Quantum mechanics meets CMB physics

by Massimo Giovannini.


Since 1991 Massimo Giovannini has extensively researched, taught and written on high-energy physics, gravitation and cosmology. He wrote over 180 papers and various review articles. He is the author of a book entitled “A primer on the physics of Cosmic Microwave Background” published in 2008.

Which is the origin of the temperature and polarization anisotropies of the Cosmic Microwave Background? Classical or quantum? The temperature and the polarization anisotropies of the Cosmic Microwave Background (CMB) are customarily explained in terms of large-scale curvature inhomogeneities. Are curvature perturbations originally classical or are they inherently quantum mechanical, as speculated many years ago by Sakharov?

In the conventional view these questions are quickly dismissed since the quantum origin of large-scale curvature fluctuations is, according to some, an indisputable fact of nature. This is true if and when Continue reading

Want to crush a singularity? First make it strong and then …

by Parampreet Singh.

Parampreet Singh

Parampreet Singh with a young student who often asks him the most difficult and so far unanswerable questions on the resolution of singularities. Dr Parampreet Singh is Associate Professor at Department of Physics and Astronomy at Louisiana State University.

Einstein’s theory of classical general relativity breaks down when spacetime curvature
becomes extremely large near the singularities. To answer the fundamental questions
about the origin of our Universe or what happens at the central singularity of the black holes thus lies beyond the validity of Einstein’s theory. Our research deals with discovering the framework which guarantees resolution of singularities.

It has been long expected that quantum gravitational effects tame the classical singularities leading to insights on the above questions. A final theory of quantum gravity is not yet there but the underlying techniques can be used to understand whether quantum gravitational effects resolve cosmological and black hole singularities. Our goal is Continue reading

Tilting laser beams in LISA

by Michael Tröbs.

Michael Troebs in the lab

Michael Tröbs in the lab. Michael Tröbs is an experimental physicist at Max Planck Institute for Gravitational Physics (AEI). The LISA optical bench test bed was built in collaboration with Airbus DS and University of Glasgow. At AEI Michael is responsible for the project.

A testbed to experimentally investigate tilt-to-length coupling for LISA, a gravitational-wave detector in space.

The planned space-based gravitational-wave detector LISA will consist of three satellites in a triangle with million kilometer long laser arms. This constellation will orbit the Sun, following the Earth. LISA is expected to be laser shot-noise limited in its most sensitive frequency band (in the Millihertz range). The second largest contribution to the noise budget is the coupling from laser beam tilt to the interferometric length measurement, which we will call tilt-to-length (TTL) coupling in the following.

How does tilt-to-length coupling come about? Continue reading

Setting space on fire

by Yasaman K. Yazdi and Niayesh Afshordi.

Niayesh Afshordi and Yasaman Yazdi discover that firewalls have consequences

Niayesh Afshordi and Yasaman Yazdi discover that firewalls have consequences. Yasaman K. Yazdi is a PhD candidate at the University of Waterloo and the Perimeter Institute for Theoretical Physics. Niayesh Afshordi is an associate professor at the University of Waterloo and the Perimeter Institute for Theoretical Physics.

Thought experiments highlight the edge of our understanding of our theories.  Sometimes, however, we can get so caught up in heated debates about the solution to a thought experiment, that we may forget that we are talking about physical objects, and that an actual experiment or observation may give the answer.  In this Insight we discuss a proposed solution to the black hole information puzzle, and a possible observational signal that might confirm it.


The black hole information puzzle and a potential solution

The black hole information loss problem is a decades old problem that highlights the tensions between some of the pillars of modern theoretical physics. It has evolved from being Continue reading