Barbero-Immirzi field in canonical formalism of pure gravity

Calcagni, Gianluca; Mercuri, Simone

doi:10.1103/physrevd.79.084004

Cited by 98 publications

(149 citation statements)

References 52 publications

Supporting

Mentioning

144

Contrasting

Order By: Relevance

Section: Introductionmentioning

confidence: 79%

“…This anomaly leads to the inclusion of the Pontryagin density in an effective fermionic action [7]. Similarly, it has been recently found that LQG also leads to CS modified gravity when the Barbero-Immirzi parameter is promoted to a pseudo-scalar field in the presence of fermions [8,9,10,11,12].The signature of CS modified gravity is the enhancement of gravitational parity asymmetry, which in particular leads to frame-dragging modifications [13,14,15]. In GR, the gravitomagnetic sector of the metric couples to the spin and the orbital angular momentum of gravitating systems, leading to corrections in their orbital evolution, such as precession of the orbital plane.…”

mentioning

confidence: 84%

See 1 more Smart Citation

Double-binary-pulsar test of Chern-Simons modified gravity

2009

View full text Add to dashboard Cite

Chern-Simons modified gravity is a string-theory and loop-quantum-gravity inspired effective theory that modifies General Relativity by adding a parity-violating Pontryagin density to the Einstein-Hilbert action multiplied by a coupling scalar. We strongly constrain non-dynamical ChernSimons modified gravity with a timelike Chern-Simons scalar through observations of the double binary pulsar PSR J0737 − 3039A/B. We first calculate Chern-Simons corrections to the orbital evolution of binary systems. We find that the ratio of the correction to periastron precession to the general relativistic prediction scales quadratically with the semi-major axis and inversely with the square of the object's radius. Binary pulsar systems are thus ideal to test this theory, since periastron precession can be measured with sub-degree accuracies and the semi-major axis is millions of times larger than the stellar radius. Using data from PSR J0737 − 3039A/B we dramatically constrain the non-dynamical Chern-Simons coupling to MCS := 1/|θ| > 33 meV, approximately a hundred billion times better than current Solar System tests. I. INTRODUCTIONString theory is an intricate web of mathematically beautiful hypothesis that promises to unify all forces of nature. General Relativity (GR) is expected to be its low-energy limit with possible higher-order curvature corrections. To date, however, string theory remains intrinsically difficult to test experimentally, because these curvature-corrections are believed to be perturbatively Planck suppressed. Dynamical situations with large spacetime curvature could lead to non-linear couplings and enhance such curvature corrections to a constrainable realm.One such curvature correction is the parity-violating Pontryagin density, which in addition to the EinsteinHilbert term defines an effective theory: Chern-Simons (CS) modified gravity [1]. In four dimensions, this density is a topological term that does not contribute to the field equations, unless its coupling is non-constant or promoted to a scalar field [2]. From a string theoretical standpoint, the Pontryagin correction is inescapable, if one is to have a mathematically consistent theory that is anomaly-free [3,4,5]. From an experimental standpoint, the search for the breakage of fundamental symmetries can provide hints that can guide theorist toward the correct ultraviolet completion of GR.CS modified gravity is also motivated from the standard model of elementary particles and from Loop Quantum Gravity (LQG). For example, in particle physics, we know that an asymmetry in the number of left-and right-handed fermions forces the fermion number current to be anomalous, in analogy to the triangle anomaly [6]. This anomaly leads to the inclusion of the Pontryagin density in an effective fermionic action [7]. Similarly, it has been recently found that LQG also leads to CS modified gravity when the Barbero-Immirzi parameter is promoted to a pseudo-scalar field in the presence of fermions [8,9,10,11,12].The signature of CS modified gravity is the enhan...

show abstract

Section: Introductionmentioning

confidence: 79%

mentioning

confidence: 84%

Double-binary-pulsar test of Chern-Simons modified gravity

2009

View full text Add to dashboard Cite

show abstract

“…The Pontryagin term in the action is involved in anomaly cancellation [30]. Such a term also appears naturally in heterotic superstring theory [30][31][32] and loop quantum gravity [33][34][35]. Dynamical CS gravity also arises naturally in effective field theories of inflation [36].…”

Section: Introductionmentioning

confidence: 99%

Isolated and binary neutron stars in dynamical Chern-Simons gravity

et al. 2013

View full text Add to dashboard Cite

In Ref.[1], the Chern-Simons correction to the osculating orbital elements due to the dipole-dipole interaction for the scalar field was derived in Eq. (130) by integrating out the interaction Lagrangian, which was taken to be the kinetic term for the scalar field [Eq. (122) in [1]], using the scalar field solution. However, such kinetic term only leads to the left-hand side of the evolution equation for the scalar field, i.e.where J is the effective source term of the scalar field equation [2]. In order to obtain the correct interaction Lagrangian, one also needs to include the source term (L source ) that reproduces the right-hand side of the above evolution equation. The Lagrangian density for such an additional term is given by −ϑJ. Therefore, Eq. (126) needs to be changed towhere L source,int is the interaction part of the source term Lagrangian density. Notice that, by accounting for such additional term, the sign of the interaction Lagrangian now flips. This means that the sign in Eqs. (127), (129) and (130) needs to be reversed. The results in Sec. IX B are unaffected since we have neglected contribution from the dipole-dipole interaction because the spin of the secondary pulsar in the double binary pulsar is much smaller than that of the primary. We also report errors in App. B of [1]. In this appendix, we calculated dissipative corrections to the energy and angular momentum energy flux emitted from neutron star binaries based on calculations in [2]. However, some terms in the perturbed scalar and metric field equations were not properly accounted for in [2]. Taking these terms into account, we found that corrections to the gravitational energy and angular momentum flux due to metric perturbations enter at third post-Newtonian order relative to general relativity, which is of 1 post-Newtonian order higher than the effect due to the scalar field. Therefore, Apps. B.1.b and B.2.b in [1] are now irrelevant. We discuss this in more detail in [3].On the other hand, the scalar energy flux in App. B.1.a is affected as follows. First, the far-zone solution for the scalar field in Eq. (B3) becomesThen, the scalar energy flux in Eqs. (B5) and (B6) becomesrespectively. Finally, Eq. (B8) is corrected to T. Tanaka, Phys. Rev., D85, 064022 (2012), arXiv:1110.5950 [gr-qc].[3] K. Yagi, L. C. Stein, N. Yunes, and T. Tanaka, Phys. Rev., D93, 029902 (2016D93, 029902 ( ), arXiv:1110. We study isolated and binary neutron stars in dynamical Chern-Simons gravity. This theory modifies the Einstein-Hilbert action through the introduction of a dynamical scalar field coupled to the Pontryagin density. We here treat this theory as an effective model, working to leading order in the Chern-Simons coupling. We first construct isolated neutron star solutions in the slow-rotation expansion to quadratic order in spin. We find that isolated neutron stars acquire a scalar dipole charge that corrects its spin angular momentum to linear order in spin and corrects its mass and quadrupole moment to quadratic order in spin, as measured by ...

show abstract

“…However, when torsion is present (for instance, when it is generated by fermions or a spacetime-dependent Barbero-Immirzi field [18][19][20][21][22]), it is natural to include it explicitly in the fundamental action, so that the Holst term is completed by a torsion-torsion piece to form the Nieh-Yan invariant [17,23]. There are several other reasons why to prefer the latter alternative.…”

Section: Ij µmentioning

confidence: 99%

Erratum: Cosmological Bardeen-Cooper-Schrieffer condensate as dark energy [Phys. Rev. D81, 043511 (2010)]

Alexander¹,

Biswas²,

Calcagni³

2010

Phys. Rev. D

Self Cite

View full text Add to dashboard Cite

We argue that the occurrence of late-time acceleration can conveniently be described by firstorder general relativity covariantly coupled to fermions. Dark energy arises as a Bardeen-CooperSchrieffer condensate of fermions which forms in the early universe. At late times, the gap and chemical potential evolve to have an equation of state with effective negative pressure, thus naturally leading to acceleration.

show abstract

Barbero-Immirzi field in canonical formalism of pure gravity

Cited by 98 publications

References 52 publications

Double-binary-pulsar test of Chern-Simons modified gravity

Double-binary-pulsar test of Chern-Simons modified gravity

Isolated and binary neutron stars in dynamical Chern-Simons gravity

Erratum: Cosmological Bardeen-Cooper-Schrieffer condensate as dark energy [Phys. Rev. D81, 043511 (2010)]

Contact Info

Product

Resources

About