5 papers
On the viability of minimal HoÅava gravity
Ted Jacobson, Pranav Pulakkat
HoÅava gravity is a Lorentz-violating modification of general relativity (GR) with a preferred spacelike foliation. Observational evidence has put strong constraints on the parame…
Guiding-centre Lagrangian and quasi-symmetry
Ted Jacobson
A charged particle in a suitably strong magnetic field spirals along the field lines while slowly drifting transversely. This note provides a brief derivation of an effective Lagra…
Feynman 1947 letter on path integral for the Dirac equation
Ted Jacobson
In 1947, four months before the famous Shelter Island conference, Richard Feynman wrote a lengthy letter to his former MIT classmate Theodore Welton, reporting on his efforts to de…
The enigmatic gravitational partition function
Batoul Banihashemi, Ted Jacobson
The saddle point approximation to formal quantum gravitational partition functions has yielded plausible computations of horizon entropy in various settings, but it stands on shaky…
On the lapse contour in the gravitational path integral
Batoul Banihashemi, Ted Jacobson
The gravitational path integral is usually implemented with a covariant action by analogy with other gauge field theories, but the gravitational case is different in important ways…