Causal Sets : The quantum theory that predicted dark energy

Forum Moderator

What if the key to understanding dark energy was predicted decades ago? This video explores Causal Set Theory, a bold approach to quantum gravity that reimagines spacetime as fundamentally discrete—and may offer surprising insights into the accelerating universe, fine tuning the Big Bang, black holes and more Featuring leading theorists such as Rafael Sorkin, Yasaman Yazdi, Fay Dowker, Sumati Surya, and Niayesh Afshordi, we dive into the origins, predictions, and implications of this fascinating theory.

Keywords: Causal Sets, Quantum Gravity, Dark Energy, Cosmology,

Ethan

This is such a helpful overview of an underappreciated and deeply important branch of Physics. The idea that dynamics emerge from a more discrete underlying structure is powerful. Sorkins willinness to strip things away and start from a humbler set of inputs is inspiring. I am curious to know if Sorkin or others working on Causl Sets have been influenced by the work of G. Spencer Brown. I feel his book Laws of Form raises interesting foundationsal questions that im working on tracking into Physics - specificaly the idea that there is a cost required to maintain distinctions.

Lorraine Ford

Ethan
Just how much naïve woo-woo nonsense can we continue to put up with?

Dynamics/ movement does not emerge.

Physicists knew that years ago.

And now, the age of computing and AIs has comprehensively shown that no set of mathematical symbols that are written on a page can ever represent a complete or self-sufficient or moving system.

The age of computing and AIs has comprehensively shown that algorithmic/ logical connective symbols (like IF, AND, OR, IS TRUE, and THEN) are also needed, if you want to represent a dynamic/ moving mathematical system.

And then you have to say: what necessary aspects of the real-world world moving mathematical system do these algorithmic/ logical connective symbols represent?

Lorraine Ford

The symbols on the mathematician’s page or blackboard didn’t generate themselves, and the symbols don’t move themselves.

I'm saying that there is no mathematics without the mathematician, where the “mathematician” is any part of the mathematics that:

Recognises the mathematical situation represented by the symbols on the page or blackboard, and
Mentally or physically creates or moves the symbols on the page or blackboard in response to this recognition of the mathematical situation.

This knowledge/ consciousness of the mathematical symbols, and this moving of the mathematical symbols, are totally separate aspects of the mathematics to the symbols themselves.

In fact, the ONLY model we have for a real-world mathematical system is mathematics itself, which has the abovementioned 3 aspects:

The symbols
Something that is aware of the symbols
Something that moves the symbols.

Claudio Marchesan

The theory presented in the podcast is truly fascinating and arouses interest, but its application to dark energy may still be premature. Before discussing cosmic acceleration from any theoretical angle — discrete or continuous — perhaps we should first ask a more basic question: what is the role of entropy and reversibility in a cosmological model?

A theory of dark energy cannot avoid these questions. Maybe they are the real starting point.

Dark energy and physical processes: is reversibility a necessary condition for entropy conservation?

Isolated systems. While reversible processes imply entropy conservation, the converse does not necessarily hold in the FLRW framework.
In FLRW, the presence of dark energy does not modify the formal conservation of comoving entropy, because this conservation law follows from the perfect fluid approximation and from the kinematic nature of the expansion. Dark energy affects the background dynamics through the Friedmann equations, but it does not interact with the photon gas; therefore, the CMB remains collisionless and out of equilibrium, yet still formally isentropic within the FLRW description. This shows that entropy conservation in FLRW is not tied to thermodynamic equilibrium, but to the structural assumptions of the model.

Thermodynamic implications. Dark energy and the isoentropic evolution of the CMB are in fact inseparably linked by the FLRW assumptions themselves. In the presence of dark energy, the expansion of the CMB is thermodynamically irreversible, despite the conservation of comoving entropy, because the loss of photon energy through cosmological redshift cannot be reversed by any physical process.
This contrast raises the broader question of whether reversibility is a necessary condition for entropy conservation in the presence of dark energy. In a universe dominated by dark energy, the comoving entropy of the CMB can remain conserved even though the accelerated expansion cannot be interpreted as a reversible thermodynamic process, because the conservation arises from the cosmological dynamics rather than from thermodynamic reversibility.

Lorraine Ford

It’s a case of “can’t see the forest for the trees”.

It is seemingly all too easy to become bogged down by the particulars of energy and forces and time and space.

But when the physics of the world is represented by equations, numbers, and category symbols, we are already taking a higher, meta perspective on the world.

And it is only from this meta perspective that it is possible to notice that all the equations, numbers, and category symbols can’t ever explain why the numbers would ever move, except perhaps as a result of other number movement which itself can’t be explained.

From the meta perspective, the equations, numbers, and category symbols on the page or blackboard can’t explain why the world started to move, or why the world continues to move.

From the meta perspective, movement necessarily involves a number-jump and number assignment intervention, an intervention that can’t be attributed to the equations, numbers, and categories.

The meta perspective shows that intervention (presumably by small parts of the system) is the only cause; the rest is effect.

Lorraine Ford

Lorraine Ford
“Causality” and “Causal Sets” are misnomers because they are all about effect, not about cause.

Actual cause is an intervention in the system (seemingly BY the small parts of the system).

But all such interventions can only have a limited effect on the system, and the real-world moving mathematical system would soon grind to a halt unless interventions were continually made (seemingly by the small parts of the system).

The categories, relationships and numbers that describe aspects of the real-world moving mathematical system have no ability to cause anything all by themselves.

But this fact about the nature of mathematical systems conflicts with a set of beliefs about the nature of the world:

It has seemingly always been the case that the facts conflict with the belief systems.

marcovici alexandru

@Claudio Marchesan , i'm bugged by this questions before i let them sink in i must say that

personally i'm a highly talkative person iv'e looked at how mathematicians developed their style of comunication to handle large strcutures i definitely i have much more to learn, on my undecicompred essay contest i've tried to squeeze all the references in four pages the font was becoming unreadable so i must have mentioned causal sets
i've read all the former earlier arxiv blog articles when it started they must have also linked an article about causal sets
and many mathematicians blogs like for example tim gowers , terry tao and others

(i have written an letter in 2020 with the intent to send it to FQXI with more obvious references like richard feynman
on a printed pagination pre-version)

what is paper made from this days? try to imagine how the rain drops go trough

anyway ,
going back/returning to causal sets :
yes i'm not sure of anything these days however ,algebra , logic, some calculations...

marcovici alexandru

returning to paper , what is a book ?
these days the operating systems have transitons between tabs windows
for linux xmonad ive tried desktop interface that automaticallly placed all the workspace minimising space borders windows on the other hand there was a flipper rolled files like in a folder drawer
do you preferer to scroll pages or to have them sudden appearing

apparently a books gives not many options , and they have for default the paper properties that are abstracted and ignored there are certain optical illusions that can be used to write or other types of binding , looking trough the glasses of a product designer books are amazing and they still have huge potential and they can catch on with the digital interfaces .

returning to universe and entropy i have not finished yet watching the entire video

universe stories imagination , beliefs are conveyed and expressed trough various mediums that build on the previous developments i think is important to understand and experiments with the limits and constraints of those mediums

ICCI the international cryosphere climate initiative has pre-released 'a paper'

Arctic sea-ice ridges are biomass hotspots harboring
diverse microbial communities

with 32 authors , lets say i'm one of those authors, do you want to talk with me about the article? you must prove that you have read it carefully ,how can you draw each word , this may take to much time, or can you read it out loud and record a message , but than i must take my time and have patience to listen to your message ,
we are here 32 authors, to prove that this work is well justified and your time is well spent if you read it carefully

one more time i must say that i have little to no experience how the communication happen between scientists i try to imagine various scenario, of communication between different agents
the fact that one can write with BOLD or other special effects is a sign that people actually use those instruments that's why they have been invented , just because i have not seen it in a communication with me does not mean that they dont exist between other people .

humans are in between scales not to little not to large maybe is wishful approach maybe there are some little things that matter on the large scale or vice versa , the scale separation is consciously ,causally questioned here.

mathematics gives certainty, however in the last 15 years i've looked for variation generalisations to try to have a broad image of math and science , from not being able to solve integral by hand to solve a simple physics problem (i'm stil a beginner in the field) or differential equation for that matter) ive tried to look at evrytng else beside this

btw there are also diferentiointegrals equations
how do you take some data reasons and arrive at certain result

what other new qualities can be looked of this sequential receipts, did play dough inspired the apparition/discovery of automorphisms?
imagine the letters in an equation being taken away doing some new thing than replaced in the same equation

Claudio Marchesan

Thanks for sharing your thoughts — I can see you’ve explored many different sources and perspectives, from mathematicians’ blogs to early discussions on causal sets. It’s a rich background, and it makes sense that these ideas are still resonating with you.

Causal Set Theory is indeed fascinating, and it opens many conceptual doors. But when it comes to dark energy, I feel that applying it directly may still be premature. Before connecting any theoretical framework — discrete or continuous — to cosmic acceleration, we should clarify something more basic: the role of entropy and reversibility in a cosmological model.

Without understanding how a model treats equilibrium, entropy conservation, and the reversibility of expansion, any discussion of dark energy risks becoming speculative. That’s why I think these thermodynamic questions are the real starting point.

Claudio Marchesan

Hi Lorraine,

The point I’ve tried to question concerns a deep thermodynamic link — valid in both classical and relativistic contexts — between entropy conservation and reversibility. In the standard FLRW model this bi‑implication breaks down. The model assumes, through its structural hypotheses and mathematical formulation, that the CMB can undergo an isoentropic evolution that is treated as if it were reversible.

My open question is simply this: can such a process be considered physically meaningful?
What do you think?

Lorraine Ford

Claudio Marchesan
Claudio,

The equations might seem to indicate that the world is reversible, in theory. However, because of “quantum” number jumping, which is a type of irreversible ratchet, the world is not reversible, in fact.

Lorraine Ford

Lorraine Ford
Lay out the real-world mathematical system in front of you, and look at it objectively:

“Quantum number jumping” is the ONLY ratchet in the system, the ONLY directional element, and it is happening everywhere in the system.

And the system’s (or small parts of the system’s) knowledge of number change, due to this widespread quantum number jumping, and the flow-on number jumping due to mathematical relationships, is seemingly the only possible basis for the “time” category.

The combination of knowledge and mathematical analysis is the basis for the time category.

Time is algorithmically/ logically/ consciously derived.

Claudio Marchesan

Lorraine,

Quantum irreversibility is indeed a real phenomenon, but even when quantum effects are present, any macroscopic thermodynamic description must reduce to the classical limit.
In that limit we do have well-defined reversible transformations: for example, the quasistatic adiabatic compression of an ideal gas, or the reversible expansion in classical hermodynamics.

Lorraine Ford

Claudio Marchesan
Claudio,

Despite what the equations might seem to say, and despite what things might superficially look like, there is no actual blow-by-blow reversal happening. "Quantum number jumps" are a one-way ratchet on the system.

Lorraine Ford

Lorraine Ford
Physics is all about facing up to reality.

And the reality is that "quantum number jumps" mean that time can never be reversed.

It is as simple as that.

It is as simple as looking very closely at the actual world, as opposed to looking very closely at the equations which are merely an attempt to symbolically represent the world.

marcovici alexandru

@Forum Moderator at minute 29:40
when counting orders, and quasi orders, and posets and preorders and partial orders and asociative relations n' groups one could obtain obtain various numbers, that don't tell any story. the same way a person retain /remember the logo of a firm like [ first name logo visual identity of a brand that comes to mind]

why not an (~~extraterestrial~~ ) society where those structure are being learned like poetry in the first grade and are being juggled conversationaly casualy for the conversation sake and maybe structuraly by mathematicians

infusing / influencing the behavior a little bit in the visual realm because you cannot (?) sing a map

when counting one is uniqe. lets say two also is unique, three has some symmetry four is a tetrahedron there are some choices witch four are you talking about, five even more choices, from now own 6,7,8,9,10, 11 .. etc there is uncertainty when you say fifty seven(57), i don't know what number you are talking about .

604800 six hundred and four thousend and eighth hundred , is the naming with words, the receipt to arrive for certain at something ,can be chunked, factored
3*5^2*3*2^7*3*7 still from the above perspective is an extraterestrial beyond human comprehension number

this is whats needs to be trained human language worked with acting