Monthly Archives: July 2015

Spectral analysis in resonant interferometry: following the traces of thermal deformation

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How researchers from the LIGO scientific collaboration use signals generated from higher-order mode resonances to glean crucial information about the thermal state of their interferometers.

Chris Mueller

Chris Mueller received his Ph.D. in physics with Guido Mueller at the University of Florida and has since moved to industry.

Imagine for a moment that you’ve accepted the challenge of trying to make the first direct detection of gravitational waves. To achieve such a daunting task you’ll need to devise an instrument capable of measuring a change in length of just 10-19 m over a distance of several km. At these length scales everything matters; the ground is vibrating, air molecules are buzzing around, and the molecules which make up the test masses of your detector are quivering. This challenge is precisely Continue reading →

How wild can a static spacetime get?

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Stationary spacetimes—sounds fairly simple, unchanging.  Static—even more boring.  But are they?

Steve (Stacey) Harris

Steve (also known as Stacey) Harris is a mathematical relativist in the Department of Mathematics at Saint Louis University, mostly working on global structures such as causal boundary, and a notorious campus gadfly and rebel, being active in AAUP and fanatical about shared governance. Off campus there’s hiking and playing flute in concert band.

Consider an experiment of emitting a photon along a closed path—closed either due to a constraining light-tube or due to a topological closure in the spacetime—and finding the time till the photon returns to the starting point.  (Our naive expectation is for the time to be the same as the length of the path, if our clocks and measuring rods are in geometric units, set to show speed of light is unity.)  Now turn around and emit a photon along the same path but in the reverse direction—does it take the same time to Continue reading →

Can’t solve an equation….bypass it !!!

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Radouane Gannouji

Radouane Gannouji is an associate professor at the Department of Physics, PUCV.

In general relativity, to understand how the spacetimes behave in presence of a given form of matter, we have to solve the Einstein field equations, which in general, are a set of 10 very complicated coupled nonlinear second order partial differential equations that describes the fundamental interaction of gravitation as a result of spacetime being curved by matter and energy. Once we solve these set of field equations we get the metric of the spacetime that describes all the general important physical features of the spacetime, for example Continue reading →

The return of Newton-Cartan geometry

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Jelle Hartong

Jelle Hartong is a postdoctoral researcher at the Université Libre de Bruxelles. His research concerns the foundations and applications of various non-AdS holographies and non-relativistic gravity.

Non-relativistic field theories defined on Newton-Cartan Geometry and its extension called Torsional Newton-Cartan Geometry, have (re-)appeared in recent studies of non-AdS holography and condensed matter physics.

Relativistic, Poincaré invariant, field theories are defined on Minkowski space-time. This flat background can be turned into a curved geometry by coupling the theory to a Lorentzian metric as one does when adding matter to Einstein’s theory of gravity. There are many areas of physics, notably Continue reading →