# General Relativity

Posts on Einstein's general theory of relativity, both from the physical and mathematical points of views.

### Matter field from diffeomorphism: on a theme of Capoferri and Vassiliev

I try to reformulate an idea of Capoferri and Vassiliev in the infinitesimal limit and see where it goes.

### Newton-Cartan Gravity

A quick introduction of Newton-Cartan theory, which is a sort of Newtonian limit of general relativity from a geometric point of view.

### Traceless general relativity

A quick summary of the traceless version of general relativity.

### A Characterization of Geodesics

About the Einstein-Infeld-Hoffmann theorem characterizing geodesics.

### Conformal compactification of type (p,q) pseudo-Euclidean spaces

We explain how to conformally compactify pseudo-Euclidean spaces with $(p,q)$ signature.

### Purely kinetic initial data for Schwarzschild

Can initial data for Einstein's equation be specified in such a way that all the 'energy' are kinetic and not potential?

### Non-existence of multiple-black-hole solutions that look locally like subextremal Kerr-Newman

Paper announcement.

### The non-existence of black holes in (2+1) dimensional general relativity

We show that trapped surfaces cannot exist in (2+1) dimensional relativity.

### One and two (space-time) dimensional general relativity

Life is boring in low dimensions.

### Gravitational red shift and Killing horizons

The relationship between gravitational red shift and the surface gravity of black holes is explained.