It's tradition for various science media outlets to publish their lists of biggest scientific breakthroughs of the year right about now. And no doubt those breakthroughs deserve the attention and acclaim. But let's face it, most scientific papers don't get lauded as major breakthroughs; science progresses incrementally. We at the cocktail party think such papers nonetheless hold their own fascination, and are worthy of some year-end recognition all their own. So Jen-Luc Piquant has compiled her 20 favorite physics papers of 2014, ranging from the sublime to the downright silly.
1. BICEP2 Announces Direct Evidence of Gravitational Waves in Polarization Data from the Cosmic Microwave Background Radiation. Yeah, okay, this qualified as a Very Big Deal by any objective measure -- the ensuing controversy means it likely won't top many Breakthrough of the Year lists, but it was certainly the biggest physics story of the year. The big announcement was made in March. The backlash and questioning of the BICEP2 results set in within a couple of weeks, and kept building until the Planck collaboration released some intermediate results this fall. Researchers on the Planck mission say galactic dust could fully explain the much-ballyhooed observation announced to great acclaim in March — or at least part of the possible signal that BICEP2 claimed was evidence for cosmic inflation. The final verdict is not yet in, and honestly, it's not looking promising for BICEP2, but there's no denying the impact of the BICEP2 and Planck papers, both in terms of headline-grabbing media and in igniting intense scientific debate. BICEP2 I: Detection Of B-mode Polarization at Degree Angular Scales. BICEP2 II: Experiment and Three-Year Data Set. Planck intermediate results paper: The angular power spectrum of polarized dust emission at intermediate and high Galactic latitudes.
2. Physicists Produce Quantum Version of the Cheshire Cat, which is a clever way of saying that they separated a neutron from its property of magnetism. Per Science magazine: "The experiment is the latest example of how quantum mechanics becomes even weirder using a technique called weak measurement and could provide researchers with an odd new experimental tool for performing precision measurements." Paper: Observation of a quantum Cheshire Cat in a matter wave interferometer experiment.
3. Schrödinger’s Picture: Researchers Take An Image Without Ever Detecting Light. Per New Scientist: “These images were generated using a cat stencil and entangled photons. The really spooky part is that the photons used to generate the image never interacted with the stencil, while the photons that illuminated the stencil were never seen by the camera.” Nature paper: Quantum imaging with undetected photons.
4. Quantum Mechanics from a Classical Multiverse: Many Interacting Worlds. Per Physics Buzz: “In a paper published in Physical Review X, physicists Michael Hall, Dirk-André Deckert, and Howard M. Wiseman have proposed a new view of quantum mechanics that may be testable in a way that could prove that it alone is the correct interpretation. They call it the Many Interacting Worlds approach to quantum mechanics.” Another physicist who's been thinking along those lines is philosopher of physics grad student Chip Sebans, who wrote a guest blog post at Preposterous Universe about his own work in this area; his paper is pending publication in Philosophy of Science. Physical Review X paper: Quantum Phenomena Modeled by Interactions between Many Classical Worlds. Philosophy of Science (on arxiv) paper: Quantum Mechanics as Classical Physics.
5. Physicists sound-out acoustic tractor beam that can pull an object by firing sound waves at it. Per Physics World: "The new tractor beam has been created by Mike MacDonald and colleagues at the University of Dundee, University of Southampton and Illinois Wesleyan University by using an ultrasound ablation system, which is normally used to destroy tumours thanks to focused beams of intense sound. First proposed in 2006 by Philip Marston of Washington State University and realized using light in 2010 by David Grier and colleagues at New York University, the technique involves firing two beams of ultrasonic waves upwards at a triangular-shaped target at about 51° either side from the vertical direction. The target is shaped such that the beams bounce off opposite sides of the triangle, causing the reflected sound to travel straight up." Physical Review Letters paper: Acoustic Tractor Beam.
6. Lasers Ignite Supernovae in the Lab. Per Physics World: "The researchers used the Vulcan laser facility at the Rutherford Appleton Laboratory to recreate their SNRs. "Our team began by focusing three laser beams onto a carbon-rod target, not much thicker than a strand of hair, in a low-density gas-filled chamber," says Jena Meinecke, an Oxford University graduate student who headed the experiment. When the rod is heated to a temperature of a few million degrees kelvin, it explodes. This creates an asymmetric shock wave that expands outwards through the argon gas, much like a real supernova in space." Paper in Nature Physics: Turbulent amplification of magnetic fields in laboratory laser-produced shock waves.
7. The Return of Louis de Broglie's pilot waves! Fluid Tests Hint at Concrete Quantum Reality: A droplet bouncing on surface of a liquid exhibits quantum-like properties, including double-slit interference, tunneling and energy quantization, according to a review article appearing in the Annual Review of Fluid Mechanics exploring "the connection between Couder’s fluidic system and the quantum pilot-wave theories proposed by de Broglie and others," per Nanowerk News. (I wrote about this for the NOVA Nature of Reality blog.) Annual Review of Fluid Mechanics paper: Pilot wave hydrodynamics.
8. The Dawn of the Tetraquark, a negatively charged particle roughly 4.7 times more massive than a proton, made some waves when it was first observed on April 9, 2014, at the Large Hadron Collider. It's been dubbed Z(4430)− because physicists suck at naming things. And this surprising Quark Quartet Fueled a Quantum Feud: The newly discovered particles incited a fierce debate among experts about the correct picture of matter at the quantum scale. “We hate each other,” Antonio Polosa, a theorist at Sapienza University of Rome, told Quanta, chuckling about the rival factions. “We really hate each other.” Physical Review Letters paper: Observation of the Resonant Character of the Z(4430)− State.
Addendum, 12/17/14 8:24 PM PST: My wording in the above item is a bit misleading. The Z(4430) peak was actually first observed with a significance of 6.5 sigma by the Belle Collaboration in 2007 at the KEKB collider in Tsukuba, Japan. (See arXiv:0708.1790.) Per Adam Morris of the University of Edinburgh, "What we did at LHCb was confirm that this structure really is a resonance in the psi(2S)pi spectrum: i.e. that it is indeed a bound state of ccdu quarks. Our measurement of spin and parity also disfavours models such as mesonic molecules or threshold effects, leaving the tetraquark interpretation as being the most likely."
9. Wakefield Particle Accelerators on a Tabletop achieve new world record for compact particle accelerator, which means that Cheap Compact Particle Accelerators May Be Our Physics Future. "This result requires exquisite control over the laser and the plasma," Dr. Wim Leemans, the director of the lab's Applied Physics Division, explained in a press release. To wit: "a pulse of laser light is injected into a short and thin straw-like tube that contains plasma. The laser creates a channel through the plasma as well as waves that trap free electrons and accelerate them to high energies. It's similar to the way that a surfer gains speed when skimming down the face of a wave." Physical Review Letters paper: Multi-GeV Electron Beams from Capillary-Discharge-Guided Subpetawatt Laser Pulses in the Self-Trapping Regime.
10. Scientists at University of Göttingen and the Institut Laue Langevin Come Up With Ice XVI, A New Form Of Ice. Per io9: "It consists of frozen water molecules spun into a tiny, intricate, empty cage. Here's How they made it. The structure already existed. The trouble was that structure was wrapped around other atoms in a configuration too fragile to be untangled. The water, combined with its various atoms, formed a clathrate. A clathrate is simply a lattice or crystal structure. A clathrate hydrate is such a structure formed by water. Its "guest molecules" could be anything, from methane to carbon dioxide. Try to take them away, and study the lattice by itself, and the clathrate collapses. To part the clathrate hydrate and its guests, scientists went low-tech. They used a simple vacuum pump, coupled with very low temperatures. Their inspired move was their choice of guest molecules. Neon atoms are comparatively small and footloose. When exposed to a vacuum, they can slowly be drawn out of the cage without damaging its structure. What's left is a water clathrate without a guest, or ice XVI." Nature paper: Formation and properties of ice XVI obtained by emptying a type sII clathrate hydrate.
11. Turbulent black holes grow fractal skins as they feed. “We showed that when you throw stuff into a black hole, the surface of the black hole responds like a fluid – and in particular, it can become turbulent,” Allan Adams at the Massachusetts Institute of Technology, told New Scientist. “More precisely, the horizon itself becomes a fractal.” Physical Review Letters paper: Holographic Turbulence.
12. The Physics of Sticky Gecko Feet. What gives geckos the remarkable ability to run upside down across ceilings and stop short on smooth vertical surfaces? Funky toe hairs allow geckos to turn stickiness on and off. (Needless to say, Funky Gecko Toe Hairs is the name of Jen-Luc Piquant’s next band.) The Los Angeles Times says you could call it “the hierarchy of hairs.” Journal of Applied Physics paper: Role of seta angle and flexibility in the gecko adhesion mechanism.
13. New Paper Explains How To Make Supermaterial Graphene In A Blender. To wit, per Nature News: Place 0.5 l water, 10-25 ml detergent, 20-50 g graphite in 400W blender, and run 10-30 min. Nature paper: Scalable production of large quantities of defect-free few-layer graphene by shear exfoliation in liquids.
14. The Physics of Diving Peregrine Falcons. Per PLOS Blogs: “By combining their wind tunnel analysis with the data from the video footage, the researchers created the most comprehensive analysis of a peregrine falcon dive to date, including factors such as lift, drag, acceleration, and trajectory.” PLoS ONE paper: Diving-Flight Aerodynamics of a Peregrine Falcon (Falco peregrinus).
15. Insect Swarms Go Supercritical. Per Motherboard: "Swarms of insects and birds behave in very similar ways to a realm of physics in which the phases of matter—solids, liquids, and gases—cease to exist. It’s here, near what’s known as the critical point, that very slight perturbations are able to extend instantaneously across vast collections of particles and, likewise, across entire flocks and swarms." Physical Review Letters paper: Finite-Size Scaling as a Way to Probe Near-Criticality in Natural Swarms.
16. Physics Meets History: I had a feature in New Scientist (subscription required) on an intriguing collaboration between a complexity scientist and a digital historian to analyze the digitized archives of London’s Old Bailey courthouse that revealed our changing attitudes to violent crime -- going back to an era when theft was worse than murder. The paper was also covered by the New York Times and Nautilus, with the latter also featuring a video Q&A with co-author Simon Dedeo. PNAS paper: The civilizing process in London’s Old Bailey.
17. Experiments in virtual world Second Life Reveal Alternative Laws of Physics, allowing researchers like Renato dos Santos at the Lutheran University of Brazil in Canoas to experiment with entirely different laws of motion. Per Technology Review: "He points out that the world has some relatively complex laws to govern the weather and the rising and setting of the Sun. 'The Second Life Sun usually rises and sets each four Earth hours always directly opposite a full Moon,' he says. And the servers compute a simplified solution of the Navier-Stokes equations to simulate the motion of winds and clouds that time-evolve across the entire world." Paper: Second Life as a Platform for Physics Simulations and Microworlds: An Evaluation. You can see videos of two simulations here: The Buridanian Cannon, in which simulated bullets reproduce the path predicted by Buridan's Theory of Impetus (below), and a Lander Simulator.
18. Mean Jerk Time: There’s an Equation for That, with "that" being what io9 called The Greatest, Most Scientifically Accurate Dick Joke Of All Time, courtesy of a particular raunchy scene in the HBO series Silicon Valley that captures the testosterone-fueled culture of the tech industry perfectly. Embedding has been disabled but you can watch the (very, very NSFW) clip here. The infamous scene inspired a 12-page report written by Stanford researchers Dinesh Chugtai and Bertram Gilfoyle, who explained:
"A probabilistic model is introduced for the problem of stimulating a large male audience. Double jerking is considered, in which two shafts may be stimulated with a single hand. Both tip-to-tip and shaft-to-shaft configurations of audience members are analyzed. We demonstrate that pre-sorting members of the audience according to both shaft girth and leg length allows for more efficient stimulation. Simulations establish steady rates of stimulation even as the variance of certain parameters is allowed to grow, whereas naive unsorted schemes have increasingly flaccid performance."
Paper: Optimal Tip-to-Tip Efficiency: A [Probabilistic] Model for Male Audience Stimulation. The opening line: “Assume a large presentation hall with at least one aisle.”
19. Astronomers Publish Study On Extraterrestrial Zombies. Per io9: “[T]wo astronomers have performed a genuine public service for Earth by calculating the likely number of nearby planets inhabited by the undead.... Further information is available at the newly established SETZ Institute.” Necronomicon paper: A Necro-Biological Explanation for the Fermi Paradox.
20. A Mathematical Model of Pride and Prejudice. Oh, those catastrophic bifurcations! They are the scourge of lovers everywhere. Per Discover's Seriously Science blog: “The analysis shows that the story is characterized by a sudden explosion of sentimental involvements, revealed by the existence of a saddle-node bifurcation in the model. The paper is interesting not only because it deals for the first time with catastrophic bifurcations in romantic relation-ships, but also because it enriches the list of examples in which love stories are described through ordinary differential equations.” Paper in Nonlinear Dynamics Psychological Life Science: A Mathematical Model of Pride and Prejudice.