Scientific consensus is not gospel dogma to be enforced, instead it should, and MUST change in the face of contrary data. There are theories like evolution, general relativity, and climate change which are truly settled science. Inflation (and string theory) are not there yet. Letters signed by 33 or 33,333 prestigious physicist won't make that so. Only data can.
On controversy over the article in Scientific American of ljjas, Steinhardt, and Loeb which has been objected to by 30 or so top experts including Steven Hawking we all need to remember the basic fundamental fact that appeal to authority is a logical fallacy. 30 experts disagreeing with one expert does not mean the 1 is wrong and the 30 are right. In science having 31or 3331 people agree with you, might get you a job and prizes, but it does not make you right. This is a basic fact of how science works.
Be skeptical of all theories while being open minded towards all theories until they fail to predict the outcome of experiments no matter who proposes them or where they are published. If they don’t make correct predictions the theory is wrong. Ijjas, Steinhardt, and Loeb relied on this basic fact of how science works for their article. The fact that lots of people believe otherwise without actual data to back them up does not make Ijjas, Steinhardt, and Loeb wrong.
Theoretical physics is in a state where our most widely accepted models resort to explanations with no more substance than the luminiferous aether. (A medium for light waves to travel in which Einstein’s Special Relativity showed was not needed). The difference is that in 2017 we find no evidence for our versions of the aether and then refuse to accept that we were collectively wrong. Ideas that are different like the cyclic model or f(R) gravity, or Loop Quantum Gravity, or work on the foundations of quantum mechanics are treated with a level of ... disdain if not censorship which is really disturbing. Especially when the most favored models, inflation, dark matter, and string/M-theory have so far failed to have their predictions prove up.
The simplest models of inflation predict strong gravitational waves that should have been seen with current instruments such as ESA's Planck satellite and various microwave telescopes (like BICEP). The very concept of the whole universe expanding exponentially requires some primordial gravitational wave background. Such a violent event would leave a signature and unless we find that then inflation is wrong. What can it be replaced with? Some would challenge me with that question. It is not the job of the skeptical, and we all have to be skeptical about everyone especially ourselves, to come up with a better model.
As Richard Feynman put it a model is wrong if it does not compare well to experiment. It does not matter who they are, what their name is, how beautiful the mathematics is, or how many people sign on to the theory. If that theory does not match observations it is wrong.
That is just basic science. Perhaps being a "mere" community college Adjunct Professor teaching Science 101 with a lab section to people who only need it to graduate has kept that basic fact in sharp focus. The scientific method is a process of from theory to testable hypotheses, which if proven out under experiment, establish the theory. Mathematical elegance and conceptual simplicity are not required by science and in and of themselves do not make a theory correct.
This applies to both Steinhart’s cyclic model and the standard big bang inflation LCDM model. As I understand his work, and I could be very wrong, it depends on M theory and the “brane world” model. While the LHC ruling out the best versions of the minimally super symmetric standard model pours cold water on the String/M-Theory party…it could be argued that some version of the brane-world model could still work out.
Certainly be skeptical about any theory I posit on this blog and publish. Be skeptical about any theory by anyone else too even if they are Hawking, or Witten, or Suskind, or t’Hooft. The name does not matter the math being pretty does not matter. If the data contradicts the theory the theory is wrong. That’s how it works. Right now, the lumineferous aethers of our time (Inflation,Dark Matter, SUSY Particles) may need to be found or the theories that depend on them need to be euthanized.
TL:DR; 1 Appeals to empirical data, or more precisely, the lack of data showing what the inflationary models predicted. 2 appeals to the niceness of the inflationary model for solving the cosmological problems it was proposed to solve. 2 also by having many authors with tons of prestige sign onto it appeals to authority, which is a logical fallacy. In science, in the court of data, the observations of an emeritus named chair professor are worth as much as those of a graduate student. In any argument the one with the data wins...or it's not science anymore.
PS which model do I like?
Well I did spend years researching a Lagrangian for the standard lambda CDM mode which tries to incorporate dark matter, and dark energy as a sector of particles similar to those we are made of but with which we do not directly interact. So I'd kinda like to see some evidence for inflation. Inspite of years of work on that, on the side, while I did my thesis on something more ... steady (massive star formation)... I let it go. The data does not support inflation having occurred like we once though it did.