Fred Combley Colloquia

Fred CombleyThe Fred Combley Lectures are a series of annual lectures given by distinguished researchers in the fields of physics and astrophysics. These lectures are of general interest to the major areas of research in the department.

The series is named after Fred Combley, a former Head of Department (1990-1995) and Dean of the Faculty of Science (1995-1998). Fred was an experimental particle physicist who worked with leptons and photons, contributing in the mid 70s to the first high-precision measurement of the anomalous magnetic moment of the muon. His work confirmed that positive and negative muons had the same anomalous magnetic moment, set a much improved upper limit on the muon electric dipole moment and tested the time dilation formula of special relativity.

Despite the heavy administrative load he shouldered as Head of Department and then Dean of Faculty, he continued to be a conscientious and supportive supervisor of research students and an effective group leader. Fred was an inspirational and innovative teacher. He pioneered the use of personal computers in university teaching and learning, and later was the first member of the department to develop an entirely student-led lecture course. He was immensely popular with the students and much in demand as a project supervisor.

An excellent speaker himself, Fred was passionate about communication and an enthusiastic supporter of departmental seminars and colloquia. The bell donated to the Department in his memory recalls his habit of rousting colleagues and students out of their offices to come and listen to a seminar, even if its subject matter was not immediately relevant to their research interests.

The information for the invited talks is below, with the respective contact person in each case.


Schedule for 2019 Colloquia

Area of research Name Date, time and location
Particle Physics and Particle Astrophysics

Professor Joseph Giaime, Louisiana State University

Wonderful collisions: gravitational wave observation and astrophysics

Abstract:
A century ago,, Einstein's theory of general relativity was first published, describing the relationship between gravity and spacetime curvature.  This was soon followed by a wave solution to the Einstein equation.  Around half a century later, work began to observe those waves, expected to be emitted by energetic astrophysical sources.  There followed decades of work by generations of scientists and engineers around the world, including the development and operation of multi-ton bar antennas and long-baseline interferometric detectors.  In fall 2015, gravitational waves from a binary black hole merger were observed using the Laser Interferometer Gravitational-wave Observatory (LIGO).  After two complete observational runs and joint analysis of the European Virgo observatory data with that of LIGO's two U.S. sites, we released a catalogue of 10 black-hole binary mergers and 1 neutron star binary merger. 

We are preparing for a third, year-long, observational run in Spring 2019, with a goal of increased detection range and better signal-to-nlise ratios.  I will describe these wonderful collisions, both the compact object mergers and those between gravitational-wave science with the rest of multi-messenger astronomy, beginning with the widely-observed neutron star event in August 2017.

Contact: Dr Ed Daw (e.daw@sheffield.ac.uk)

13:30, Wednesday 6th March 2019
LT 1, Diamond

Inorganic Semiconductors

Professor Jonathan Knight, University of Bath

Better optical fibres     

Abstract:

Optical fibres have been a major technological success.  However, they have profound performance limitations that are intrinsic to their basic physics.  These arise as a consequence of the fact that in all conventional optical fibres, light travels through a solid glass, and the performance limits of the glass become the best one can obtain from the optical fibre.  Properties limited in this way include the fibre's spectral transparency, power-carrying capacity, optical nonlinear response, dispersion and optical damage characteristics.  For several decades researchers have worked to overcome these constraints by developing an alternative optical fibre technology - one not based on total internal reflection, and where light can be trapped in an air core.  Progress over more recent years has been transformative, both in terms of refining our understanding of how the required performance enhancements can be achieved and in demonstrating that conventional optical fibres really can be outperformed - often by many orders of magnitude. 

This talk will briefly describe the history of this field of research and then focus on the science and the extraordinary technical achievements of the last few years.

Contact: Professor Maurice Skolnick (m.skolnick@sheffield.ac.uk)

14:00, Wednesday 15th May 2019
LT 7, Hicks Building

Astronomy and Astrophysics

Professor Carlos Frenk, Durham University

A conclusive test of the existence of cold dark matter

Abstract:

The "Lambda cold dark matter" (LCDM) cosmological model is one of the great achievements in Physics of the past thirty years.  Theoretical predictions formulated in the 1980s turned out to agree remarkably well with measurements, performed decades later, of the galaxy distribution and the temperature structure of the cosmic microwave background radiation.  Yet, these successes do not inform us directly about the nature of the dark matter.  Indeed, there are competing (and extremely controversial) claims that the dark matter might have already been discovered, either through the annihilation of cold, or the decay of warm, dark matter particles.  In astrophysics the identify of the dark matter manifests itself clearly on subgalactic scales, including the dwarf satellite galaxies of the Milky Way and even less massive dark matter objects, too small to have made a galaxy.

Professor Frenk will discussion predictions from cosmological simulations assuming cold and warm (in the form of sterile neutrinos) dark matter and show how forthcoming astronomical observations can conclusively distinguish between the two.

Contact: Professor Paul Crowther 
(physics-hod@sheffield.ac.uk) 

13:30,Wednesday 6 November 2019
Venue to be confirmed