arXiv subjects

Jiayin Shen

Publications and source records attributed to Jiayin Shen.

3 recordsLinked to original sources

arXiv2020

The Uplifting of AdS Type to Quintessence Like Potential Induced by Frozen Large Scale Lorentz Violation

The quintessence-like potential of vacuum energy can meet the requirement from both quantum gravity and the accelerating expansion of the universe. The anti-de Sitter vacuum in string theory has to be lifted to the meta-stable de Sitter vacuum with positive vacuum energy density to explain the accelerating expansion of the universe. Based on the possible large scale Lorentz violation, we define an effective cosmological constant which depends not only on the bare cosmological constant but also on the Lorentz violation effect. We find the evolution of the effective cosmological constant exhibits the behavior of quintessence potential when the bare cosmological constant is from string landscape in contrary to the existence of local minimum during evolution while the bare cosmological constant is supplied by the swampland. The critical value of bare cosmological constant is approximately zero for the behavior transition. The frozen large scale Lorentz violation can uplift the AdS vacua to an effective quintessence-like one in this sense.

hep-th↗

arXiv2018

Large Scale Lorentz Violation Gravity and Dark Energy

The accelerating expansion of universe can be described by the non-zero cosmological constant or the dark energy. However, the origin of the dark energy remains a mystery of modern physics. The local Lorentz invariance is the most exact symmetry of the Nature on the one hand, but all quantum gravity theories predict Lorentz violation on the other hand. The local Lorentz violation induced by the quantum gravity at the very early universe may be transformed into large scale by inflation. Combining the low-$l$ anomalies of the CMB spectrum, we propose that the local Lorentz invariance may be broken at the large scale. We construct the effective gravity at the cosmic scale with a local $SO(3)$ symmetry. The theory exhibits non-trivial contortion distribution even with scalar matter source. The FRW like solution of the theory is analyzed and the contortion distribution contributes a dark energy like effect which is responsible for the accelerating expansion of the universe. It reveals that the dark energy may be the remnants of quantum gravity in this sense.

gr-qc↗

arXiv2018

Understanding the electromagnetic 4-potential in the tetrad bundle

Separation of the spin and orbital angular momenta of the electromagnetic field has been discussed frequently in recent years. The spin and orbital angular momenta cannot be made simultaneously gauge invariant and Lorentz covariant and are not conserved separately. After analyzing the source of the problem, we find that the electromagnetic 4-potential depends on the local reference frame instead of the global reference frame. The transformation of the local reference frame is the intrinsic degree of freedom of the electromagnetic field. Therefore, considering only the Lorentz transformation of the global reference frame and neglecting the Lorentz transformation of the local reference frame may lead to the noncovariance of the electromagnetic 4-potential. Accordingly, we redescribe these difficulties of the electromagnetic field from the perspective of quantum field theory. By using the behavior of the electromagnetic 4-potential that satisfies the Coulomb gauge in Lorentz coordinate transformation, we can construct the electromagnetic vector in the tetrad bundle. The various physical quantities that are induced by this electromagnetic vector satisfy Lorentz covariance in the tetrad bundle. This electromagnetic vector, which is projected onto space-time, is an electromagnetic 4-potential that satisfies the Coulomb gauge; thus, the electromagnetic vector is gauge invariant.

physics.class-ph↗