Instantaneous vacuum for Dirac fields with a Yukawa interaction in cosmological space-times

Adiabatic regularization with a Yukawa interaction

We extend the adiabatic regularization method for an expanding universe to include the Yukawa interaction between quantized Dirac fermions and a homogeneous background scalar field. We give explicit expressions for the renormalized expectation values of the stress-energy tensor $\langle T_{μν} \rangle$ and the bilinear $\langle \barψψ\rangle$ in a spatially flat FLRW spacetime. These are basic ingredients in the semiclassical field equations of fermionic matter in curved spacetime interacting with a background scalar field. The ultraviolet subtracting terms of the adiabatic regularization can …

Renormalization, running couplings and decoupling for the Yukawa model in curved spacetime

The decoupling of heavy fields as required by the Appelquist-Carazzone theorem plays a fundamental role in the construction of any effective field theory. However, it is not a trivial task to implement a renormalization prescription that produces the expected decoupling of massive fields, and it is even more difficult in curved spacetime. Focused on this idea, we consider the renormalization of the one-loop effective action for the Yukawa interaction with a background scalar field in curved space. We compute the beta functions within a generalized DeWitt-Schwinger subtraction procedure and dis…

Quantum corrected power spectra of massless minimally coupled scalars during inflation: Effects of Yukawa coupling versus quartic self-interaction

We, in the first part, contemplate a massless minimally coupled scalar which is Yukawa-coupled to a massless Dirac fermion in a locally de Sitter background of an inflating spacetime. We compute the scalar's quantum corrected mode function, power spectrum, spectral index and the running of the spectral index at one-loop order. We find that the spectrum is slightly blue-tilted; hence, the amplitudes of fluctuations grow slightly toward the smaller scales. Then, in the second part, we apply the computation method used in the first part to a massless minimally coupled scalar with a quartic self-i…

Adiabatic expansions for Dirac fields, renormalization, and anomalies

We introduce an iterative method to univocally determine the adiabatic expansion of the modes of Dirac fields in spatially homogeneous external backgrounds. We overcome the ambiguities found in previous studies and use this new procedure to improve the adiabatic regularization/renormalization scheme. We provide details on the application of the method for Dirac fields living in a four-dimensional Friedmann-Lemaitre-Robertson-Walker spacetime with a Yukawa coupling to an external scalar field. We check the consistency of our proposal by working out the conformal anomaly. We also analyze a two-d…

费米子暴胀宇宙学中 Yukawa 相互作用的信号

Signals from Fermionic inflationary cosmology with Yukawa interaction

本研究探讨了 Dirac 场与暴胀子通过 Yukawa 相互作用的暴胀模型，发现强耦合时张量-标量比被显著抑制，弱耦合时与标准冷暴胀一致，为观测提供了新信号。

The renormalized locally covariant Dirac field

The definition of the locally covariant Dirac field is adapted such that it may be charged under a gauge group and in the presence of generic gauge and Yukawa background fields. We construct renormalized Wick powers and time-ordered products. It is shown that the Wick powers may be defined such that the current and the stress-energy tensor are conserved, and the remaining ambiguity is characterized. We sketch a variant of the background field method that can be used to determine the renormalization group flow at the one loop level from the nontrivial scaling of Wick powers.

Instantaneous Action at a Distance in a Holistic Universe

The early work of Lorentz, Abraham and others, evolved through the work of Fokker, Dirac and others to ultimately culminate in the Feynman- Wheeler direct action at a distance theory. However this theory has encountered certain conceptual difficulties like non-locality in time, self force of the electron, pre acceleration and the perfect absorption condition of Feynman and Wheeler, that is the instantaneous action of the remaining charges in the universe on the charge in question. More recently, Hoyle and Narlikar have resurrected this theory, but within the context of a Steady State or Quasi …

On radiation reaction and the Abraham-Lorentz-Dirac equation

It is underlined that the Lienard-Wiechert solutions indicate that after the external force is instantly removed from a small charged particle, the field in its close neighborhood becomes a Lorentz boosted Coulomb field. It suggests that the force of the self-field on the particle should instantaneously vanish after a sudden removal of the external force. A minimal modification of Abraham-Lorentz-Dirac equation is searched seeking to implement this property. A term assuring this behavior is added to the equation by maintaining Lorentz covariance and vanishing scalar product with the four-veloc…

赝标量汤川耦合在费米子预热过程中诱导的螺旋不对称性

Pseudoscalar Yukawa Coupling Induced Helical Asymmetry in Fermionic Preheating

研究通过引入特定模型研究费米子预热时的螺旋不对称性，利用赝标量汤川机制，采用WKB方法计算博戈留波夫系数跃迁关系，发现赝质量改变高斯分布，实部提高螺旋态数密度，结论获数值结果验证。