I only began to understand Galois Theory when I picked up Janelidzes book.
In the first chapter he covers the usual Galois Theory and mentions of course that an adjunction between posets is a Galois Connection. This is categorified up a categorical level as described here in nlab. They mention:
It is the particular case where the 2-relation $R$ is the hom-functor $S^{op}×S\rightarrow Set$; the corresponding adjunction is something which Lawvere calls conjugation.
In the second chapter, Janelidze covers the Galois Theory of Grothendieck, but not in:
in its full generality, that is in the context of Schemes: this would require a long technical introduction. But the spirit of Grothendiecks approach is applied to the context of fields.
These notes by Lenstra do. He also mentions Galois Categories (as Janelidze does not)and this links up with the Tannaka-Krein Reconstruction.
In the fourth chapter, besides mentioning the Pierce Spectrum, which is an interesting variation on the Zariski Spectrum and links up to Stone Spaces, he mentions effective monadic descent
In its more specific meaning descent is the study of generalizations of the sheaf condition on presheaves to presheaves with values in higher categories.
The descent is monadic when the pseudo-functor, aka the 2-presheaf, in its fibered category avatar (by the Grothendieck construction) are bifibrations. This allows the use of monads. He also mentions internal presheafs which are a concept in Enriched Category Theory.
In Chapter five, Janelidze relativises these concepts in the context of slice categories in preparation of proving the Abstract Categorical Galois Theorem.
This is extended in Chapter seven to 'Non-Galoisian Galois Theorem' by removing the Galois condition on effective descent, and by way of the Joyal-Tierney Theorem places it in the context of Grothendieck Toposes.
NLab goes on to say:
For $K$ a field let $Et(K)$ be its small étale site. And let $\bar{E}:=Sh(Et(K))$ be the sheaf topos over it. This topos is a
- local topos
- locally connected topos
- connected topos
Then Galois extensions of $K$ correspond precisely to the locally constant objects in $\bar{E}$. The full subcategory on them is the Galois topos $Gal(\bar{E})\rightarrow \bar{E}$.
The Galois group is the fundamental group of the topos.
Hence, they conclude:
Accordingly in topos theory Galois theory is generally about the classification of locally constant sheaves. The Galois group corresponds to the fundamental group of the topos.
This can then be established in higher Topos Theory where a cohesive structure on the higher topos is used to make the constructions go through.
Proposition. For $H$, a ∞-topos that is:
- locally ∞-connected
- ∞-connected,
We have a natural equivalence $LConst(X)\backsimeq ∞Grpd[Π(X),∞Grpd_{\kappa}]$
of locally constant ∞-stacks on $X$ with ∞-permutation representations of the fundamental ∞-groupoid of $X$.
One, ought to here make the connection with the usual classification of topological covering spaces:
Let $X$ be a topological space, that is:
locally connected
connected
then, $Cov(X)\backsimeq Top[\pi (X),Set]$
I'm not sure I would say I'm an expert in information geometry. However, I worked for several years on the subject as a postdoc. As a disclaimer, this is entirely my own opinion and others may disagree.
Since you asked this question, the research situation in the field has improved. Firstly, two separate books ([1$ $], [2$ $]) have been published, both of which are good references for the material. In particular, the second gives a rigorous mathematical treatment for the basic theory. Secondly, a new journal, Information Geometry, has been released. Thus far several issues have been published and they contain some interesting papers.
However, information geometry is definitely a relatively niche mathematical field. As to the reason for this, in my opinion IG is really an interdisciplinary field and not simply a branch of mathematics. Many of the people working in the field are not mathematicians by background. As a result, information geometry embodies a wide range of research. Some papers are mathematical, but many others are really statistics, computer science, or some hybrid thereof. Many of the publishing conventions are differ from math, as well. For instance, it's common to publish short papers without proofs in conference proceedings and, generally speaking, the main theorems are not stated in the introduction.
While there is a lot of good work being done in the field, there is also too much research that is not really serious. Most of this is not done in bad faith, but due to a lack of experience and background in geometry. Furthermore, a lot of the work is published in a for-profit journal whose peer review process is minimal. Without giving examples, some papers boil down to slightly modifying known results and treating them as novel. Other papers try to use really big ideas without understanding the underlying theory or really proving anything. Furthermore, what is considered acceptable overlap between publications is far greater than in pure math. Needless to say, these issues create serious problems for the field, and makes it much less likely to be taken seriously.
Even with the good papers, they often seem to lack a good punchline. As was mentioned in the comments, the math in IG has built up a very general foundational theory, often without providing mathematical or statistical motivation for this theory. My impression is that quite a few of the researchers in the field were heavily influenced by the "structural point of view" pioneered by Nomizu and Kobayashi. I suppose the motivation for these structures might be self-evident to a statistician, but as a geometer oftentimes it's completely lost on me. In my experience, I only really started to understand what was going on when I worked through some important examples of statistical manifolds, instead of trying to learn the theory from the ground up.
Related to the point above, it's difficult to find explicit conjectures in the field. There isn't something similar to Yau's list of open problems in geometry to guide progress in the field. As such, when I was learning the field it was hard to tell what was considered an important problem and to understand the motivations for the research.
As a result of all of these factors, information geometry has remained a specialized sub-field. I think this will remain the case unless it is used to solve a big problem or it evolves to be more in line with standard mathematical conventions. All that being said, I've learned a lot from information geometry, and there is definitely a fair amount of low-hanging fruit to be picked. Furthermore, the field seems to be making progress in recent years, so hopefully my critiques will soon be obsolete.
To end on a positive note, let me give an example of a paper that I think does things well [3$ $]. This work studies necessary conditions for a Riemannian manifold to locally be written as the Hessian of a convex potential. I really like this paper and have found it helpful for my intuition.
P.S. If anyone is interested, I was able to find a list of open problems from 1998, some of which have since been solved.
References
[1$ $] Amari, S. I. (2016). Information geometry and its applications (Vol. 194). Tokyo: Springer.
[2$ $] Ay, N., Jost, J., Vân Lê, H., & Schwachhöfer, L. (2017). Information geometry (Vol. 8). Berlin: Springer.
[3$ $] Amari, S. I., & Armstrong, J. (2014). Curvature of Hessian manifolds. Differential Geometry and its Applications, 33, 1-12.
Best Answer
Since you have done representation theory, you should have a look at Persi Diaconis wonderful:
http://projecteuclid.org/DPubS?service=UI&version=1.0&verb=Display&handle=euclid.lnms/1215467407
(which can be downloaded freely from that link). It should contain a lot of possible projects!, P Diaconis often uses the frase " somebody should look into this ... " There is a lot which is undone there!