"the gravitational
field.
We compute the
particle production in a time-dependent gravitational
field induced by an expanding mass shell"
I have made two intuitive leaps that I have not yet been able to prove rigorously, but I bet will prove correct.
1) The observer-dependent dark energy future event horizon is the Wheeler-Feynman total absorber. This needs the hologram Ansatz that the interior 3D + 1 bulk is a retrocausal hologram image of the 2D + 1 surrounding event horizon surface where our future light cone intersects it.
2) Roger Penrose's "spin frame" has two QUBIT spinors, which in the case of the null light cone tetrads of Einstein's gravity field, l, n, m & m* are advanced and retarded spinors with support on the past and future local light cones respectively. Note that the usual tetrads where the time component is along the world line of the observer-detector and a spacelike triad, consist in form of the Bell pair states of spinor QUBITs used all the time in quantum information/computer theory. This is why I use Wheeler's "IT FROM (Q) BIT."
Similarly, time reverse particle absorption.
~ = photon
X = gravity field fluctuation
the classical stretching of the photon wavelength in accelerating expanding space can be pictured at the quantum level as a sequence of photon absorptions and re-emissions by the gravity field whose statistical mean value obeys the Einstein GR prediction.
i.e. "Feynman diagram"
~X~X~X~ .....
A note on tetrads & Penrose's spinor QUBITs
In an LIF we have e^I for an "observer" and e^U in a locally coincident accelerating LNIF.
e^I = e^IUe^U
Note that these are Cartan 1-forms not 4-vector components - that's why I use CAPS, small letters i, u etc. are for the usual tensor indices.
Since Newton's gravity field ~ guv,w is eliminated at the origin of the LIF, the e^I are the same as what they are for inertial frames in special relativity (EEP). However,
e^U(LNIF) = e^U(LIF) + B^U(LNIF)
B^U(LNIF) is Paul Hill's "acceleration field" analogous to the electromagnetic vector potential A for the U1 group. However, B^U(LNIF) is the local gauge compensating potential for the T4 translation group.
A = Audx^u Cartan 1-form
B^U(LNIF) = B^Uudx^u Cartan 1-form
i.e. a set of four 1-forms like a Yang-Mills field with an internal charge.
The EEP says that the
universal minimal coupling of the EM field to the gravity field for the accelerating LNIF observer is simply to replace all LIF electromagnetic potential Cartan 1-forms A(LIF) by
A(LNIF) = A(LIF) + B^U(LNIF)PUA(LIF) Cartan 1-forms
P^U are the 4-momentum generators of the T4 group.
before constructing the dynamical action S for the Feynman amplitudes e^iS.
So it's obvious it looks like a direct coupling of spin 1 (Lorentz group) GMD with EM fields.
Rovelli in Ch II of his Quantum Gravity gives details for spinor & Yang-Mills matter fields.
Next IT FROM QUBIT - in the special case of the NULL LIGHT CONE tetrads, for the GMD field
B^Uu = (Newman-Penrose coefficients)^Uu^j^k(Advanced QUBIT spinor)j(Retarded QUBIT)k
(using quasi Penrose abstract index notation)
This is an entangled quantum pair state on RHS of QUBITs.
