Matt Visser: Recent Seminars
Some recent seminars I have presented.
(These are separated into general interest seminars and technical seminars.)

Lectures for the general public

Technical seminars for specialists

The NZ seminars supported by FQXi
These are all postscript and/or PDF files of the transparencies, often with colour.
Recent talks are PDF that has been exported from the Keynote software package running on a Mac.
Some of these seminars (especially the ones that are heavy on graphics) use multi megabyte files  be patient.
You will need ghostview, or something similar, to get anything useful out of this webpage.
If ghostview gives you some blurry patches  try turning OFF the antialiasing.
If kghostview does not seem to work  try xpdf.
If your PDF viewer can't handle superscripts/ subscripts/ some of the strange fonts I use
 then unfortunately there is no really simple fix
 it's time to upgrade your PDF viewer...
 Theory and Observation in black hole physics [PDF]

Theory and Observation in black hole physics [postscript]
 Schwarzschild and Kerr black holes [PDF]
 Wurmlochur und Zeitreisen/ Wormholes and time travel. [postscript]

Wurmlochur und Zeitreisen/ Wormholes and time travel. [PDF]
Wellington Library
International Year of Astronomy Lecture Series, September 2009.
This is a lecture to the general public; part of the international year of astronomy lecture series.
VUW Science Faculty Lecture Series, 2009.
New Plymouth, New Zealand, July 2009.This is a lecture to the general public.
Te Papa (National Museum of New Zealand)
International Year of Astronomy Lecture Series, May 2009.
This is a lecture to the general public; part of the international year of astronomy lecture series.
Wellington Astronomical Society
International Year of Astronomy Lecture Series, May 2009.
This is a lecture to an amateur astronomy society; part of the international year of astronomy lecture series.
VUW Science Faculty Lecture Series, 2008.
New Plymouth, New Zealand, October 2008.This is a lecture to the general public.
Phoenix Society Astrocamp 2008.
This is a lecture to an amateur astronomy society.Hudson Lecture 2007.
Hudson memorial lecture of the Royal Society of New Zealand, Wellington Branch, May 2007.Semitechnical lecture on cosmology suitable for the general public.
Inaugural Lecture 2007.
Inaugural professorial lecture at Victoria University of Wellington, New Zealand, 20 March 2007.Semitechnical lecture on my research suitable for the general public.
Abstract: Is "quantum gravity" even the right question to be asking? It is increasingly plausible that Einstein's general relativity (like Euler's hydrodynamics), is "merely" a lowenergy approximation to some radically different "fundamental" theory. Professor Visser will present a nontechnical description of what might be going on, and what the prospects are for future progress.
Carter Observatory: Teachers' day 2006.
National Observatory of New Zealand, April 2006.Semitechnical lecture on black holes for highschool astronomy teachers.
Wellington Astronomical Society 2005.
RSNZ, Science House, April 2005.Semitechnical lecture for amateur astronomers.
Sixatsix (Victoria University Extension programme) 2005.
Rutherford House, Wellington, March 2005.Lecture for the general public.
Phoenix society 2004.
RSNZ, Science House, October 2004.Lecture aimed at an audience consisting mainly of amateur astronomers.
Royal Society NZ [Physics] 2003.
Wellington, August 2003.Somewhat more technical talk on black holes, similar to the Phoenix society lecture.
Phoenix Society 2003.
Wellington, Wairarapa, March 2003.This is a nontechnical talk on black holes.
Raum, Zeit, und Jenseits 2003.
Neuen Galerie Luzern, January 2003.This is a short nontechnical talk on traversable wormholes, time travel, and Stephen Hawking's "Chronology Protection" conjecture.
7 x 7 series on science, technology, and society 2002.
Wellington, New Zealand, November 2002.This is a very short [7 minute] nontechnical talk on "analogue models" for curved spacetime and "artificial black holes".
 Analogue spacetimes: toy models for "quantum gravity" [PDF]
 Cosmographic tests of the Hubble law: How far can we really go without a specific model for the cosmological equation of state? [PDF]
 Bounding the Bogoliubov coefficients [PDF]
 Vorticity in the acoustic analogue of gravity. Part 1 [PDF]
 Vorticity in the acoustic analogue of gravity. Part 2 [PDF]

Vorticity in the acoustic analogue of gravity. Part 3 [PDF]
 Quantum Physics of Chronology Protection. [postscript]
 Quantum Physics of Chronology Protection. [PDF]
 Wormholes and nontrivial topology. [postscript]

Wormholes and nontrivial topology. [PDF]
 Quantum Physics of Chronology Protection. [postscript]

Quantum Physics of Chronology Protection. [PDF]
 From Lagrangians to pseudoRiemannian geometry: Modelling Einstein's gravity. [postscript]

From Lagrangians to pseudoRiemannian geometry: Modelling Einstein's gravity. [PDF]
 Acoustics in BECs as an example of broken Lorentz symmetry. [postscript]

Acoustics in BECs as an example of broken Lorentz symmetry. [PDF]
 Essential and inessential features of Hawking radiation. [postscript]

Essential and inessential features of Hawking radiation. [PDF]
 Effective geometry in the Casimir vacuum. [postscript]

Effective geometry in the Casimir vacuum. [PDF]
 Analog models of General Relativity: Introduction and Survey. [postscript]

Analog models of General Relativity: Introduction and Survey. [PDF]
 Living on the edge: Cosmology on the boundary of antide Sitter space [postscript]

Living on the edge: Cosmology on the boundary of antide Sitter space [PDF]
 Wormholes and warpdrives: peculiarities in general relativity [postscript]

Wormholes and warpdrives: peculiarities in general relativity [PDF]
 Energy conditions and their implications [postscript]

Energy conditions and their implications [PDF]
 Wormholes, warp drives, and other weirdness [postscript]

Wormholes, warp drives, and other weirdness [PDF]
Emergent gravity IV.
University of British Columbia, Vancouver, Canada, August 2009.
Conference website.This is a technical seminar I presented at the 4th conference on Emergent Gravity:
This seminar is based on joint research with Silke Weinfurtner (UBC) and Thomas Sotiriou (Cambridge, UK).
University of British Columboa, Vancouver, September 2009.
This is a technical seminar I presented at the Physics and Astronomy Department at UBC Vancouver:
This seminar is based on joint research with Celine Cattoen.
DARK2009.
Christchurch, New Zealand, January 2009.
Conference website.This is a technical seminar I presented at the Seventh International Heidelberg Conference on Dark Matter in Astro and Particle Physics:
This seminar is based on joint research with Celine Cattoen.
Black Holes in General Relativity and String Theory.
Veli Losinj, Croatia, August 2008.
Conference website.These are two technical seminars I gave at the workshop on Black Holes in General Relativity and String Theory held at Veli Losinj, Croatia, in August 2008.
UBC, Vancouver, British Columbia, 2008.
These are two technical seminars I gave at the University of British Columbia, Vancouver, Canada, in July 2008.Centro de Estudios Cientificos, Valdivia, el Chile, 2008.
This is a series of three technical seminars I gave at the "Centro de Estudios Cientificos" in Valdivia, Chile, during a brief stay in April 2008.NZMS/AMS Joint International Conference, 2007.
Joint meeting of the New Zealand Mathematical Society and the American Mathematical Society.Victoria University of Wellington, New Zealand, December 2007.
Conference website.
Technical presentation on emergent spacetimes.
This plenary talk is more aimed at mathematicians, and tries to indicate why these mathematical structures are interesting.
Abstract: The theoretical physics community is increasingly pushing at the boundaries of classical differential geometry (Riemannian and Lorentzian manifolds), and seeking new mathematical tools to investigate various extensions of Einstein gravity. Among the as yet mathematically imprecise concepts being mooted are the notions of emergent spacetime (where the manifold picture breaks down at short distances), rainbow geometries (where the ``metric'' somehow depends on energy and momentum), and particular unexplored subclasses of pseudoFinsler geometry. I will outline why these ideas are considered interesting, and indicate some of the foundational mathematical issues that remain open.
Effective models for quantum gravity, 2007.
Perimeter Institute, Waterloo, Canada, November 2007.Conference website.
Technical presentation on emergent spacetimes.
Experimental search for quantum gravity, 2007.
Perimeter Institute, Waterloo, Canada, November 2007.Conference website.
Technical presentation on emergent spacetimes.
The dispersion relations that naturally arise in the known emergent/analogue spacetimes typically violate analogue Lorentz invariance at high energy, but do not do so in completely arbitrary manner. This suggests that a search for arbitrary violations of Lorentz invariance is possibly overkill: There are a number of natural and physically wellmotivated restrictions one can put on emergent/analogue dispersion relations, considerably reducing the plausible parameter space.
ENRAGEing Ideas, 2007.
Utrecht University, The Netherlands, September 2007.Conference website.
Technical presentation on emergent spacetimes.
Time and Matter 2, 2007.
Lake Bled, Slovenia, August 2007.Conference website.
Technical presentation on emergent spacetimes.
Seminar at LMU, Munich, Germany, 2007.
August 2007.Technical presentation on emergent spacetimes.
GR18 Conference, 2007.
Sydney, Australia, July 2007.Conference website.
Two technical presentations:
The cosmographic seminar is based on joint research with Celine Cattoen.
NZIP Conference, 2007.
New Zealand Institute of PhysicsOtago University, New Zealand, July 2007.
Conference website.
Two technical presentations:
The cosmographic seminar is based on joint research with Celine Cattoen.
From Quantum to Emergent Gravity: Theory and Phenomenology, 2007.
SISSA, Trieste, June 2007.Conference website.
Technical presentation on emergent spacetimes.
Abstract: We develop several models for "rainbow geometries" based on "analogue spacetimes". These geometries are useful as concrete physical examples of how to construct physically wellmotivated rainbow geometries, which may then be of interest as guideposts when considering possible energydependent modifications of general relativity. One class of models is based on generalizing the acoustic spacetimes of classical fluid mechanics by inserting the momentumdependent group velocity and phase velocity into the spacetime metric  this leads to two distinct "rainbow metrics", which describe distinct aspects of the physics, and which converge on the ordinary acoustic metric in the hydrodynamic limit. A second class of energydependent geometries can be built by using the Maupertuis form of the least action principle to rewrite Newton's second law in terms of geodesic equations on an energydependent manifold. While these particular models are not themselves of direct relevance to quantum gravity, they do provide mathematically and physically welldefined examples of what a "rainbow spacetime" should be.
COSLAB conference, 2006.
Leiden University, The Netherlands, September 2006.Technical presentation on emergent spacetimes.
VictoriaCanterbury Meeting, 2005.
Victoria University, January 2005.Lecture for an informal Victoria University/Canterbury University microconference on General Relativity.
SISSA, Trieste, 2004.
December 2004.Lecture similar to that at the Hawking 60 conference in 2002, (see below), but this particular talk was aimed at an audience consisting mainly of classical astrophysicists.
WellingtonManawatu Applied Mathematics Meeting
Massey University, October 2004.Lecture presented at the 2004 Victoria University/Massey University microconference on applied mathematics. (Similar to GR17 talk; modified for a different audience.)
KerrFest, 2004.
Canterbury University, August 2004.GR 17 Conference, 2004.
Dublin, July 2004.These are two short talks (20 minutes each), one on simulating Kerr black holes with a vortex flow, and another on "jerk" and "snap" in cosmology.
Vortex 2004
Cargese, Corsica, France, July 2004.This is a short course (2.5 hours) on the use of analogue models as a bridge to get the general relativity community talking with the condensed matter community.
Jerk, snap, and the cosmological equation of state, 2004.
ASGRG, Australasian Society for General Relativity and Gravitation, Monash, Melbourne, January 2004.Jerk, snap, and the cosmological equation of state, 2003.
SISSA, Trieste, Italy, November 2003.Quantum gravity and random geometry, 2002.
Kolympari, Crete, September 2002.Stephen Hawking 60th Birthday Conference, 2002.
Cambridge University, England, January 2002.Stephen Hawking's "Chronology Protection" conjecture has stimulated considerable research over the last decade  I will give an overview of where we stand. Originally it was hoped that classical or semiclassical physics would be enough to enforce chronology protection, but it is now becoming clear that the full theory of quantum gravity will be needed to provide guaranteed safety.
The book based on this conference was published in October 2003: The future of theoretical physics and cosmology.
Emergent gravity, 2001.
Seminar presented at Victoria University, New Zealand.(A similar seminar was presented at Massey University, New Zealand, in March 2002.)
October 2001.
The idea of modelling (aspects of) Einstein's theory of gravity, by using radically different physical systems that nevertheless share much of the mathematical structure, is attracting a lot of attention. In particular, for any hyperbolic system of PDEs you can use the characteristic curves to define a precursor to the "lightcones" of general relativity, and under suitable algebraic restrictions can then deduce the existence of a pseudoRiemannian metric. I will introduce these ideas, present simple examples, and discuss the extent to which these analog models capture the essence of general relativity.
CPT01 Conference, 2001.
Bloomington, Indiana, August 2001.Acoustic propagation in BoseEinstein condensates has the interesting property that the lowenergy spectrum exhibits an effective Lorentz invariance (in terms of the speed of sound) while at high energies the dispersion relation turns over and becomes Newtonian. }
This very concrete physical model provides an explicit example of a "broken" Lorentz invariance.
Black Holes III Conference, 2001.
Kananaskis, Canada, May 2001.There are numerous different derivations of the Hawking radiation effect. They emphasise different features of the process, and make markedly different physical assumptions  I will present an argument that is "minimalist" and strips the derivation of as much excess baggage as possible. I will argue that all that is really necessary is quantum physics plus a slowly evolving future apparent horizon. In particular, neither the Einstein equations nor black hole entropy are necessary (nor even useful) in deriving Hawking radiation.
Effective geometry, 2000.
A second talk at the Rio workshop: Effective metric describing the Scharnhorst effect.Analog models of general relativity: Introduction and Survey, 2000.
This is the text of the introductory survey lecture I presented at the opening phase of the workshop on "Analog models of General Relativity", held at LAFEX/CBPF (Rio de Janeiro, Brazil) in October 2000.The lecture discusses the various analog models that can be used for modelling kinematic aspects of general relativity: Acoustic black holes, ("dumb holes"), optical black holes, black hole analogs based on BoseEinstein condensates, and "effective geometries" arising from nonlinear electrodynamics.
Abstract:
In this introductory talk I will survey the various "analog models" for general relativity currently being investigated. These analog models include acoustics in flowing fluids, quasiparticles in superfluids, flowing BoseEinstein condensates, slow light, nonlinear electrodynamics, the Scharnhorst effect, and more.
The common theme in all these analog models is the presence of a second "effective" Lorentzian metric that governs the propagation of perturbative fluctuations and/or quasiparticles. This effective metric forces the fluctuations to exhibit many of the kinematic features of general relativity, though dynamic features [those specifically based on the EinsteinHilbert action] typically do not carry over.
It seems plausible that we might be able to construct analog horizons in the laboratory in the not too distant future. Such analog horizons are expected to exhibit Hawking radiation, but possibly without any analog of Bekenstein entropy. Analog models of general relativity are useful probes of Hawking radiation: Because the shortdistance physics is explicitly known (atomic physics), the cutoff is physically understoodthis helps clarify the role of transPlanckian frequencies in general relativity black holes, which in these condensedmatter analogs are replaced by "transBohrian" physics.
The longrange prospects for laboratory investigation of these phenomena is extremely encouraging.
Living on the edge, 2000.
This is the text of a talk I gave at the Astrophysics Institute of Andalusia (Granada, Spain), at SISSA (Trieste), and in shortened form at the Marcel Grossman conference in Rome (July 2000). I talked about brane cosmology: the way in which physicists are trying to model our observable universe as a (3+1) membrane embedded in a higherdimensional spacetime. This talk presents a simple and particularly clean cosmological model based on these ideas and shows how easy it is to get an approximate FriedmannRobertsonWalker universe.Breakthrough Propulsion Physics, 2000.
This is the text of a halfday seminar I gave at the Marshall Spaceflight Center (NASA, Huntsville, Alabama). I talked about some of the peculiar things that happen in general relativity: I also try to make it very clear what current technological limitations are, and why we are *NOT* likely to be building wormholes or warpdrives in the laboratory any time soon.This is a long seminar (three hours) and contains bits and pieces from the other shorter talks presented above. I have not had a chance to upload any of the graphics that accompanied this seminar, so this is text and equations only.
(August 2000)
Twilight for the energy conditions? 2000.
This is the text of a talk I gave at the Marcel Grossman conference in Rome (July 2000). I talked about the energy conditions in General Relativity, what they are, what they are used for, and how easy it is to violate them. The situation is now so bad that it may be time to discard the energy conditions completely. But what should we replace them with?Acoustic Black Holes, 2000.
This is the text of a talk I gave at the University of Mississippi (Ole Miss) on 22 February 2000. I first talk about the deep connection between geometrical acoustics (and geometrical optics) and the pseudoRiemannian (Lorentzian) geometries used in Einstein's theory of gravity (the General Relativity). Then I develop the theme that the connection is even deeper than you might first think, and extends far beyond the realm of geometric acoustics. In particular, you can at least in principle build acoustic analogs of black holes that share many (but not all) of the properties of general relativity black holes  up to and including Hawking radiation but not black hole entropy.Energy conditions, 1999.
This is the text of a talk various versions of which I gave at COSMO99 [Trieste, Italy], the 1999 Midwest Geometry Conference [Columbia, Missouri], the 1999 Midwest Relativity Conference [UrbanaChampaign, Illinois], U Indiana [Bloomington, Indiana], at Purdue U [Fayette, Indiana], and at U Michigan [Ann Arbor]. (1999)Traversable Wormholes, 1999.
This is the text of a colloquium I gave at the University of Maryland. I gave a similar (but less technical) colloquium at the University of Western Illinois. (November 1999)Sonoluminescence, 1999.
This is the text of a seminar I gave at UMSL (U Missouri in Saint Louis), at the University of Maryland, and at the Universidad de Zaragoza, Spain. (November 1999)Talk presented by my collaborator Carmen MolinaParis at the Stochastic Evolutionary Equations Meeting, 1999.
This is the text of a talk presented by Carmen MolinaParis.
It is based on the series of papers concentrating stochastic
differential equations written by a collaboration consisting of David
Hochberg [LAEFF/CAB], Carmen MolinaParis [Los Alamos/LAEFF/CAB], Juan
PerezMercader [LAEFF/CAB], and myself.
14 September 1999.

These technical seminars are supported by FQXi (The Foundational Questions Institute).

Modified gravity; Why and how? [PDF]
Dr Thomas Sotiriou (U Cambridge)

The multiple deaths of Palatini f(R) gravity [PDF]
Dr Thomas Sotiriou (U Cambridge) 
Emergent spacetimes [PDF]
Dr Silke Weinfurtner (UBC Vancouver)

Signature change events: A challenge for quantum gravity? [PDF]
Dr Silke Weinfurtner (UBC Vancouver)

Fuzzy black holes [abstract only]
Dr Elizabeth Winstanley (U Sheffield, UK)
Black hole solutions of the Einstein equations of general relativity have been studied for over 90 years. Traditionally, the simplest types of black hole solutions have been studied, but over the past 20 years there has been an explosion of interest in more complicated black holes which arise when the Einstein equations are coupled to different types of matter field. These more complicated black holes are known as "hairy" black holes. In this talk we describe some black hole solutions of the Einstein equation with a particular type of matter (a YangMills gauge field), in which the black hole solutions can have unlimited amounts of "hair", which we call "furry" black holes.
They are an opportunity for overseas researchers to visit New Zealand and give technical seminars at one or more New Zealand Universities.
More seminars in this series are expected in the future.
Other information:
HomepageVitae
Publications
Book: Lorentzian Wormholesfrom Einstein to Hawking
Horizon: The Time Lords
Some general interest articles
Some graphics
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