Paul Steinhardt - Big Bang or Big Bounce?

In this video series entitled "Conversations at Niels Bohr's Office" Johan Samsing from the Niels Bohr Institute presents conversations with some of the most influential physicists and thinkers of over time on topics related to the fundamental physics of our Universe.
Each episode is recorded at the historical Niels Bohr's Office and based on one long take with no script, with the intention of creating a more natural conversation about whatever topics the guest wants to highlight.
6. Episode: "Does our Universe hints for a Big Bounce instead of a Big Bang?"
Paul Steinhardt is an American physicist, known for his groundbreaking work on the origin, evolution and future of the universe, as well as his exploration of a new form of matter, known as quasicrystals. He has been faculty at Princeton University since the Fall of 1998, and he co-founded the Princeton Center for Theoretical Science and served as its Director from 2007 to 2019. Paul Steinhardt has received numerous prices including the Niels Bohr Institute Medal of Honour in 2020.

[@chrisdiver6224]

Very heartening that the slow contractions universal smoother comes out of general relativity.

[@draxiedru]

I’m a lay person with a life long interest in cosmology so forgive me if I sound silly but it sounds like the description for a Groundhog Day universe. How can all the expansions after the “bounce” create something different if the ingredients don’t change because the goal is to always maintain universal smoothness.

[@mattmiller4917]

Worthwhile video, and you have a new subscriber. However, I do wish you had asked about pushback on his theory. In this video, Steinhardt makes it sound like cosmologists are pretty evenly split between his view and inflation, but in reality, most cosmologists are still invested in inflation theory, and "slow inflation" is a radical new idea with very few adherents. I personally find it exciting, but people far smarter than me don't give it the time of day. So what do Alan Guth and other "hardcore inflationists" think about Steinhardt's ideas? What is their response to his criticisms of inflation? This is what I would like to know now.
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[@DrakeLarson-js9px]

Between the two: My vote is that the "Big Bounce" is best ... But inversion physics - and teaching more about tensor analysis would be useful for physics majors...(Again: Edward Teller's videos about his attending Einstein lectures: Summary, Einstein's Special Relativity is an A+... while General Relativity??!(huh?!)? - Teller's videos about attending a lecture by Einstein in the 20s should be mandatory for ALL physics majors. )

[@vanikaghajanyan7760]

27:00. : "It can be convincingly proved that reality cannot be represented by a continuous field at all. It seems to follow from quantum phenomena that a finite system with finite energy can be completely described by a finite set of numbers - quantum numbers... A purely algebraic theory is required to describe reality." (Einstein, January, 1955).
Maybe GR was QG…
“The geometry of space in general relativity theory turned out to be another field, therefore the geometry of space in GR is almost the same as the gravitational field.” (Smolin).
However apparently, the gravitational field is space-time in the Planck system: F(G)/F(e)=Gm(pl)^2/e^2=1/α, that is, gravity~strong interaction*.
This assumption follows from the Schwarzschild solution: the gravitational radius (or Schwarzschild radius) is a characteristic radius defined for any physical body with mass: r(G)=2GM/c^2
Consequently: 2E(0)/r(G)=F(pl)=c^4/G=ε(pl)/r(pl): with indicating the mutual quantization of the mass (energy) and space-time: m(0)//m(pl)=r(G)/2r(pl)=n,where n-total number of quanta of the system; the tension vector flux: n=[(1/4π)(Gћc)^-½]gS ( const for all orbits of the system: n=0,1,2,3....).
Moreover, the parameter r(0)=r(G)-r(pl)=(2n-1)r(pl), defining the interval of the formation of the system, at n=0, when r=r(G)=0 (for example, the state of the "universe" before the Big Bang) turns out to be a quite definite quantity: r(0)=-r(pl).
In the area [(-rpl) - 0 - (+rpl)] there is an implementation of external forces, "distance": (-rpl)+(+rpl)=0 (≠2rpl).
On the Kruskal diagram of the hyperbole r=0 corresponds to the true Schwarzschild feature, the features V and VI are not even covered by the global (R, T)- space-time and correspond to the "absolute" vacuum; then the singular areas above and below the hyperbolas r=0 can be formally treated as the energy source (external forces).
That is, the frightening "true singularity" is actually a superconducting heterotrophic "window" between the proto-universe (the source) and physical bodies**.
P.P.S.
As a fundamental theory, GR has the ability with just one parameter: r(G)/r=k to predict, explain new physical effects, and amend already known ones.
Photon frequency shift in gravitational field Δw/w(0)=k; the angle of deflection of a photon from a rectilinear propagation path =2k, the Newtonian orbit of the planet shifts forward in its plane: during one revolution, a certain point of the orbit is shifted by an angle =3πk, for a circular orbit (eccentricity е=0); in the case of an elliptical orbit - for example, for perihelion displacement, the last expression must be divided by (1-e^2).
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*) - GR predicts a new physical effect: w/w(pl)=k; expression for gravitational radiation from a test body.
This is amenable to physical examination in laboratory conditions at present.
**) - From this, generally, from Einstein's equations, where the constant c^4/G=F(pl), one can obtain a quantum expression (as vibration field) for the gravitational potential: ф(G)=(-1/2)[Għ/с]^½ (w)=-[h/4πm(pl)]w.
Final formula:ф(G)=-[w/w(pl)]c^2/2, where ф(G) - is Newtonian gravitational potential, r(n')=nλ/π=(n+n')2r(pl)l , the corresponding orbital radius, w - the frequency of the quanta of the gravitational field (space-time); - obviously, the quanta of the field are themselves quantized: λ=(1+n'/n)λ(pl) = 2πc/w, where n'/n - system gravity unpacking ratio, n'- the orbit number (n'=0,1,2,3…).
Obviously, on the horizon [r=r(rG), n'=0] the "door" is closed, however, the quanta [λ=λ(pl)] can go out singly through the "keyhole" and form the first and all subsequent half-orbits (n'=1,2, 3 ...) during the time t(0)=r/c=2nт, where т=1/w, т=((1+n'/n)т(pl), spending part of their energy on it each time. And it is this mechanism that provides the step-by-step formation of a variable gravitational field: variably accelerated expansion of spacetime as a phase space: |a|=g=πc^2/L, where L is the length of the phase trajectory (of course, the quanta coming through the "window" are also rhythmically restored).
The phase velocity of evolution v'/π= r(pl)w/π; m(0)=(c/G)rv', where v'=v^2/c.
The angular momentum: L(p)=|pr|=n^2ћ [const for all orbits of the system; at n=1: L(p)=ћ] and moment of power: M(F)=dL(p)/dt(0)=nћw/2=-E(G)=E*, where t(0)=r/c, E*- energy of self-action.
According to GR / QG, gravitational field [E(G)=-E*] is characterized by a spontaneous flow: J*=(v'/π )(1/4π) g^2/G, where v'/π- phase velocity of field evolution.
Entropy (here: a measure of diversity/variety, not ugliness/disorder) of the system: S=πε(pl)r(t)=(n+n')k, where k is the Boltzmann constant. Obviously, on the horizon entropy=min and with fundamental irreversibility, information is preserved (+ evolves, accumulates).
Accordingly, m=m(pl)/(1+n'/n), where m=ħw/c^2, is the quantum of the full mass: M=n'm [