Whitney Extension and Counterexample to Sard's Theorem
In a first course in differential geometry/topology we are often taught the following version of Sard's theorem: Theorem …
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.
Mariş's Theorem
We describe a theorem due to Mihai Mariş concerning the symmetries of ground states.
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.
Repeating Decimals
When does the decimal expansion of a number end with one digit repeated?
A Cute Little Wave Estimate
Let us consider first the linear wave equation \[ \Box u = 0\] on (1+d)-dimensional Minkowski space. A well known property of the wave …
Where Does The π Go
It is fairly well known that experts in partial differential equations and experts in harmonic analysis prefer to define the Fourier …
How to ballast your ship or why my kitchen sink is always dirty
Recently I've been reading a bit of fluid dynamics, and came across the classical problem of free and forced vortices. In this post I …
