Pub Date : 2020-11-11DOI: 10.1142/S0217732321501005
A. Paliathanasis
We investigate the existence of Liouville integrable cosmological models in hybrid metric-Palatini theory. Specifically we use the symmetry conditions for the existence of quadratic in the momentum conservation laws for the field equations as constraint conditions for the determination of the unknown functional form of the theory. The exact and analytic solutions of the integrable systems which found in this study are presented in terms of quadratics and Laurent expansions.
{"title":"New cosmological solutions in hybrid metric-Palatini gravity from dynamical symmetries","authors":"A. Paliathanasis","doi":"10.1142/S0217732321501005","DOIUrl":"https://doi.org/10.1142/S0217732321501005","url":null,"abstract":"We investigate the existence of Liouville integrable cosmological models in hybrid metric-Palatini theory. Specifically we use the symmetry conditions for the existence of quadratic in the momentum conservation laws for the field equations as constraint conditions for the determination of the unknown functional form of the theory. The exact and analytic solutions of the integrable systems which found in this study are presented in terms of quadratics and Laurent expansions.","PeriodicalId":8455,"journal":{"name":"arXiv: General Relativity and Quantum Cosmology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81148735","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 : 2020-11-11DOI: 10.1103/physrevd.103.024007
Y. Lim
In this paper we study the motion of photons or massless particles in the C-metric with cosmological constant. The Hamilton--Jacobi equations are known to be completely separable, giving a Carter-like quantity $Q$ which is a constant of motion. All possible trajectories are classified according to a two-dimensional parameter space representing the particle's angular momentum and energy scaled in units of $Q$. Exact solutions are given in the C-metric coordinates in terms of Jacobi elliptic functions. Using the exact solutions, we find examples of periodic orbits on the photon surface.
{"title":"Null geodesics in the \u0000C\u0000 metric with a cosmological constant","authors":"Y. Lim","doi":"10.1103/physrevd.103.024007","DOIUrl":"https://doi.org/10.1103/physrevd.103.024007","url":null,"abstract":"In this paper we study the motion of photons or massless particles in the C-metric with cosmological constant. The Hamilton--Jacobi equations are known to be completely separable, giving a Carter-like quantity $Q$ which is a constant of motion. All possible trajectories are classified according to a two-dimensional parameter space representing the particle's angular momentum and energy scaled in units of $Q$. Exact solutions are given in the C-metric coordinates in terms of Jacobi elliptic functions. Using the exact solutions, we find examples of periodic orbits on the photon surface.","PeriodicalId":8455,"journal":{"name":"arXiv: General Relativity and Quantum Cosmology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86286518","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 : 2020-11-09DOI: 10.20944/preprints202011.0405.v1
Teng Zhang, J. Bentley, H. Miao
Quantum noise limits the sensitivity of laser interferometric gravitational-wave detectors. Given the state-of-the-art optics, the optical losses define the lower bound of best possible quantum-limited detector sensitivity. In this work, we come up with the configuration which allows to saturate this lower bound by converting the signal recycling cavity to be a broadband signal amplifier using an active optomechanical filter. We will show the difference and advantage of such a broadband signal recycling scheme compared with the previous white-light-cavity scheme using the optomechanical filter in [Phys.Rev.Lett.115.211104 (2015)]. The drawback is that the new scheme is more susceptible to the thermal noise of the mechanical oscillator. To suppress the radiation pressure noise which rises along with the signal amplification, squeezing with input/output filter cavities and heavier test mass are used in this work.
量子噪声限制了激光干涉引力波探测器的灵敏度。考虑到最先进的光学技术，光学损耗定义了最佳量子限制探测器灵敏度的下界。在这项工作中，我们提出了一种配置，通过使用有源光机械滤波器将信号回收腔转换为宽带信号放大器，从而使该下界饱和。我们将在[phys.rev . letter .115.211104(2015)]中展示这种宽带信号回收方案与先前使用光机械滤波器的白光腔方案的区别和优势。缺点是新方案更容易受到机械振荡器热噪声的影响。为了抑制随着信号放大而上升的辐射压力噪声，采用了输入/输出滤波器腔挤压和加大测试质量的方法。
{"title":"A broadband signal recycling scheme for saturating the quantum limit from optical losses","authors":"Teng Zhang, J. Bentley, H. Miao","doi":"10.20944/preprints202011.0405.v1","DOIUrl":"https://doi.org/10.20944/preprints202011.0405.v1","url":null,"abstract":"Quantum noise limits the sensitivity of laser interferometric gravitational-wave detectors. Given the state-of-the-art optics, the optical losses define the lower bound of best possible quantum-limited detector sensitivity. In this work, we come up with the configuration which allows to saturate this lower bound by converting the signal recycling cavity to be a broadband signal amplifier using an active optomechanical filter. We will show the difference and advantage of such a broadband signal recycling scheme compared with the previous white-light-cavity scheme using the optomechanical filter in [Phys.Rev.Lett.115.211104 (2015)]. The drawback is that the new scheme is more susceptible to the thermal noise of the mechanical oscillator. To suppress the radiation pressure noise which rises along with the signal amplification, squeezing with input/output filter cavities and heavier test mass are used in this work.","PeriodicalId":8455,"journal":{"name":"arXiv: General Relativity and Quantum Cosmology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77283795","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 : 2020-11-09DOI: 10.1142/s0219887821500596
S. Mendoza, S. Silva
We show that the matter Lagrangian of an ideal fluid equals (up to a sign -depending on its definition and on the chosen signature of the metric) the total energy density of the fluid, i.e. rest energy density plus internal energy density.
{"title":"The matter Lagrangian of an ideal fluid","authors":"S. Mendoza, S. Silva","doi":"10.1142/s0219887821500596","DOIUrl":"https://doi.org/10.1142/s0219887821500596","url":null,"abstract":"We show that the matter Lagrangian of an ideal fluid equals (up to a sign -depending on its definition and on the chosen signature of the metric) the total energy density of the fluid, i.e. rest energy density plus internal energy density.","PeriodicalId":8455,"journal":{"name":"arXiv: General Relativity and Quantum Cosmology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91412762","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 : 2020-11-06DOI: 10.1103/PHYSREVD.103.083529
P. Małkiewicz, Artur Miroszewski
Quantum cosmological models are commonly described by means of semiclassical approximations in which a smooth evolution of the expectation values of geometry operators replaces the classical and singular dynamics. The advantage of such descriptions is that they are relatively simple and display the classical behavior for large universes. However, they may "smooth out" an important inner structure to include which a more nuanced treatment is needed. The purpose of the present work is to investigate this inner structure and its influence on primordial gravitational waves. To this end we quantize a model of the Friedmann-Lemaitre-Robertson-Walker universe filled with a "linear" barotropic cosmological fluid and with gravitational waves. The quantization yields an equation of motion for the Fourier modes of gravitational radiation, which is a quantum extension to the usual parametric oscillator equation for gravitational waves propagating in an expanding universe. The two quantum effects from the cosmological background that enter the enhanced equation of motion are (i) a repulsive potential resolving the big bang singularity and replacing it with a Big Bounce; and (ii) uncertainties in the numerical values for the background spacetime dynamical variables. First we study the former effect and its consequences for the primordial amplitude spectrum and carefully discuss the physical scales and parameters of the model. Next we investigate the latter effect, in particular the extent to which it may affect the primordial amplitude of gravitational waves.
{"title":"Dynamics of primordial fields in quantum cosmological spacetimes","authors":"P. Małkiewicz, Artur Miroszewski","doi":"10.1103/PHYSREVD.103.083529","DOIUrl":"https://doi.org/10.1103/PHYSREVD.103.083529","url":null,"abstract":"Quantum cosmological models are commonly described by means of semiclassical approximations in which a smooth evolution of the expectation values of geometry operators replaces the classical and singular dynamics. The advantage of such descriptions is that they are relatively simple and display the classical behavior for large universes. However, they may \"smooth out\" an important inner structure to include which a more nuanced treatment is needed. The purpose of the present work is to investigate this inner structure and its influence on primordial gravitational waves. To this end we quantize a model of the Friedmann-Lemaitre-Robertson-Walker universe filled with a \"linear\" barotropic cosmological fluid and with gravitational waves. The quantization yields an equation of motion for the Fourier modes of gravitational radiation, which is a quantum extension to the usual parametric oscillator equation for gravitational waves propagating in an expanding universe. The two quantum effects from the cosmological background that enter the enhanced equation of motion are (i) a repulsive potential resolving the big bang singularity and replacing it with a Big Bounce; and (ii) uncertainties in the numerical values for the background spacetime dynamical variables. First we study the former effect and its consequences for the primordial amplitude spectrum and carefully discuss the physical scales and parameters of the model. Next we investigate the latter effect, in particular the extent to which it may affect the primordial amplitude of gravitational waves.","PeriodicalId":8455,"journal":{"name":"arXiv: General Relativity and Quantum Cosmology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82508467","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 : 2020-11-06DOI: 10.1103/PHYSREVRESEARCH.3.013147
Pawan Kumar Gupta, J. Steinhoff, T. Hinderer
Gravitomagnetic quasi-normal modes of neutron stars are resonantly excited by tidal effects during a binary inspiral, leading to a potentially measurable effect in the gravitational-wave signal. We take an important step towards incorporating these effects in waveform models by developing a relativistic effective action for the gravitomagnetic dynamics that clarifies a number of subtleties. Working in the slow-rotation limit, we first consider the post-Newtonian approximation and explicitly derive the effective action from the equations of motion. We demonstrate that this formulation opens a way to compute mode frequencies, yields insights into the relevant matter variables, and elucidates the role of a shift symmetry of the fluid properties under a displacement of the gravitomagnetic mode amplitudes. We then construct a fully relativistic action based on the symmetries and a power counting scheme. This action involves four coupling coefficients that depend on the internal structure of the neutron star and characterize the key matter parameters imprinted in the gravitational waves. We show that, after fixing one of the coefficients by normalization, the other three directly involve the two kinds of gravitomagnetic Love numbers (static and irrotational), and the mode frequencies. We discuss several interesting features and dynamical consequences of this action, and analyze the frequency-domain response function (the frequency-dependent ratio between the induced flux quadrupole and the external gravitomagnetic field), and a corresponding Love operator representing the time-domain response. Our results provide the foundation for deriving precision predictions of gravitomagnetic effects, and the nuclear physics they encode, for gravitational-wave astronomy.
{"title":"Relativistic effective action of dynamical gravitomagnetic tides for slowly rotating neutron stars","authors":"Pawan Kumar Gupta, J. Steinhoff, T. Hinderer","doi":"10.1103/PHYSREVRESEARCH.3.013147","DOIUrl":"https://doi.org/10.1103/PHYSREVRESEARCH.3.013147","url":null,"abstract":"Gravitomagnetic quasi-normal modes of neutron stars are resonantly excited by tidal effects during a binary inspiral, leading to a potentially measurable effect in the gravitational-wave signal. We take an important step towards incorporating these effects in waveform models by developing a relativistic effective action for the gravitomagnetic dynamics that clarifies a number of subtleties. Working in the slow-rotation limit, we first consider the post-Newtonian approximation and explicitly derive the effective action from the equations of motion. We demonstrate that this formulation opens a way to compute mode frequencies, yields insights into the relevant matter variables, and elucidates the role of a shift symmetry of the fluid properties under a displacement of the gravitomagnetic mode amplitudes. We then construct a fully relativistic action based on the symmetries and a power counting scheme. This action involves four coupling coefficients that depend on the internal structure of the neutron star and characterize the key matter parameters imprinted in the gravitational waves. We show that, after fixing one of the coefficients by normalization, the other three directly involve the two kinds of gravitomagnetic Love numbers (static and irrotational), and the mode frequencies. We discuss several interesting features and dynamical consequences of this action, and analyze the frequency-domain response function (the frequency-dependent ratio between the induced flux quadrupole and the external gravitomagnetic field), and a corresponding Love operator representing the time-domain response. Our results provide the foundation for deriving precision predictions of gravitomagnetic effects, and the nuclear physics they encode, for gravitational-wave astronomy.","PeriodicalId":8455,"journal":{"name":"arXiv: General Relativity and Quantum Cosmology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74243335","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 : 2020-11-05DOI: 10.1103/PHYSREVD.103.084001
E. Khalouei, H. Ghodsi, S. Rahvar, J. Abedi
The analysis of Gravitational Waves (GW) data from the Advanced LIGO provides the mass of each companion of binary black holes as the source of GWs. The observations reveal that the mass of events corresponding to the binary black holes are much larger than the mass of astrophysical black holes. In this work, we suggest the Primordial Black Holes (PBHs) as the source of LIGO events. Assuming that $100%$ of the dark matter is made of PBHs, we estimate the rate at which these objects make binaries, merge and produce GWs as a function of redshift. The gravitational lensing of GWs by PBHs can also enhance the amplitude of the strain. We simulate GWs sourced by the binary PBHs, with the detection threshold of $S/N>10$ for both Livingston and Handford detectors. For the log-normal mass function of PBHs, we generate the expected distribution of events and compare our results with the observed events and find the best value of the mass function parameters (i.e $M_c =25 M_odot$ and $sigma=0.6$) in the lognormal mass function. Comparing the expected number of events with the number of observed ones reveals that even assuming all the dark matter is made of PBHs are not enough to produce the observed GW events and the astrophysical black holes should have the main contribution in the observed GW events.
{"title":"Possibility of primordial black holes as the source of gravitational wave events in the advanced LIGO detector","authors":"E. Khalouei, H. Ghodsi, S. Rahvar, J. Abedi","doi":"10.1103/PHYSREVD.103.084001","DOIUrl":"https://doi.org/10.1103/PHYSREVD.103.084001","url":null,"abstract":"The analysis of Gravitational Waves (GW) data from the Advanced LIGO provides the mass of each companion of binary black holes as the source of GWs. The observations reveal that the mass of events corresponding to the binary black holes are much larger than the mass of astrophysical black holes. In this work, we suggest the Primordial Black Holes (PBHs) as the source of LIGO events. Assuming that $100%$ of the dark matter is made of PBHs, we estimate the rate at which these objects make binaries, merge and produce GWs as a function of redshift. The gravitational lensing of GWs by PBHs can also enhance the amplitude of the strain. We simulate GWs sourced by the binary PBHs, with the detection threshold of $S/N>10$ for both Livingston and Handford detectors. For the log-normal mass function of PBHs, we generate the expected distribution of events and compare our results with the observed events and find the best value of the mass function parameters (i.e $M_c =25 M_odot$ and $sigma=0.6$) in the lognormal mass function. Comparing the expected number of events with the number of observed ones reveals that even assuming all the dark matter is made of PBHs are not enough to produce the observed GW events and the astrophysical black holes should have the main contribution in the observed GW events.","PeriodicalId":8455,"journal":{"name":"arXiv: General Relativity and Quantum Cosmology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79417537","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 : 2020-11-04DOI: 10.1103/PhysRevD.103.104031
Minyong Guo, Sijie Gao
Light rings (LRs) play an important role in gravitational wave observations and black hole photographs. In this letter, we investigate general features of LRs in stationary, axisymmetric, asymptotically flat spacetimes with or without horizons. For a nonextremal black hole, we show explicitly that there always exist at least two radially unstable LRs propagating in opposite directions on the equatorial plane. For an extremal black hole, we show that there exists at least one retrograde LR. Our method also applies to horizonless spacetimes and we prove that there always exist even number of LRs on the equatorial plane, where the outermost one is unstable in the radial direction. Only some natural and generic assumptions are used in our proof. The results are applicable to general relativity as well as most modified theories of gravity. In contrast to previous works on this issue, we obtain stronger and clearer results with a much more straightforward approach.
{"title":"Universal Properties of Light Rings for Stationary Axisymmetric Spacetimes.","authors":"Minyong Guo, Sijie Gao","doi":"10.1103/PhysRevD.103.104031","DOIUrl":"https://doi.org/10.1103/PhysRevD.103.104031","url":null,"abstract":"Light rings (LRs) play an important role in gravitational wave observations and black hole photographs. In this letter, we investigate general features of LRs in stationary, axisymmetric, asymptotically flat spacetimes with or without horizons. For a nonextremal black hole, we show explicitly that there always exist at least two radially unstable LRs propagating in opposite directions on the equatorial plane. For an extremal black hole, we show that there exists at least one retrograde LR. Our method also applies to horizonless spacetimes and we prove that there always exist even number of LRs on the equatorial plane, where the outermost one is unstable in the radial direction. Only some natural and generic assumptions are used in our proof. The results are applicable to general relativity as well as most modified theories of gravity. In contrast to previous works on this issue, we obtain stronger and clearer results with a much more straightforward approach.","PeriodicalId":8455,"journal":{"name":"arXiv: General Relativity and Quantum Cosmology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80369982","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 : 2020-11-02DOI: 10.1103/PhysRevD.102.101501
M. Ruggiero, A. Ortolan
Using the construction of the Fermi frame, the field of a gravitational wave can be described in terms of gravito-electromagnetic fields that are transverse to the propagation direction and orthogonal to each other. In particular, the gravito-magnetic field acts on spinning particles and we show that, due to the action of the gravitational wave field, a new phenomenon, that we call gravito-magnetic resonance, may appear. We give both a classical and a quantum description of this phenomenon and suggest that it can be used as the basis for a new type of gravitational wave detectors. Our results highlight the effectiveness of collective spin excitations, e.g. spin waves in magnetized materials, in detecting high frequency gravitational waves. Here we suggest that, when gravitational waves induce a precession of the electron spin, power is released in the ferromagnetic resonant mode endowed with quadrupole symmetry of a magnetized sphere. This offers a possible path to the detection of the gravito-magnetic effects of a gravitational wave.
{"title":"Gravitomagnetic resonance in the field of a gravitational wave","authors":"M. Ruggiero, A. Ortolan","doi":"10.1103/PhysRevD.102.101501","DOIUrl":"https://doi.org/10.1103/PhysRevD.102.101501","url":null,"abstract":"Using the construction of the Fermi frame, the field of a gravitational wave can be described in terms of gravito-electromagnetic fields that are transverse to the propagation direction and orthogonal to each other. In particular, the gravito-magnetic field acts on spinning particles and we show that, due to the action of the gravitational wave field, a new phenomenon, that we call gravito-magnetic resonance, may appear. We give both a classical and a quantum description of this phenomenon and suggest that it can be used as the basis for a new type of gravitational wave detectors. Our results highlight the effectiveness of collective spin excitations, e.g. spin waves in magnetized materials, in detecting high frequency gravitational waves. Here we suggest that, when gravitational waves induce a precession of the electron spin, power is released in the ferromagnetic resonant mode endowed with quadrupole symmetry of a magnetized sphere. This offers a possible path to the detection of the gravito-magnetic effects of a gravitational wave.","PeriodicalId":8455,"journal":{"name":"arXiv: General Relativity and Quantum Cosmology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81998492","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 : 2020-10-31DOI: 10.1103/PHYSREVD.103.066016
Refik Mansuroglu, H. Sahlmann
We define and study kinematical observables involving fermion spin, such as the total spin of a collection of particles, in loop quantum gravity. Due to the requirement of gauge invariance, the relevant quantum states contain strong entanglement between gravity and fermionic degrees of freedom. Interestingly we find that properties and spectra of the observables are nevertheless similar to their counterparts from quantum mechanics. However, there are also new effects. Due to the entanglement between gravity and fermionic degrees of freedom, alignment of quantum spins has consequences for quantized geometry. We sketch a particular effect of this kind that may in principle be observable.
{"title":"Fermion spins in loop quantum gravity","authors":"Refik Mansuroglu, H. Sahlmann","doi":"10.1103/PHYSREVD.103.066016","DOIUrl":"https://doi.org/10.1103/PHYSREVD.103.066016","url":null,"abstract":"We define and study kinematical observables involving fermion spin, such as the total spin of a collection of particles, in loop quantum gravity. Due to the requirement of gauge invariance, the relevant quantum states contain strong entanglement between gravity and fermionic degrees of freedom. Interestingly we find that properties and spectra of the observables are nevertheless similar to their counterparts from quantum mechanics. However, there are also new effects. Due to the entanglement between gravity and fermionic degrees of freedom, alignment of quantum spins has consequences for quantized geometry. We sketch a particular effect of this kind that may in principle be observable.","PeriodicalId":8455,"journal":{"name":"arXiv: General Relativity and Quantum Cosmology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81988086","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}
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