This study reports the morphological characteristics of anomalous variations in Global Navigation Satellite System Total Electron Content(GNSS-TEC) prior to the strong local earthquakes(EQ) that occurred during the pe...This study reports the morphological characteristics of anomalous variations in Global Navigation Satellite System Total Electron Content(GNSS-TEC) prior to the strong local earthquakes(EQ) that occurred during the period of 2011-2015.We have analyzed 20 earthquakes of magnitude M> 5.6.A statistical technique is implemented on the data of six GNSS stations located in Tashkent,Kitab,and Maidanak in Uzbekistan,and Islamabad,Multan,Quetta in Pakistan.The results show continuous anomalous variations in TEC during 24 h befo re the occupancy of local earthquakes.It is shown that the precursors before the occurrence of strong earthquakes,in particular of magnitude 5.7,7.7,7.5,7.8 and 7.3 are detected near Eastern Uzbekistan(26 May 2013),Southwestern Pakistan(24 September 2013),Hindukush region of Afghanistan(26 October 2015),and Central Nepal(25 April 2015) and(12 May 2015),respectively.The ionospheric anomalies appearing before the strong earthquakes at six GNSS stations are registered in 14cases(70%) out of 20 selected EQs.It is depicted that anomalies referred to as ionospheric precursors appeared about 1-7 days prior to the occurrence of strong earthquakes.展开更多
The research presented in this paper discusses the impact that the parameters of charge(Q)and screening factor(γ)have on properties of the horizon and silhouette of rotating charged Mod Max black holes which were rev...The research presented in this paper discusses the impact that the parameters of charge(Q)and screening factor(γ)have on properties of the horizon and silhouette of rotating charged Mod Max black holes which were reviewed in[Eur.Phys.J.C(2022)82:1155]recently,building upon previous findings in the field.Furthermore,the study explores the behavior of null geodesics,which can help us better understand the apparent shape of the black hole’s silhouette,as well as the distortion parameter and approximate radii of the silhouette that are influenced by the aforementioned parameters,and there are some values of parameter Q which corresponds to data from the Event Horizon Telescope(EHT).Notably,we explore the distortion parameter and approximate radii of the silhouette,revealing that while an increase inγleads to a growth in silhouette radius(Rs),it simultaneously reduces the distortion rate(δs).Conversely,heightened Q charge results in a reduction of Rsaccompanied by an increase inδs.Lastly,the paper analyzes the effects of the black hole’s parameters on the effective potential and energy emission:the peak value of the energy emission rate experiences a decrease as the screening factor(γ)increases,while it increases with higher values of the charge parameter(Q).展开更多
In this study,we investigated the gravitational weak lensing and shadow of the Ellis-Bronnikov wormhole.First,we studied the photon motion in a plasma medium and a wormhole shadow.It was shown that the radius of the p...In this study,we investigated the gravitational weak lensing and shadow of the Ellis-Bronnikov wormhole.First,we studied the photon motion in a plasma medium and a wormhole shadow.It was shown that the radius of the photon sphere of the Ellis-Bronnikov wormhole and the size of the wormhole shadow become larger under the influence of the parameter a.The upper limit of the parameter a in the Ellis-Bronnikov wormhole spacetime was obtained.Second,we investigated the weak gravitational lensing for the Ellis-Bronnikov wormhole and calculated the deflection angle for uniform and non uniform plasma cases.The value of the deflection angle for uniform plasma increased with the increase in plasma parameter value,and vice versa for non uniform plasma.We found that,under the influence of the parameter a,the values of the deflection angles for two cases decreased.Finally,we investigated the magnification of image brightness using the deflection angle of the light rays around the wormhole in the EllisBronnikov theory.展开更多
In this study,we explore the properties of a non-rotating black hole in the Einstein-Maxwell-scalar(EMS)theory and investigate the luminosity of the accretion disk surrounding it.We determine all the orbital parameter...In this study,we explore the properties of a non-rotating black hole in the Einstein-Maxwell-scalar(EMS)theory and investigate the luminosity of the accretion disk surrounding it.We determine all the orbital parameters of particles in the accretion disk,including the radius of the innermost stable circular orbit(ISCO)with angular velocity,angular momentum,and energy.Further,we study the radiative efficiency for different values of black hole parameters.Finally,we analyze the flux,differential luminosity,and temperature of the accretion disk.展开更多
In this study,we have investigated the mathematical components of the Dirac equation in curved spacetime and how they can be applied to the analysis of neutrino oscillations.More specifically,we have developed a metho...In this study,we have investigated the mathematical components of the Dirac equation in curved spacetime and how they can be applied to the analysis of neutrino oscillations.More specifically,we have developed a method for calculating the phase shift in flavor neutrino oscillations by utilizing a Taylor series expansion of the action that takes into account△m^(4) orders.In addition,we have used this method to assess how the phase difference in neutrino mass eigenstates changes according to the gravitational field described by the Johannsen spacetime.展开更多
In the present study,we investigate the dynamics of test particles around a Schwarzschild black hole surrounded by quintessence and immersed in a scalar string cloud field.We start our study by defining the possible v...In the present study,we investigate the dynamics of test particles around a Schwarzschild black hole surrounded by quintessence and immersed in a scalar string cloud field.We start our study by defining the possible values of the quintessence and cloud of string parameters corresponding to the existence of the black hole horizon for fixed values of the parameters of the equation of state for dark energy.We also study the effects of the effective potential on the circular motion,energy,and angular momentum of the test particles together with the innermost stable circular orbits(ISCOs).We investigate the fundamental frequencies in the particle oscillations along stable circular orbits.We relate the stability of the orbits to the Lyapunov exponent,and the chaotic behavior is studied graphically.Finally,we apply the fundamental frequencies to describe quasiperiodic oscillations(QPOs)and find that,in the presence of both fields,low-frequency twin-peak QPOs are not observed.In addition,we obtain the constraint values for the string cloud parameter and mass of the black hole candidates located in the center of the microquasars GRO J1655-40 and GRS 1915+105 as well as the Milky Way galaxy.展开更多
In this study,we observe that,in the presence of the string cloud parameter a and the quintessence parameterγ,with the equation of state parameter,ω_(q) = -2/3the radius of the shadow of the Schwarzschild black hole...In this study,we observe that,in the presence of the string cloud parameter a and the quintessence parameterγ,with the equation of state parameter,ω_(q) = -2/3the radius of the shadow of the Schwarzschild black hole increases as compared with that in the pure Schwarzschild black hole case.The existence of both quintessential dark energy and the cloud of strings increases the shadow size;hence,the strength of the gravitational field around the Schwarzschild black hole increases.Using the data collected by the Event Horizon Telescope(EHT)collaboration for M87*and Sgr A*,we obtain upper bounds on the values of a andγ.Further,we see the effects of a andγon the rate of emission energy for the Schwarzschild black hole.We notice that the rate of emission energy is higher in the presence of clouds of strings and quintessence.Moreover,we study the weak deflection angle using the Gauss-Bonnet theorem.We show the influence of a andγon the weak deflection angle.We notice that both a andγincrease the deflection angleα.展开更多
We study the particle motion around a black hole(BH)in Horava-Lifshitz(HL)gravity with the Kehagias-Sfetsos(KS)parameter.First,the innermost stable circular orbit(ISCO)is obtained for massive particles around the BH i...We study the particle motion around a black hole(BH)in Horava-Lifshitz(HL)gravity with the Kehagias-Sfetsos(KS)parameter.First,the innermost stable circular orbit(ISCO)is obtained for massive particles around the BH in HL gravity.We find that the radii of the ISCOs decrease as the KS parameter decreases,meaning that the parameterΩcauses the orbits of particles to move inward with respect to that of the Schwarzschild BH case.Then,the optical properties of a KS BH are studied in detail,that is,the BH shadow and gravitational weak lensing.We demonstrate that the size of the BH shadow decreases under the influence of the KS parameter.展开更多
The effect of spacetime curvature on photon motion may offer an opportunity to propose new tests on gravity theories.In this study,we investigate and focus on the massless(photon)particle motion around blackbounce gra...The effect of spacetime curvature on photon motion may offer an opportunity to propose new tests on gravity theories.In this study,we investigate and focus on the massless(photon)particle motion around blackbounce gravity.We analyze the horizon structure around a gravitational compact object described by black-bounce spacetime.The photon motion and the effect of gravitational weak lensing in vacuum and plasma are discussed,and the shadow radius of the compact object is also studied in black-bounce spacetime.Additionally,the magnification of the image is studied using the deflection angle of light rays.展开更多
基金supported by the National Natural Science Foundation of China (42030202)。
文摘This study reports the morphological characteristics of anomalous variations in Global Navigation Satellite System Total Electron Content(GNSS-TEC) prior to the strong local earthquakes(EQ) that occurred during the period of 2011-2015.We have analyzed 20 earthquakes of magnitude M> 5.6.A statistical technique is implemented on the data of six GNSS stations located in Tashkent,Kitab,and Maidanak in Uzbekistan,and Islamabad,Multan,Quetta in Pakistan.The results show continuous anomalous variations in TEC during 24 h befo re the occupancy of local earthquakes.It is shown that the precursors before the occurrence of strong earthquakes,in particular of magnitude 5.7,7.7,7.5,7.8 and 7.3 are detected near Eastern Uzbekistan(26 May 2013),Southwestern Pakistan(24 September 2013),Hindukush region of Afghanistan(26 October 2015),and Central Nepal(25 April 2015) and(12 May 2015),respectively.The ionospheric anomalies appearing before the strong earthquakes at six GNSS stations are registered in 14cases(70%) out of 20 selected EQs.It is depicted that anomalies referred to as ionospheric precursors appeared about 1-7 days prior to the occurrence of strong earthquakes.
基金partly supported by Research Grant F-FA-2021510 of the Uzbekistan Ministry for Innovative Developmentsupport received from the Scientific and Technological Research Council of Türkiye(TüBITAK),the Abdus Salam International Centre for Theoretical Physics,Trieste,Italy and the Sponsoring Consortium for Open Access Publishing in Particle Physics(SCOAP3)。
文摘The research presented in this paper discusses the impact that the parameters of charge(Q)and screening factor(γ)have on properties of the horizon and silhouette of rotating charged Mod Max black holes which were reviewed in[Eur.Phys.J.C(2022)82:1155]recently,building upon previous findings in the field.Furthermore,the study explores the behavior of null geodesics,which can help us better understand the apparent shape of the black hole’s silhouette,as well as the distortion parameter and approximate radii of the silhouette that are influenced by the aforementioned parameters,and there are some values of parameter Q which corresponds to data from the Event Horizon Telescope(EHT).Notably,we explore the distortion parameter and approximate radii of the silhouette,revealing that while an increase inγleads to a growth in silhouette radius(Rs),it simultaneously reduces the distortion rate(δs).Conversely,heightened Q charge results in a reduction of Rsaccompanied by an increase inδs.Lastly,the paper analyzes the effects of the black hole’s parameters on the effective potential and energy emission:the peak value of the energy emission rate experiences a decrease as the screening factor(γ)increases,while it increases with higher values of the charge parameter(Q).
基金partly Supported by Grants F-FA-2021-432,F-FA-2021-510,and MRB-2021-527 of the Ministry of Higher Education,Science and Innovations of the Republic of Uzbekistan。
文摘In this study,we investigated the gravitational weak lensing and shadow of the Ellis-Bronnikov wormhole.First,we studied the photon motion in a plasma medium and a wormhole shadow.It was shown that the radius of the photon sphere of the Ellis-Bronnikov wormhole and the size of the wormhole shadow become larger under the influence of the parameter a.The upper limit of the parameter a in the Ellis-Bronnikov wormhole spacetime was obtained.Second,we investigated the weak gravitational lensing for the Ellis-Bronnikov wormhole and calculated the deflection angle for uniform and non uniform plasma cases.The value of the deflection angle for uniform plasma increased with the increase in plasma parameter value,and vice versa for non uniform plasma.We found that,under the influence of the parameter a,the values of the deflection angles for two cases decreased.Finally,we investigated the magnification of image brightness using the deflection angle of the light rays around the wormhole in the EllisBronnikov theory.
基金Supported by the National Natural Science Foundation of China (11675143, 11975203)the National Key Research and Development Program of China(2020YFC2201503)。
文摘In this study,we explore the properties of a non-rotating black hole in the Einstein-Maxwell-scalar(EMS)theory and investigate the luminosity of the accretion disk surrounding it.We determine all the orbital parameters of particles in the accretion disk,including the radius of the innermost stable circular orbit(ISCO)with angular velocity,angular momentum,and energy.Further,we study the radiative efficiency for different values of black hole parameters.Finally,we analyze the flux,differential luminosity,and temperature of the accretion disk.
基金Supported by the Grants F-FA-2021-510 from the Uzbekistan Ministry for Innovative Development。
文摘In this study,we have investigated the mathematical components of the Dirac equation in curved spacetime and how they can be applied to the analysis of neutrino oscillations.More specifically,we have developed a method for calculating the phase shift in flavor neutrino oscillations by utilizing a Taylor series expansion of the action that takes into account△m^(4) orders.In addition,we have used this method to assess how the phase difference in neutrino mass eigenstates changes according to the gravitational field described by the Johannsen spacetime.
基金Supported by the F-FA-2021-510 Grant of the Ministry of Innovative Development of Uzbekistan。
文摘In the present study,we investigate the dynamics of test particles around a Schwarzschild black hole surrounded by quintessence and immersed in a scalar string cloud field.We start our study by defining the possible values of the quintessence and cloud of string parameters corresponding to the existence of the black hole horizon for fixed values of the parameters of the equation of state for dark energy.We also study the effects of the effective potential on the circular motion,energy,and angular momentum of the test particles together with the innermost stable circular orbits(ISCOs).We investigate the fundamental frequencies in the particle oscillations along stable circular orbits.We relate the stability of the orbits to the Lyapunov exponent,and the chaotic behavior is studied graphically.Finally,we apply the fundamental frequencies to describe quasiperiodic oscillations(QPOs)and find that,in the presence of both fields,low-frequency twin-peak QPOs are not observed.In addition,we obtain the constraint values for the string cloud parameter and mass of the black hole candidates located in the center of the microquasars GRO J1655-40 and GRS 1915+105 as well as the Milky Way galaxy.
基金the Grant No.ZC304022919 to support his Postdoctoral Fellowship at Zhejiang Normal Universitythe support of Inha University in Tashkent and research work has been supported by the Visitor Research Fellowship at Zhejiang Normal Universitysupported by Research Grant FZ-20200929344,F-FA-2021-510 and F-FA-2021-432 of the Uzbekistan Ministry for Innovative Development。
文摘In this study,we observe that,in the presence of the string cloud parameter a and the quintessence parameterγ,with the equation of state parameter,ω_(q) = -2/3the radius of the shadow of the Schwarzschild black hole increases as compared with that in the pure Schwarzschild black hole case.The existence of both quintessential dark energy and the cloud of strings increases the shadow size;hence,the strength of the gravitational field around the Schwarzschild black hole increases.Using the data collected by the Event Horizon Telescope(EHT)collaboration for M87*and Sgr A*,we obtain upper bounds on the values of a andγ.Further,we see the effects of a andγon the rate of emission energy for the Schwarzschild black hole.We notice that the rate of emission energy is higher in the presence of clouds of strings and quintessence.Moreover,we study the weak deflection angle using the Gauss-Bonnet theorem.We show the influence of a andγon the weak deflection angle.We notice that both a andγincrease the deflection angleα.
基金partly supported by Grants F-FA-2021-432,F-FA-2021-510,and MRB-2021-527 of the Ministry of Higher Education,Science and Innovations of the Republic of Uzbekistan
文摘We study the particle motion around a black hole(BH)in Horava-Lifshitz(HL)gravity with the Kehagias-Sfetsos(KS)parameter.First,the innermost stable circular orbit(ISCO)is obtained for massive particles around the BH in HL gravity.We find that the radii of the ISCOs decrease as the KS parameter decreases,meaning that the parameterΩcauses the orbits of particles to move inward with respect to that of the Schwarzschild BH case.Then,the optical properties of a KS BH are studied in detail,that is,the BH shadow and gravitational weak lensing.We demonstrate that the size of the BH shadow decreases under the influence of the KS parameter.
基金Supported by Grant F-FA-2021-510 of the Uzbekistan Ministry for Innovative Development。
文摘The effect of spacetime curvature on photon motion may offer an opportunity to propose new tests on gravity theories.In this study,we investigate and focus on the massless(photon)particle motion around blackbounce gravity.We analyze the horizon structure around a gravitational compact object described by black-bounce spacetime.The photon motion and the effect of gravitational weak lensing in vacuum and plasma are discussed,and the shadow radius of the compact object is also studied in black-bounce spacetime.Additionally,the magnification of the image is studied using the deflection angle of light rays.
