Mindscape 271 | Claudia de Rham on Modifying General Relativity

Patreon: / seanmcarroll
Blog post with audio player, show notes, and transcript: www.preposterousuniverse.com/...
Einstein's theory of general relativity has been our best understanding of gravity for over a century, withstanding a variety of experimental challenges of ever-increasing precision. But we have to be open to the possibility that general relativity -- even at the classical level, aside from any questions of quantum gravity -- isn't the right theory of gravity. Such speculation is motivated by cosmology, where we have a good model of the universe but one with a number of loose ends. Claudia de Rham has been a leader in exploring how gravity could be modified in cosmologically interesting ways, and we discuss the current state of the art as well as future prospects.
Claudia de Rham received her Ph.D. in physics from the University of Cambridge. She is currently a professor of physics and deputy department head at Imperial College, London. She is a Simons Foundation Investigator, winner of the Blavatnik Award, and a member of the American Academy of Arts and Sciences. Her new book is The Beauty of Falling: A Life in Pursuit of Gravity.
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Sean Carroll channel: / seancarroll
#podcast #ideas #science #philosophy #culture

[@sashakindel3600]

I find this one refreshing for how nonjudgmental it is about the merits of different hypotheses. No accusing people looking into other options of being so lost that what they're doing doesn't even qualify as science, or whatever. Just a simple "we haven't ruled this out, so someone should look into it," which seems to me like a healthy attitude to have in science.

[@alevans51]

Profound insight by Claudia de Rahm. Thank you Sean Carroll for bringing her onto your show.

[@vaughnjosh87]

Really annoying monotonous voice and that nervous giggle put me off this one.

[@rumidude]

Well, I am certainly impressed by Claudia de Rham and her general comportment. She exudes knowledge and confidence. It's also a glimpse into what others are doing to figure out the mystery of our universe. One of those cases where I didn't understand yet enjoyed immensely.

[@8pelagic610]

Wow. Lucid, brilliant, exceptional discussion.

[@topcat7365]

Thanks for this Sean - great topic!

[@aden3113]

You should get a camera to film the guests which would really complement the audio.

[@SG-kj2uy]

Super duper interesting episode ❤

[@ottofrank3445]

PERFECT SEAN! JUST PERFECT! MANY THANKS.

[@steliosp1770]

Another excellent episode. Thank you, Sean and Claudia!

[@michaelblacktree]

That was absolutely brilliant! Thank you for giving my brain a workout. 👍

[@kevconn441]

No...please.. It's taken me decades to just get one finger tip on GR...now they are going to change it

[@jessenyokabi4290]

Profound share by Claudia de Rahm. Thank you Sean Carroll for bringing her onto your show. This episode was excellent.

[@vanikaghajanyan7760]

1:13:03 On gravity/inertial induction: “The ds, which is assumed to have the dimension of time, we denote by dт; then the constant k has the dimension Length Mass and in CGS-units is equal to 1, 87.10^ ± 27. See Laue, Die Relativitatstheorie, Bd. II, S. 185. Braunschweig 1921”. Apparently, the following expression takes place: μ(0)ε(0)Gi=1, which means that Gi=с^2 where i is inertial constant, i=1,346*10^28[g/cm]; or k°=1/i=7,429*10^-29[cm/g]: k(Laue)/k°=8π; where k°=r(pl)/m(pl).} Hence, in accordance with the solution of Schwartzchild, the basic formula of QG is derived: ф(G)=(-1/2)[Għ/с]^½ (w)=[Gm(pl)/2c](w)=-[h/4πm(pl)]w=-[w/w(pl)]c^2/2, where ф(G) - is Newtonian gravitational potential, w - the frequency of the quanta of the gravitational field (space-time); the constant Gm(pl)/2c is a quantum of the inertial flow Ф(i) = (½)S(pl)w(pl) = h/4πm(pl) (magnetic flux is quantized: = h/2e, Josephson’s const; and the mechanical and magnetic moments are proportional).Thus, the phenomenon can be interpreted as gravity/inertial induction. Can be tested experimentally in the laboratory at the moment. Addition 0. Expansion is a special kind of motion, and it seems that the Universe is a non-inertial frame of reference that performs variably accelerated motion along a phase trajectory, and thereby creates a phase space. 1.Real gravitational fields are variable in space and time, and we can now talk about the fact that it is possible to generate a gravitational field in a non-inertial frame of reference (|a|=g).That is, finally achieve global (instead of local in GR) compliance with the strong equivalence principle. 2.According to general estimates, this acceleration is: |a|=πcH: the equations of the gravitational field can be arrived at based on the Poisson equation ∆ф=4πGp, and for a weakly curved metric, the time component of the energy-momentum tensor: T(00)=pc^2. Therefore, the Poisson equation can be written as: ∆g(00)=8πGT(00)/c^4, where g(00) is the time component of the metric tensor. This equation is true only in the non-relativistic case, but it is applicable to the case of a homogeneous and isotropic Universe, when Einstein's equations have only solutions with a time-varying space-time metric. Then the energy density of the gravitational field: g^2/8πG=T(00)=pc^2, where the critical density value determining the nature of the model is: p=(3/8π)H^2/G. Hence it follows: g~πcH. And according to the strong equivalence principle: g=|a|=πcH. 3.Then the energy density of the relic radiation, that is, the evolving primary gravitational-inertial field (= space-time): J= g^2/8πG=(ħ/8πc^3)w(relic)^4~1600 quanta/cm^3, which is in order of magnitude consistent with the observational-measured data (about 500 quanta/cm^3).* ----------- *) - w(relic)^2=πw(pl)H, |a|=r(pl)w(relic)^2 =g=πcH, a.Intra-metagalactic gravitational potential: |ф0|=(c^2)/2(√8n')=πGmpl/λ(relic)=[Gm(pl)/2c]w(relic). b.m(pl)w(pl)=8πM(Universe)H; { w(relic)^2=πw(pl)H. c.From Kepler's third law follows: M/t=v^3/G, where M/t=I(G)=[gram•sec^-1] is the gravitational current. In the case of the Universe, I(G)=MH=c^3/8πG (~ the "dark" constant). d.n' =4,28*10^61; w(pl)=(√8n')w(relic)=8πn'H; where H=c/L, L is the length of the phase trajectory. H=1,72*10^-20(sec^-1). e.By the way, it turns out that the universe is 1.6 trillion years old! f.The area of the "crystal sphere": S(universe)~n' λ(relic)^2~n'S(relic). r=2.7*10^29cm, L=2πr. P.S.The inscription on the ancient Roman clock: “More than you think”.

[@brigittegerth6402]

Very interesting facts. I'am a physicist (female) and I am never learnd so much about gravitation. I worked in the Micrososmos of the Microelectronic....13nm-Effects....light observations of Lasers....

[@vanikaghajanyan7760]

@@brigittegerth6402 Thank you. I am not a physicist (a classical guitarist, but once I graduated from the Polytechnic Institute as a constructor/technologist of electronic devices). Perhaps my publications will be of interest to scientific organizations that have the technical means and, since gravity is an urgent area for research, are ready to conduct experiments based on non-standard ideas "for luck". And the proposed experiment is simple and not expensive. What do you recommend? 0.“A purely algebraic theory is required to describe reality." (Einstein, January, 1955). 1.GR was QG? This assumption follows from the Schwarzschild solution and can be tested experimentally in the laboratory at the moment. 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). 2. 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*. 3. As a fundamental theory, GR has the ability with just one parameter: r(G)/r=q to predict, explain new physical effects, and amend already known ones. Photon frequency shift in gravitational field Δw/w(0)=q; the angle of deflection of a photon from a rectilinear propagation path =2q, 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 =3πq, 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). 4. The parameter q is not necessarily a measure of the deviation of the metric from the pseudo-Euclidean one, since in the quantized phase space q=πr/L, where L is the length of the phase path and πr^2=r(G)L. GR/QG predicts a new physical effect: w/w(pl)=q; 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=M/2∆m: system gravity unpacking ratio, n'- the orbit number (n'=0,1,2,3…). a.The constant c^2 / 2w(pl) in the final formula is a quantum of the inertial flow Ф(i) = (½)S(pl)w(pl) = h/4πm(pl) (magnetic flux is quantized: = h/2e, Josephson’s const; and the mechanical and magnetic moments are proportional).Thus, the phenomenon can be interpreted as gravity/inertial induction. b. Obviously, on the horizon [r=r(rG), n'=0] the "door" is closed, however, the quanta [λ=λ(pl)] can go out singly 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[=πr^2/r(G)] is the length of the phase trajectory (of course, the quanta coming through the "window" are also rhythmically restored). c.The phase velocity of evolution v'/π= r(pl)w/π; m(0)=(c/2G)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. The gravitational field is characterized by a spontaneous flow: J*=(v'/π )(1/4π) g^2/G, where v'/π- phase velocity of field evolution. d. 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). e. Accordingly, m=m(pl)/(1+n'/n), where m=ħw/c^2, is the quantum of the full mass: M=n'm [

[@GRUMIAM]

Sean the greatest

[@user-kd2ue8ux1e]

delightful

[@Faustian10]

Anyone have a link to his talk that refers to in the opening few minutes?

[@dirkschwartz1689]

Just search for "Sean Carroll Biggest Ideas talk"

[@zack_120]

11:26 - Sean but you can tap on Antigravity to Defeel gravity - real life confirmed✌️

[@mrrobototoo6663]

Is she related to Georges de Rham, of de Rham cohomology fame?

[@rogerlie4176]

I asked ChatGPT and he seemed confident, but you know... "Claudia de Rham and Georges de Rham are indeed related. Claudia de Rham is the granddaughter of Georges de Rham. Georges de Rham was a Swiss mathematician known for his work in differential geometry and algebraic topology, particularly for his contributions to de Rham cohomology. Claudia de Rham, on the other hand, is a theoretical physicist known for her work in theoretical cosmology and modified gravity theories."

[@user-tq8om7fg2v]

How much is Big Bucks?

[@chrisrecord5625]

I have spent the last week evaluating Einstein's Field Equations and found no obvious flaws. 😉😉I also concluded that gravity is an emergent force subject to change. Case closed

[@adrianhosak734]

I wonder if this modified theory of gravity also has implications concerning dark matter. That would have been an interesting last question!

[@quarkraven]

i feel like i need to "eat my vegetables" suck it up and listen to this precisely because i am so profoundly incredulous that the program of modifying general relativity has promise

[@sonarbangla8711]

The universe whether finite or infinite is defined by Maldacena as a QC function of the unitary evolution of Schrodinger's wave function.

[@thomabow8949]

Sean - would you consider hosting an Astronaut for Mindscape?

[@trevorcrowley5748]

Believe Dr de Rham trained to be an Astronaut. Very brave

[@brigittegerth6402]

She has started the testlevel. And she was one of 40 persons at the end. I read there book. But one medical test with tuberculosis bacteria inside the body ended the dream.

[@brianb.7435]

Very interesting. I wished that she would talk slower, would have been easier to listen to.

[@LuciFeric137]

You ok? I always hear police sirens in the background. Another very interesting segment.

[@wmpx34]

You ever watch The Wire lol?

[@dreamlandskribbl]

I've noticed how all of these comments are all positive but I don't like this show, not because of anything the show has or anything like that but because I'm looking for a series about some person in a place called 'the deepest part of the mindscape and I've had to scroll through hundreds of these podcasts for days and I feel like if it didn't excist I would have found this series by now.

[@topos100]

More mainstream Mis-direction...

[@Cytropical-dk7wp]

Third comment

[@CurtOntheRadio]

One of the least understandable episodes. :D

[@brigittegerth6402]

We are at the beginning of a deeper understanding of the cosmos. We some images to understand. Our brain can only do little with mathematcs equations. But that is the realistic world of a theoretical physicist.

[@robertfontaine3650]

The desire for quantized gravity and gravitons is a lot like the religious belief in string theory. There is no particular reason for merging gravity into quantum mechanics but the math is pretty.

[@steve112285]

One reason we need a theory that combines them is that there are circumstances where both are relevant, so we can't currently predict what happens. Sean gives the examples of the interior of black holes, or the beginning of the universe. Short distances so quantum mechanics is needed, high mass-energy so general relativity is needed.

[@dmitryshusterman9494]

It's extremely painful listening to her. She never gets to complete her point. It's too bad.

[@WhataMensch]

Sean will you speak out on the war crimes in gaza on the next podcast please. As an American silence is not an option

[@OptimusVlad]

I hope he doesn't. Not every aspect of society need be stuffed with other people's political opinions. If you want to talk politics, go to a political forum. Keep science channel focused on science.

[@ajsmith7619]

Thanks. I was trying to say something similar.

[@WhataMensch]

@@ajsmith7619 Excellent. We need to speak out now as the situation is worse day by day

[@WhataMensch]

@@OptimusVlad Did you ever take a history class and hear about the silence of academics and institutions during the Shoah? All I am asking for is a statement of support for antigenocide from this man who I respect and has a large voice.

[@WhataMensch]

@@jeffreyblue627 I dont care about blood feuds. I care about the current arming of a rogue state in violation of the highest court in the worlds orders to stop the mass killing

[@kcinkg]

Gravitons…not a thing.

[@brigittegerth6402]

Graviton sounds good. If you give something a name, you can research it. Existence yes or no? Will it show up at some point?

[@kcinkg]

@@brigittegerth6402 so does truth in advertising