This Week in the Universe: October 5th – October 11th

Astrophysics and Gravitation:

Early Universe was Overheated, says NASA

Michael Shull, Kevin France, Charles Danforth, Britton Smith, & Jason Tumlinson (2010). Hubble/COS Observations of the Quasar HE 2347-4342: Probing the Epoch of He II Patchy Reionization at Redshifts z = 2.4-2.9 arXiv arXiv: 1008.2957v1

Credit: NASA/Michael Shull, University of Colorado

From the Press Release:

During a period of universal warming 11 billion years ago, quasars — the brilliant core of active galaxies — produced fierce radiation blasts that stunted the growth of some dwarf galaxies for approximately 500 million years.  This important conclusion comes from a team of astronomers that used the new capabilities of NASA’s Hubble Space Telescope to probe the invisible, remote universe. The team’s results will be published in… The Astrophysical Journal.

For more, see Hubble Astronomers Uncover an Overheated Early Universe.

Dark Matter, Neutron Stars, and Strange Quark Matter, Oh My!

Perez-Garcia, M., Silk, J., & Stone, J. (2010). Dark Matter, Neutron Stars, and Strange Quark Matter Physical Review Letters, 105 (14) DOI: 10.1103/PhysRevLett.105.141101

The abstract:

We show that self-annihilating weakly interacting massive particle (WIMP) dark matter accreted onto neutron stars may provide a mechanism to seed compact objects with long-lived lumps of strange quark matter, or strangelets, for WIMP masses above a few GeV. This effect may trigger a conversion of most of the star into a strange star. We use an energy estimate for the long-lived strangelet based on the Fermi-gas model combined with the MIT bag model to set a new limit on the possible values of the WIMP mass that can be especially relevant for subdominant species of massive neutralinos.

For more, see Does dark matter trigger strange stars?.

High Energy Physics and Particles:

Hey, this isn’t research news!

Yeah, it’s not… But, for anyone who will be in Manchester from October 23rd – 27th, 2010 should make sure they check out Super K Sonic Booooum!

This large installation consists of a 22 meter long ‘river’ of water running through a tunnel lined with thousands of silver balloons (photomultiplier tubes). Members of the public embark on a boat, pulled through the tunnel on a submerged track using a pulley system, with sound and lighting effects, and with an expert particle physicist navigator as a guide. On the journey they learn of neutrinos, their role in the Universe and how scientists detect them. All crew members must first don white Tyvek suits, wellies and hard hats or else face the wrath of Nelly the security chief, at the entrance of the tunnel. This installation is designed to deliver physically thrilling experiences; emerging the audience on a journey through the physics of the Universe.

Workshop on Sunday 24 October – 2pm – 4pm
Capture the Invisible: Craft and Science in particle physics.

In this workshop you will get the chance to make your own photomultiplier tube to capture the invisible in your own bedroom! Designed by Nelly Ben Hayoun in collaboration with Dr Jonathan Perkin, physicist and glassblower Jochen Holz

For more, see Super K Sonic Booooum.

SuperB Project Preparing for Construction!

SuperB Collaboration, E. Grauges et al., Francesco Forti, Blair N. Ratcliff, & David Aston (2010). SuperB Progress Reports — Detector arXiv arXiv: 1007.4241v1

It looks like funding for the SuperB Collaboration will come through and see the new experiment built in Frascati.  I hope the Italians take this great opportunity to make many “flavour country” jokes.

From the press release:

The most elementary components of matter, quarks and leptons, have been found, as the result of 100 years of research, to be organized into three replicating “families”. The reason for this specific number or organization remains a full mystery. Flavor physics, the detailed understanding of the relationship between these families and the comparison between properties of matter and antimatter, is one of the most promising ways to explore new physics, quite complementary to the energy frontier research most notably pursued at the CERN LHC collider. Different kinds of new physics have different effects on rare decays of bottom and charmed quarks and of heavy tau leptons. These particles are all produced at SuperB in unparalleled abundance, making possible for the first time measurements of the precision required to be sensitive to the details of new physics uncovered at CERN.

For more, see SuperB project moves forward, preparing for construction.

Bonner Nuclear Lab to Study Quark-Gluon Plasma

Credit: Frank Geurts/Rice University

It was a good week to get funding for high-energy experiments.

From the Press Release:

Rice University’s Bonner Nuclear Lab has won a $1.175 million grant that will support its research on high-density and hot nuclear matter.  Rice physicist Frank Geurts, who has spent his career looking for clues to the basic elements of the universe by smashing the nuclear contents of gold, lead and other heavy atoms, said the Department of Energy grant will facilitate his group’s transition from constructing and commissioning a highly complex detector system to using that machinery to do basic research.

Video: Quark gluon plasma (QGP)

For more, see Grant advances quark-gluon plasma studies.

General Relativity, Quantum Gravity, et al.:

Curved Space, from the Comfort of Your Home Computer

Gary Felder, & Stephanie Erickson (2010). CurvedLand: An Applet for Illustrating Curved Geometry without Embedding arXiv arXiv: 1010.1426v1

We have written a Java applet to illustrate the meaning of curved geometry. The applet provides a mapping interface similar to MapQuest or Google Maps; features include the ability to navigate through a space and place permanent point objects and/or shapes at arbitrary positions. The underlying two-dimensional space has a constant, positive curvature, which causes the apparent paths and shapes of the objects in the map to appear distorted in ways that change as you view them from different relative angles and distances.

A great, great, Java applet for simulating curved spaces is now online from Erickson and Felder at Smith.  It’s a lot of fun.

For more, see CurvedLand: An Applet to Simulate Curved Space.

Primordial Magnetic Fields and Quasar Axes

Poltis, R., & Stojkovic, D. (2010). Can Primordial Magnetic Fields Seeded by Electroweak Strings Cause an Alignment of Quasar Axes on Cosmological Scales? Physical Review Letters, 105 (16) DOI: 10.1103/PhysRevLett.105.161301

The abstract:

The decay of nontopological electroweak strings may leave an observable imprint in the Universe today in the form of primordial magnetic fields. Protogalaxies preferentially tend to form with their axis of rotation parallel to an external magnetic field, and, moreover, an external magnetic field produces torque which tends to align the galaxy axis with the magnetic field. We demonstrate that the shape of a magnetic field left over from two looped electroweak strings can explain the observed nontrivial alignment of quasar polarization vectors and make predictions for future observations.

For more, see Cracks in the Universe: Physicists are searching for the fingerprints of cosmic strings.

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Not much physics on this turkey

So it’s Canadian Thanksgiving this weekend, and like all good Canadians, I tried to find relevant physics literature to share with the family.  Unfortunately, my colleagues have left this holiday fairly lacking in terms of witty turkey-themed papers and puns.

The best reference I could think of was Robert Laughlin‘s swipe at string theory (which  Mark Twain fans can appreciate).

Robert B. Laughlin, A Different Universe: reinventing physics from the bottom down:

String theory is, in fact, a textbook case of Deceitful Turkey, a beautiful set of ideas that will always remain just barely out of reach.

For some practical physics themed Thanskgiving advice:

Gobble, gobble, gobble?

Weirdly, in Canada, this holiday doesn’t really seem to be about sharing what you’re thankful for, so I’m a little out of practice, but I’d say this Thanksgiving, I’m thankful for WMAP and the almost 10 years it spent giving us amazing insight into the nature of the universe.  You will be missed, WMAP.

I guess I’m also thankful for the fact that today happens to be 10-10-10, (101010 in binary = 42 in base 10), and that’s just cool.

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2010 Nobel Prize in Physics Announced

Press Release, 5 October 2010:

The Royal Swedish Academy of Sciences has decided to award the Nobel Prize in Physics for 2010 to

Andre Geim
University of Manchester, UK


Konstantin Novoselov
University of Manchester, UK

“for groundbreaking experiments regarding the two-dimensional material graphene


In 2000, Andre Geim won the Ig Nobel Prize with Michael Berry “for levitating the frog“.  Winning the Nobel Prize for Physics this year makes him the first person to win an Ig Nobel Prize followed by an actual Nobel Prize.  Kostya Novoselov, at the age of only 36, has ample time to start accumulating prizes.  Interesting, all of the youngest Nobel Prize winners have been in physics: Lawrence Bragg in 1915 at the age of 25, Werner Heisenberg in 1932 at the age of 31, Tsung-Dao Lee in 1957 at the age of 31, Carl D. Anderson in 1936 at the age of 31, and Paul A. M. Dirac in 1933 also at the age of 31.

For more information about the 2010 prizes and to leave congratulations to the winners, visit the Nobel website.

From Geoff Brumfiel:

Andre Geim: “When I got the telephone call, I thought, ‘oh shit!'”

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This Week in the Universe: September 28th – October 4th

Astrophysics and Gravitation:

Vacuum-Driven Evolution in Astrophysics

William C. C. Lima, George E. A. Matsas, & Daniel A. T. Vanzella (2010). Awaking the vacuum in relativistic stars Physical Review Letters arXiv: 1009.1771v1

In a very cool paper that will be appearing in the Physical Review Letters at the end of the week, Lima et al. have shown an interesting (and surprising) relationship between neutron star formation and the vacuum energy density of our universe. Using some semi-classical concepts of gravity [PRL 104, 161102 (2010)], the authors come the conclusion that the formation of relativistic, compact, objects (like neutron stars) could disturb the vacuum of a quantum field (of a certain type) which could cause the energy density of the vacuum to undergo exponential growth.  This growth could eventually lead to the collapse or explosion of the relativistic object in question.  Of course, the observation of stable neutron stars should be suggestive that such fields (that could have triggered this exponential growth in energy density) can not exist.  Thus, if we see stable neutron stars (which we think we do), we learn something about the vacuum state of the universe, ie. the observation of a stable and (reasonably) spinless cold neutron star would rule out the existence of massless scalar fields with a range of coupling constants.  Seeing as we only know what a marginal fraction of the universe’s energy content is, this could prove incredibly useful for the field theoretically inclined cosmologists out there.  The nitty-gritty details on what should specifically happen to these relativistic objects hasn’t been worked out just yet (I’m sure someone will be donating some cluster time soon), but when it has, we may end up learning something new and exciting about one of the most basic aspects of our universe.

For more, see Neutron Star Formation Could Awaken the Vacuum.

High Energy Physics and Particles:

Randomness Brings Order to Quarks

P. H. Damgaard, K. Splittorff, & J. J. M. Verbaarschot (2010). Microscopic Spectrum of the Wilson Dirac Operator arXiv arXiv: 1001.2937v3

An interesting paper out of the Niels Bohr Institute shows how large quantities of random numbers can help explain the oscillations of quarks within protons.

Kim Splittorff:

Over several years it became increasingly clear that the way in which the left-handed and right-handed quarks come together can be described using a massive quantities of random numbers. These random numbers are elements in a matrix, which one may think of as a Soduko filled in at random. In technical jargon these are called Random Matrices.

Random numbers have been used for quite some time to make sense of spontaneous symmetry breaking, but what is unique about this team’s work is that they are doing it exactly.


What is new about our work is that not only the exact equation for quarks, but also the approximation, which researchers who work numerically have to use, can be described using random matrices. It is already extremely surprising that the exact equation shows that the quarks swing by random numbers. It is even more exciting that the approximation used for the equation has a completely analogous description. Having an accurate analytical description available for the numerical simulations is a powerful tool that provides an entirely new understanding of the numerical data. In particular, we can now measure very precisely how closely the right-handed and left-handed quarks are dancing

How “exact” this really can be, is more of a philosophical question at this point, but this technique will find use in helping make predictions at CERN and even in condensed matter systems.

For more, see Quarks ‘swing’ to the tones of random numbers.

General Relativity, Quantum Gravity, et al.:

Hawking Radiation, Observed?

F. Belgiorno, S. L. Cacciatori, M. Clerici, V. Gorini, G. Ortenzi, L. Rizzi, E. Rubino, V. G. Sala, & D. Faccio (2010). Hawking radiation from ultrashort laser pulse filaments arXiv arXiv: 1009.4634v1

I have lengthy comments to make on this paper that will appear later this week, but it is a fascinating (and short) read.

The abstract:

Event horizons of astrophysical black holes and gravitational analogues have been predicted to excite the quantum vacuum and give rise to the emission of quanta, known as Hawking radiation. We experimentally create such a gravitational analogue using ultrashort laser pulse filaments and our measurements demonstrate a spontaneous emission of photons that confirms theoretical predictions.

Did they really observe Hawking radiation? That’s a question that will be open for debate for quite some time.

For more, see Physicists may have observed Hawking radiation for the first time, Imitation black hole seen on earth.

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Georges Charpak (1924 – 2010)

Nobel laureate and experimental high-energy physics pioneer, Georges Charpak, passed away on Tuesday, September 28th, 2010.

Credit: The Nobel Foundation

Fermilab Director, Pier Oddone:

It would be hard to find an experimentalist today who has not used one of Charpak’s inventions.

French President, Nicolas Sarkozy:

[Charpak was a] great humanitarian whose life and commitment are an example for the nation and its youth.

In 1992, Georges Charpak received the Nobel Prize in Physics alone for the “invention and development of particle detectors, in particular the multi-wire proportional chamber (or wire chamber)“.

See his obituary in Fermilab Today.

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This (Long) Week in the Universe: September 16th – September 27th

I know, I know, I switched back to writing these on Mondays again without telling anyone.  It turns out, Wednesdays were a terrible choice of day for me. I swear I asked someone to fill in for me last week…

...but I guess she wasn't all that interested in the job.

Astrophysics and Gravitation:

Taking a Swim in the Lagoon Nebula

Credit: NASA/ESA Hubble Space Telescope

NASA and the ESA Hubble Space Telescope, via the Advanced Camera for Surveys, have provided us with a gorgeous picture of the Lagoon Nebula.  This nebula is of particular interest to amateur astronomers because it is one of only a few of its kind actually visible with the naked eye from Earth.  While it may be a blurry oval to the unassisted human viewer, to Hubble, this gas cloud is a giant, dynamic, home to new stars.  Okay, so there isn’t any new physics here, but they did get a great image.

For more, see Breaking Waves in the Stellar Lagoon.

AGILE on Gamma Rays

Marisaldi, M., et al. (2010). Gamma-Ray Localization of Terrestrial Gamma-Ray Flashes Physical Review Letters, 105 (12) DOI: 10.1103/PhysRevLett.105.128501

A team using satellite data to watch thunderstorms has figured out to to locate gamma rays (sometimes produced in said thunderstorms) with exceptional accuracy.  These models are helping physicists understand gamma rays and how they relate to electrical storms (which most theories wouldn’t actually anticipate).

For more, see Pinpointing Earthly Gamma Rays.

ANITA on Cosmic Rays

S. Hoover, & et al. (2010). Observation of Ultra-high-energy Cosmic Rays with the ANITA Balloon-borne Radio Interferometer Physical Review Letters arXiv: 1005.0035v2

A team using airborne radio detectors has noticed a characteristic radio wave signal produced by ultrahigh energy cosmic rays as they hit the ice in the Antarctic.  Since we still don’t know where these ultrahigh energy particles come from, being able to track them once they hit the earth will be a useful tool in figuring out where they originated from.

For more, see Tuning In to Highest Energy Cosmic Rays.

So Long S-Process

A. J. Gallagher, S. G. Ryan, A. E. García Pérez, & W. Aoki (2010). The barium isotopic mixture for the metal-poor subgiant star HD140283 Astronomy and Astrophysics arXiv: 1008.3541v1

Snipet from the abstract:

Current theory regarding heavy element nucleosynthesis in metal-poor environments states that the r-process would be dominant. The star HD140283 has been the subject of debate after it appeared in some studies to be dominated by the s-process. We provide an independent measure… that observations and analysis do not validate currently accepted theory.

It’s another one of these fun astrophysics mysteries.  We have a reasonable idea how stars work, but every now and then an observation comes along and tells us that our theoretical mechanisms can not be the end all be all of star dynamics and formation.  Star HD140283 is another fun piece to contradictory puzzle.  Because of the suspected age of HD140283 (ie. that it’s very, very old), it should have formed in its galaxy before the first red giants/barium producing stars formed, meaning that it shouldn’t (and according to current theory, couldn’t) have inherited any barium from its neighbours (and thus undergo r-process nucleosynthesis).  However, Gallagher et al.’s team’s observations say otherwise (that instead, we see s-process nucleosynthesis).  Is the current model of star formation incorrect, ie. do we need to rethink this late production of s-process isotope issue? Could there have been barium somehow to kick off this stars life? Could it be something else? Could that star have somehow been pulled in from an older galaxy? At this point, it seems pretty open.

For more, see Ancient star poses galactic puzzle.

High Energy Physics and Particles:

Good news, everyone! We might have been way off about quarks and gluons!

CMS Collaboration (2010). Observation of Long-Range Near-Side Angular Correlations in Proton-Proton Collisions at the LHC JHEP arXiv: 1009.4122v1

So I’m late to the party here, but last week the CMS had some really exciting news: the LHC may have observed some new physics!  Since I missed posting on this last week, I’ll defer to Jon Butterworth (an actual high energy physicist) on the results, hereLuboš Motl has some exciting speculation on what these observations might mean, but expect much more along these lines over the next few months.

For more, see A surprise from the LHC already!, LHC: CMS probably sees quark-gluon plasma or dual QCD string or something better, New two-particle correlations observed in the CMS detector at the LHC.

MiniBooNE Confirms LSND?

Richard Van de Water, A Decade Later: Are We Any Closer to Resolving the LSND Puzzle? GeneFest Symposium, September 25, 2010. PDF of the talk.

Remember those strange Liquid Scintillator Neutrino Detector results from 1997 that suggested some unusual neutrino oscillations inconsistent with the standard model (remember sterile neutrinos?)? Well, MiniBooNE says the LSND results might have been right after all.  The results are still very preliminary and will probably start appearing more and more over the next month, but we may have to give up on three flavours of neutrinos… maybe.

For more, see MiniBooNE at GeneFest 2010.

General Relativity, Quantum Gravity, et al.:

Cosmic nudity

Lehner, L., & Pretorius, F. (2010). Black Strings, Low Viscosity Fluids, and Violation of Cosmic Censorship Physical Review Letters, 105 (10) DOI: 10.1103/PhysRevLett.105.101102

Sure, I mentioned this paper last week, but I’m mentioning it again this week because a) it’s still really cool and possibly very important, and b) the APS did one of their great synopses on it this week.  Check out Cosmic nudity.

Relativity on the Everyday Scale

Chou, C., Hume, D., Rosenband, T., & Wineland, D. (2010). Optical Clocks and Relativity Science, 329 (5999), 1630-1633 DOI: 10.1126/science.1192720

I’m late to the party on this one too, so it’s probably old news by now, but scientists at NIST have done some great “everyday” scale confirmations of relativity: that time passes faster at higher elevations and time passes slowler at higher velocities.  We’ve had experimental confirmation of both of these facts for quite some time, but we’ve never had precise enough clocks to observe their subtle effects at everyday scales (ie. not just from orbit or in a particle accelerator).  The NIST clocks were actually able to see the effect of gravitational time dilation between two surfaces, one just a foot above the other (so yes, time does pass faster if you’re standing on a table versus standing on the floor – Oh no, I live in a high rise apartment! My life is slipping by!). On top of that, so to speak, they also preformed an experiment showing measurable relativistic time dilation when their was only a 20 miles/hour difference between relative moving clocks.  That is mind blowing, because these effects are incredibly subtle and we’d need to live billions of years to actually notice them.  The fact that we can make clocks precise enough to notice them now, is incredible!

For more, see Everything really is relative, Time Dilation in Your Living Room, Revealing, Reveling In Einstein’s Relativity, NIST Pair of Aluminum Atomic Clocks Reveal Einstein’s Relativity at a Personal Scale (press release).

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This Week in the Universe: September 9th – September 15th

Astrophysics and Gravitation:

Astrophysics, by General Mills

Vella, D., & Mahadevan, L. (2005). The “Cheerios effect” American Journal of Physics, 73 (9) DOI: 10.1119/1.1898523

FOX News and a few other news agencies have discovered the Cheerios Effect this week (unfortunately, MSNBC beat them to this scope by about five years).  Back in 2005, Vella and Mehadevan described the “Cheerios Effect”, the tendency for small, wet, objects to attract each other.

From the abstract:

Objects that float at the interface between a liquid and a gas interact because of interfacial deformation and the effect of gravity.

Makes sense, but what does this have to do with astrophysics? Well, just like how the few remaining Cheerios left in the bowl have a tendency to group together in the milk, galaxies have a tendency to group together in space.  While the forces involved are quite different, the outcome is visually rather similar, and, astrophysics has a long history of using fluid models for approximations.  Is this big news? No, but it makes a very good classroom demonstration (as the authors originally wanted).

For more, see Cereal And Saturday Morning Physics.

PAMELA Results on the Cosmic-Ray Antiproton Flux

O. Adriani, & et al. (2010). PAMELA Results on the Cosmic-Ray Antiproton Flux from 60 MeV to 180 GeV in Kinetic Energy Phys. Rev. Lett., 105 (12), 1101-1106 : 10.1103/PhysRevLett.105.121101

The abstract:

The satellite-borne experiment PAMELA has been used to make a new measurement of the cosmic-ray antiproton flux and the antiproton-to-proton flux ratio which extends previously published measurements down to 60 MeV and up to 180 GeV in kinetic energy. During 850 days of data acquisition approximately 1500 antiprotons were observed. The measurements are consistent with purely secondary production of antiprotons in the Galaxy. More precise secondary production models are required for a complete interpretation of the results.

Earlier this year, PAMELA observed an usually large flux of positrons within the cosmic rays they were seeing from some unknown, beyond the atmosphere, source.  Naturally, like all unusual cosmic ray results, people thought “dark matter”.  Now, with more data, the PAMELA team has confirmed these observations, but still can’t suggest a cause.  Observation supports some “secondary production” mechanism for their creation, ie. the positrons being produced by some annihilation interaction with some unknown particles, but it’s still quite open what that might be.

From Tevong You:

Secondary production is referring to predictions of expected antiparticle abundance from models of cosmic rays interacting with interstellar nuclei producing antiparticles from known physics, and the excess or lack thereof is with respect to these models. The positron excess is countered by the antiproton measurement not showing any disagreement with the expectation from secondary production, which is what is being confirmed.

For more, see Uncertain Sources.

Hungry Hungry Stars

Credit: X-ray (NASA/CXC/RIT/J.Kastner et al), Optical (UCO/Lick/STScI/M.Perrin et al); Illustration: NASA/CXC/M.Weiss

NASA’s Chandra X-ray Observatory has recently seen evidence of star cannibalism.  It appears that star BP Piscium (BP Psc – a red giant phase star once probably the size of our Sun) may have absorbed a companion star in the past (or perhaps a large planet).

David Rodriguez from UCLA:

BP Psc shows us that stars like our Sun may live quietly for billions of years, but when they go, they just might take a star or planet or two with them.

For more, see Chandra Finds Evidence for Stellar Cannibalism.

Dark Matter in the Sun (again?)

Lopes, I., & Silk, J. (2010). Neutrino Spectroscopy Can Probe the Dark Matter Content in the Sun Science DOI: 10.1126/science.1196564

From the abstract:

After being gravitationally captured, low mass cold dark matter particles (mass range 5 to ~50 x 109 electron volts) are thought to drift to the center of the Sun and affect its internal structure. Solar neutrinos provide a way to probe the physical processes occurring in the Sun’s core. Solar neutrino spectroscopy, in particular, is expected to measure the neutrino fluxes produced in nuclear reactions in the Sun. Here, we show how the presence of dark matter particles inside the Sun will produce unique neutrino flux distributions…

Ah, more speculation that dark matter could be found inside the sun.  Is this based on observation? Well no, but we still can’t quite explain the expected composition of the sun with its mass and spectrum, so there is room for dark matter.  Is it science? Not yet.

For more, see Searching the Sun for dark matter.

General Relativity, Quantum Gravity, et al.:

Fun with Five-Dimensional Black Strings

Lehner, L., & Pretorius, F. (2010). Black Strings, Low Viscosity Fluids, and Violation of Cosmic Censorship Physical Review Letters, 105 (10) DOI: 10.1103/PhysRevLett.105.101102

The Abstract:

We describe the behavior of 5-dimensional black strings, subject to the Gregory-Laflamme instability. Beyond the linear level, the evolving strings exhibit a rich dynamics, where at intermediate stages the horizon can be described as a sequence of 3-dimensional spherical black holes joined by black string segments. These segments are themselves subject to a Gregory-Laflamme instability, resulting in a self-similar cascade, where ever-smaller satellite black holes form connected by ever-thinner string segments. This behavior is akin to satellite formation in low-viscosity fluid streams subject to the Rayleigh-Plateau instability. The simulation results imply that the string segments will reach zero radius in finite asymptotic time, whence the classical space-time terminates in a naked singularity. Since no fine-tuning is required to excite the instability, this constitutes a generic violation of cosmic censorship.

Video: Frans Pretorius: Apparent horizon embedding diagram of an unstable 5 dimensional black string

Pretorius and Lehner investigate five dimensional black strings to make sense of singularities through quantum gravity.  Through simulation, they showed that black strings evolve into black holes (eventually leading to naked singularities) connected by thin string segments.  If these simulations are correct, it appears we get a violation of cosmic censorship.  A result like this certainly suggests that quantum gravity, formulated along these lines, would lead to violations of causality and a definite change to the causal structure of the universe.  Does this mean that the simulations are wrong or that our notions of causal structure are wrong? At this point, we can’t say either way (and how cool is that?).

For more, see Physicists investigate fate of five-dimensional black strings.

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This Week in the Universe: September 2nd – September 8th

Astrophysics and Gravitation:

What Supernova 1987A Left Behind

France, K., McCray, R., Heng, K., Kirshner, R., Challis, P., Bouchet, P., Crotts, A., Dwek, E., Fransson, C., Garnavich, P., Larsson, J., Lawrence, S., Lundqvist, P., Panagia, N., Pun, C., Smith, N., Sollerman, J., Sonneborn, G., Stocke, J., Wang, L., & Wheeler, J. (2010). Observing Supernova 1987A with the Refurbished Hubble Space Telescope Science DOI: 10.1126/science.1192134

Hubble Video: Supernova 1987A Observed by Hubble from 1994 – 2006

Old data from the Hubble Telescope is shedding new light on the remnants of Supernova 1987A.  It appears that shock waves of gas that were/are being sent out by the supernova core are brightening the ring shaped cloud of dust surrounding it.  It may not add anything critical to our understanding of gravitational collapse, but it makes for pretty visuals.

For more, see ‘Lost years’ end for backyard supernova.

Seeding Magnetic Fields in Spacetime?

Mahajan, S., & Yoshida, Z. (2010). Twisting Space-Time: Relativistic Origin of Seed Magnetic Field and Vorticity Physical Review Letters, 105 (9) DOI: 10.1103/PhysRevLett.105.095005

The Abstract:

We demonstrate that a purely ideal mechanism, originating in the space-time distortion caused by the demands of special relativity, can break the topological constraint (leading to helicity conservation) that would forbid the emergence of a magnetic field (a generalized vorticity) in an ideal nonrelativistic dynamics. The new mechanism, arising from the interaction between the inhomogeneous flow fields and inhomogeneous entropy, is universal and can provide a finite seed even for mildly relativistic flows.

I have to say, this abstract doesn’t make a lot of sense to me, as written.  There is no “spacetime distortion” caused by special relativity, so I’m not entirely sure I understand their meaning here, but let’s address the subject at hand.  In 1979, E.N. Parker wrote a book called “Cosmical Magnetic Fields: Their Origin and Their Activity” in which addressed the issue of, as the title would suggest, cosmic magnetic fields, specifically the generation of said magnetic fields within astronomical bodies.  Then, in 2002, Lawrence Widrow wrote a brief follow up, of sorts, called “Origin of galactic and extragalactic magnetic fields“, where he talks about:

A variety of observations suggest that magnetic fields are present in all galaxies and galaxy clusters… However, fundamental questions concerning the nature of the dynamo as well as the origin of the seed fields necessary to prime it remain unclear.

Finally, in 2008, a fairly comprehensive review paper was written by Kulsrud and Zweibel called, “On the origin of cosmic magnetic fields“, which ends with,

Our conclusion as to the most likely origin of cosmic magnetic fields is that they are first produced at moderate field strengths by primordial mechanisms and then changed and their strength increased to their present value and structure by a galactic disc dynamo. The primordial mechanisms have not yet been seriously developed, and this preliminary amplification of the magnetic fields is still very open.

So this basically brings us to 2010.  In all of the early work on cosmic magnetic field origins, “nonideal mechanisms”, like the baroclinic effect (apparently…), were used to suggest plausible creation or “seed” scenarios for these magnetic fields.  However, the authors of this current paper take a different approach:

[Generalized vorticity] can be generated in strictly ideal dynamics, as long as the dynamics is explicitly embedded in the space-time dictated by the demands of special relativity. The generalized vorticity is, then, generated through a source term born out of the special relativistic ‘‘modifications’’ to the interaction of an inhomogeneous flow with inhomogeneous entropy.

The authors are talking about vorticity instead of magnetism directly because of the “mathematical and dynamical similarity between magnetic fields and fluid vorticity” (it might be a good strategy).  So what are these modifications? Basically, they’re just adding in special relativity to fluid dynamics and drawing an analogy with magnetism.  This has nothing to do with any spacetime distortion (because “spacetime” as a concept only exists in special and general relativity, anyway… so adding special relativity doesn’t “distort” it) or “topology” (the word does appear once in the body of the paper though).

For more, see Origin of magnetic fields may lie in special relativity’s spacetime distortions.

Static Universes Never Die

Well they don’t.

David F. Crawford (2010). Observational evidence favours a static universe arXiv : 1009.0953

Oh good, because enough people aren’t writing about “tired-light cosmology” and “static-universes” these days.  At 42 pages, this bad boy manages to reinterpret all cosmological observations that disprove tired-light and static universe models all the while solving the solar neutrino problem! Happy Day, turns out 1930s astrophysics was right! Oh wait… no, this is just rehashing things that were rejected a long, long time ago.

For more, see Non-Expanding Cosmology Attempts To Oust Big Bang Theory.

High Energy Physics and Particles:

I guess it was a slow week in high energy physics, so I’ll just direct you to high energy physicist Jon Butterworth’s  new blog, “Life and Physics“, hosted by The Guardian.  For more, see: Peter Higgs, UCL and the Right Honorable William Waldegrave.

General Relativity, Quantum Gravity, et al.:

Early Universe was Chaotic?

Katrin Gelfert, & Adilson E. Motter (2010). (Non)Invariance of Dynamical Quantities for Orbit Equivalent Flows Communications in Mathematical Physics : 10.1007/s00220-010-1120-x

Adilson Motter:

According to the classical theory of general relativity, the early universe experienced infinitely many oscillations between contracting and expanding directions… This could mean that the early evolution of the universe, though not necessarily its current state, depended very sensitively on the initial conditions set by the big bang… [W]e have established the conditions under which the indicators of chaos are relativistic invariants.

Sounds good.

For more, see Researchers show that the big bang was followed by chaos.

Spacetime is 2D… on Quantum Gravity Scales

Steven Carlip (2010). The Small Scale Structure of Spacetime arXiv arXiv: 1009.1136v1

It’s generally believed by theorists that, on small scales, spacetime is effectively two-dimensional.  Why this is, is still mystery, like much of quantum gravity, but the issues are starting to become better understood.

From the abstract:

I summarize the evidence for such “spontaneous dimensional reduction,” and suggest an additional argument coming from the strong-coupling limit of the Wheeler-DeWitt equation. If this description proves to be correct, it suggests a fascinating relationship between small-scale quantum spacetime and the behavior of cosmologies near an asymptotically silent singularity.

It’s a very good review paper (plus some new insights), so it’s worth the read.

For more, see Why Spacetime on the Tiniest Scale May Be Two-Dimensional.

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Good News: Exemptions for natural scientists to the Ontario Engineers Act

There is good news this evening for Canadian scientists who were worried about the Ontario Engineers Act! The natural science societies (Canadian Association of Physicists, Association of the Chemical Profession of Ontario, Canadian Astronomical Society, Canadian Meteorological and Oceanographic Society, Canadian Organization of Medical Physicists, Canadian Society for Chemistry, and Chemical Institute of Canada) have come to a tentative agreement with the Professional Engineers of Ontario (PEO) and the Attorney General’s Office, for an exemption to the Ontario Engineers Act for natural scientists working in Ontario.  The following communique is going out to all society members:

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Changes to Ontario Engineers Act could put Canadian scientists out of work

I am reproducing a letter that I received from the Canadian Association of Physicists today.  This isn’t something that I would normally do, but it’s actually a very important and pressing issue that will effect scientists, specifically physicists, across Canada.

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