgr A∗。与史瓦西黑洞、Reissner-Nordström和Letelier黑洞相比，NCoS时空显示出明显的透镜特征，光子球半径和爱因斯坦环直径随|、|和c0呈非单调变化。将我们的公式应用于超大质量黑洞M87*和Sgr A*，我们发现光子环的角尺寸θ∞和通量比rma对NCoS参数有严格的约束。M87*的EHT观测将弦云参数限制在0≤|a|≤0.56，而Sgr a *的数据在c0/M≥1.57的情况下施加了更严格的界限（|a|≤0.42），排除了纯Letelier极限（c0→0）在>；2σ置信度。我们的研究结果表明，与早期模型相比，NCoS黑洞在更宽的参数范围内与EHT观测相吻合，为探索强引力条件下弦启发的广义相对论修正提供了一个可行的框架。
{"title":"Strong gravitational lensing by black holes with a cloud of strings and constraints from EHT observations of M87* and Sgr A*","authors":"Arun Kumar , Sushant G. Ghosh","doi":"10.1016/j.aop.2025.170291","DOIUrl":"10.1016/j.aop.2025.170291","url":null,"abstract":"<div><div>We investigate the strong gravitational lensing signatures of black holes (BH) surrounded by a novel class of cloud of strings (NCoS), characterized by additional parameters <span><math><mrow><mo>|</mo><mi>a</mi><mo>|</mo></mrow></math></span> and <span><math><msub><mrow><mi>c</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span> beyond the Schwarzschild case. After deriving the photon sphere and critical impact parameter, we investigate the deflection angle in the strong-field regime, showing logarithmic divergence near the photon orbit. The lensing observables—angular image positions (<span><math><msub><mrow><mi>θ</mi></mrow><mrow><mi>∞</mi></mrow></msub></math></span>), flux ratios (<span><math><msub><mrow><mi>r</mi></mrow><mrow><mtext>mag</mtext></mrow></msub></math></span>), and time delays between relativistic images—are computed for supermassive BHs M87<span><math><msup><mrow></mrow><mrow><mo>∗</mo></mrow></msup></math></span> and Sgr A<span><math><msup><mrow></mrow><mrow><mo>∗</mo></mrow></msup></math></span>. Compared to Schwarzschild, Reissner-Nordström, and Letelier BHs, NCoS spacetime reveals distinguishable lensing features, with photon sphere radii and Einstein ring diameters varying non-monotonically with <span><math><mrow><mo>|</mo><mi>a</mi><mo>|</mo></mrow></math></span> and <span><math><msub><mrow><mi>c</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span>. Applying our formalism to supermassive black holes M87* and Sgr A*, we find that the angular size of the photon ring <span><math><msub><mrow><mi>θ</mi></mrow><mrow><mi>∞</mi></mrow></msub></math></span> and flux ratio <span><math><msub><mrow><mi>r</mi></mrow><mrow><mtext>mag</mtext></mrow></msub></math></span> provide stringent constraints on the NCoS parameters. EHT observations of M87* restrict the string cloud parameter to <span><math><mrow><mn>0</mn><mo>≤</mo><mrow><mo>|</mo><mi>a</mi><mo>|</mo></mrow><mo>≤</mo><mn>0</mn><mo>.</mo><mn>56</mn></mrow></math></span>, while Sgr A* data impose tighter bounds (<span><math><mrow><mrow><mo>|</mo><mi>a</mi><mo>|</mo></mrow><mo>≤</mo><mn>0</mn><mo>.</mo><mn>42</mn></mrow></math></span>) with <span><math><mrow><msub><mrow><mi>c</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>/</mo><mi>M</mi><mo>≳</mo><mn>1</mn><mo>.</mo><mn>57</mn></mrow></math></span>, ruling out the pure Letelier limit (<span><math><mrow><msub><mrow><mi>c</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>→</mo><mn>0</mn></mrow></math></span>) at <span><math><mrow><mo>></mo><mn>2</mn><mi>σ</mi></mrow></math></span> confidence. Our results illustrate that NCoS BHs reconcile with EHT observations for a broader parameter range than earlier models, offering a viable framework to probe string-inspired modifications to general relativity in the strong-gravity regime.</div></div>","PeriodicalId":8249,"journal":{"name":"Annals of Physics","volume":"484 ","pages":"Article 170291"},"PeriodicalIF":3.0,"publicationDate":"2025-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145577951","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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