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Anti-inflation quacks supported not by science but by special anti-science social interests

Sabine Hossenfelder wrote a rant:

I totally mean it: Inflation never solved the flatness problem.
I would personally never allow a student to get a degree from theoretical physics or something like that if she were a quack like her who just doesn't get the most fundamental ideas in the field – and she doesn't. But there are good reasons why she can "totally mean it". Quacks like her may do well because while her total scientific incompetence is a minus from the viewpoint of the actual experts, it's a plus from the viewpoint of the bad people "around" science.

For example, George Soros just gave $18 billion (80% of his wealth) to his "charities". You can be sure that a part of this money will be used to attack science, just like it was used in recent years. Obnoxious antiscientific whores aren't that bad, are they? In fact, they are good, discriminated against by the evil white male scientists, so why don't we turn statements like "inflation never solved the flatness problem" in a virtue that should be rewarded?

Just try to appreciate how much evil may be done with $18 billion that is sent to carefully, ideologically picked corners.

The whole system underlying science and other meritocratic human activities – at least those whose importance isn't "immediately" impacting the well-being of the ordinary Joe – is collapsing as the people allow scum like George Soros to create "compensating" anti-meritocratic structures that switch the evolution into the reverse: What sucks gets to the top.




Cosmic inflation is also about the "reversal of the dynamics" and that's why it's unquestionable for an expert – or an intelligent student in fields related to cosmology – that it must be considered a vital part of our current understanding of the history of the Universe.




I have explained why inflation solves – and is basically needed to solve – the flatness problem e.g. in my article celebrating Alan Guth or an answer at Physics Stack Exchange. Hossenfelder mixes inflation and initial conditions in weird and illogical ways.

But the cosmic inflation really is needed and it is needed to prepare viable initial conditions for the subsequent evolution according to the equations of the big bang theory. How does it work?

General relativity allows you to derive that in a uniform, isotropic Universe, the flat \(\RR^3\) slices may survive in time, during the expansion, if the matter density is "critical". So the matter density divided by some function of Hubble's constant etc. is called \(\Omega\) and \(\Omega=1\) means that the Universe is flat at a given moment and stays flat despite the expansion.

But it's never exactly flat and we may study how \(\Omega-1\) evolves with time. Pretty much by the definition of \(\Omega\) I mentioned, we may know that\[

\Omega-1=\frac{k}{a^2H^2}-\frac{\Lambda}{3H^2}

\] And by Einstein's equations, we may study how \(|\Omega-1|\) increases or decreases with time. We find out that today, in the "normal" big bang expansion, it increases with time. The Universe is getting less flat as it gets older. Because it's still rather flat today, \(|\Omega-1|\leq 0.01\) or so, we may see that it was extremely flat seconds after the big bang, perhaps with\[

|\Omega-1| \approx 10^{-{\rm dozens}}

\] If you dig deeper and study increasingly early moments of our Universe, you will see – just because of Einstein's equations – that the Universe was increasingly unnaturally flat, and it was almost precisely flat at each corner. It means that our big bang theory only works is you supplement it with initial conditions that must be special – they must respect the extremely precise flatness at each point of the Universe.

Now, you should pick your initial conditions and/or logic to estimate whether one choice of them is likely or not. But because the value of \(|\Omega-1|\) has to be this unnaturally tiny, and it must hold independently at each of the zillions of places of the Universe, the normally calculated probability according to any sensible framework will be something like\[

10^{-{\rm dozens} \times N}

\] where \(N\) is the number of "independent" regions of the Universe that you need – you needed to impose the unlikely flatness for each of them. The probability is therefore insanely low. When some probability is this low, you could use it to disprove the theory – disprove the big bang theory. That's how we disprove theory. A scientific hypothesis is disproved if you can show that it depends on events that are predicted to be immensely unlikely. An immensely unlikely assumption that is needed may be translated to a very low probability that the hypothesis itself is right. That's how Bayesian reasoning and science work.

So you should better have some extra piece of the theory that says that these very flat initial conditions aren't really that insanely unlikely. And inflation is that extra piece – and, up to plagiarism and small modifications, and up to proposals whose success in achieving flatness hasn't been understood by many people (string gas cosmology), it's still generally considered to be the only known piece that can play this role.

How does inflation solve the flatness problem? It simply adds the terms to the expansion coming from the "temporary cosmological constant" \(V(\phi)\), the inflaton potential, and from the kinetic term of the inflaton, \((\dot\phi)^2\). And when the inflaton sits or moves far enough from the minimum of \(V(\phi)\), you will be able to see that there are new terms that decide about the time evolution of \(|\Omega-1|\). You remember I wrote that \(|\Omega-1|\) is increasing with time today? OK, so inflation simply adds new terms that reverse the overall evolution. As the Universe is getting older, \(|\Omega-1|\) is getting smaller during inflation – the Universe is getting flatter. It's doing so everywhere where the corresponding condition for the inflaton, basically \(V(\phi)\gt (\dot\phi)^2 \), is obeyed.

So from Einstein's equations applied to the well tested ordinary big bang expansion, we know that a second after the beginning, the Universe was extremely flat – even flatter than today, by the smallness of \(|\Omega-1|\). Why was it so flat? Because there was a previous era that made it flat. It made it almost precisely flat by a mechanism that is pretty much as simple and straightforward as the mechanism that makes it less flat today. There is just a new term with the opposite sign.

To some extent, some inflation or its "generalization" had to be there because we almost directly observe it. It's like a hot soup. The soup is too hot so you're waiting when it gets colder so that you don't burn your mouth when you eat it. While you're waiting, you may ask why it was so hot to start with? Well, you correctly guess, it's probably because someone heated it up. Some cook or heater or somebody like that. It's exactly the same with the flatness. We see that the flatness goes down – becomes less perfect (like cooling soup). Why was it so immensely flat (hot soup) in the past? Because there was a previous process that just made it flat.

What's so impenetrable about these basic ideas that people pretending to deserve their physics PhDs brag that "they really mean it" that this explanation doesn't work in some weird way? How it could not work? Her text and her title is exactly as indefensible as a comment of a visitor of the restaurant:
I totally mean it: heaters and ovens have never really solved the problem why the food got hot before the waitress brought us the food!
Oh, really? So what's the explanation that the soup was hot? Why would a sane and honest person deny even the very modest fact that we have quite some evidence that some mechanism has heated the soup before the waiter brought it to us?

You know, almost everyone who has at least "some" credentials in cosmology knows that Guth, Linde, and pals – and interpreters of those discoveries such as your humble correspondent – are right while Hossenfelder is just totally wrong. The evidence is totally on our side and the likes of Hossenfelder are demonstrably wrong. But in our intellectually deteriorating society, this fact is becoming increasingly irrelevant. The likes of Hossenfelder have been building a whole network of alternative institutions of fake science, one that has almost completely merged with the Soros-style network and the PC media.

I think that the letter of the top inflation researchers symbolized this immense gap. Pretty much everyone who has done something important in that field or related fields understands the case for inflation, the depth of the inflationary ideas, and their unmatched ability to explain the strange and seemingly unlikely features of the initial conditions that the normal big bang expansion requires. But you could see that all these top physicists and Nobel prize winners etc. didn't seem to make almost any impact on the broader "community" of the writers about science and stuff like that. An abyss has been growing for decades – and the top scientists' decision to avoid nontrivial interactions with the media has helped the growth. It's time to realize that this abyss is real and has become dangerous for the very survival of science.

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