New 3-Body Orbits Discovered

LY12833 - Predicting the general motion of three celestial bodies, such as planets, or stars, mutually interacting by Newtonian gravity is among the longest standing problems in physics. It was shown by Bruns in 1887 that the three-body problem is not solvable in its most general form, the way the two-body problem is. Over time, three families of particular solutions, realizable under specific conditions, have been discovered, however. All trajectories in these three families share the same geometrical and algebraic symmetries, thus defining a single class.

In this work, we report the discovery of 13 additional distinct families of possible three-body trajectories. Besides three new families belonging to the one previously known class, 10 families belong to three new classes. These three new classes of trajectories represent hitherto unprecedented, and even undreamt of types of planetary motion. While this still leaves the three-body problem unsolvable in general, our findings significantly contribute to the understanding of celestial mechanics and planetary motion.

Historically, the first family was found using only pen-and-paper by the great 18th century mathematicians Leonhard Euler and Joseph Louis Lagrange. Then, in the mid-1970's, the late NASA scientist Roger Broucke and the French astronomer Michel Henon discovered the second family using electronic computers. These computers were among the largest available at the time, but their power was smaller than that of today's mobile phones. The first member of the third family was found by the New Mexico-based computer scientist and physicist Cris Moore in 1993, and is now known as the "figure-8" trajectory. Further members of this family were found between years 2000 and 2005.

Are We Part of a Universe or a Multiverse?

LN13276DR - Can we verify that our Universe is part of a larger Multiverse?  Almost a century ago scientists debated whether the spiral nebulae, what we we now know to be spiral galaxies, were distinct "island universes" of stars apart from our own Milky Way galaxy.  We now understand the Milky Way is but one galaxy in a Universe filled with other galaxies.  Could our entire Universe be encapsulated in but one of many cosmic bubbles in a dynamic Multiverse?  In this paper, we predict detailed and potentially observable signals resulting from a collision in the Multiverse between two cosmic bubbles ---  our Universe and another bubble universe.  Each collision produces a special wave, a cosmic wake, that travels across the Universe from the time of the big bang leaving imprints in the cosmic microwave background (CMB) and large scale distribution of galaxies.  This cosmic wake picks out a special direction on the sky and, we predict, will leave a heretofore unknown highly characteristic "double ring" structure in maps of CMB polarization.  Detection of such a signal would constitute a truly Copernican shift both in fundamental physics and in humanity's view of the what the cosmos is.  Our work goes to the heart of the questions asked by so many about our place in the Universe, but returns quantitative and testable predictions.  Data from next-generation CMB experiments, including the soon-to-be-released data from the ESA/NASA Planck mission, have the potential to uncover the imprints of cosmic bubble collisions. 

Teleportation goes relativistic

LZ12888 - How do motion and gravity affect quantum information tasks? In 2012 a teleportation protocol was successfully performed across 143km between two Canary Islands by A. Zeilinger’s group. In this experiment,  time and positions were determined accurately employing the Global Positioning System (GPS), which is a system of satellites used for time dissemination and navigation. It is well known that GPS takes into account Einstein's theory of relativity to achieve the required precision. However, relativistic effects over the basic resource of the experiment -quantum entanglement- were not considered. Motivated by the success of this kind of tests, space agencies are investing resources for the implementation of space-based quantum communications. At these regimes, relativistic effects can no longer be ignored. In our Letter, we show that relativistic motion and gravity have observable effects in the quantum teleportation protocol. Indeed they can decrease its efficiency; however, we explain how the errors can be corrected. We propose a physical implementation of our relativistic teleportation protocol, which is well within reach of cutting-edge technology using superconducting circuits. The realization of this low-cost tabletop experiment, demonstrating for the first time the effects of relativity on quantum information tasks, will inform expensive space-based programs.

Forming Black Holes From Colliding Particles

LX12835 - This work shows that particles colliding at near the speed of light not only can create black holes, but that they can do so by acting like a gravitational version of a lens.  There was a lot of controversy a few years ago over the possibility that the Large Hadron Collider might create tiny black holes by smashing particles together at high speeds; however the details of how such collisions would unfold remain poorly understood.  In this work, computer simulations of Einstein's theory of gravity are used to study collisions of fluid particles at higher speeds than previously explored.  It is found that black holes can actually form at lower energies than expected, seemingly because the colliding particles act like gravitational lenses, with each particle focusing the energy of the other.  This focusing can concentrate enough energy in a small enough region to warp space and time, creating black holes.

Biogenic crust dynamics on sand dunes

LU13310ER - Sand dunes are often covered by vegetation and biogenic crusts. Despite their significant role in dune stabilization, biogenic crusts have rarely been considered in model studies of dune dynamics.  Using a simple model, we study the existence and stability ranges of different dune-cover states along gradients of rainfall and wind power. Two ranges of alternative stable states are identified: fixed crusted dunes and fixed vegetated dunes at low wind power, and fixed vegetated dunes and active dunes at high wind power. These results suggest a cross-over between two different forms of desertification.

On perpetual motion of the fourth kind

Physical Review D: According to Webster's Dictionary, the perpetual motion is "motion that continues indefinitely without any external source of energy; impossible in practice because of friction". In our paper, contrary to this would-be-obvious statement, we propose an explicit construction of a perpetually moving (rotating) device. Counterintuitively, the proposed device is a solid one-piece object which has no internally moving mechanical parts. Surprisingly, the perpetual rotation of the device is literally driven by zero-point vacuum fluctuations. The device does not produce any work despite the fact that its equilibrium ground state corresponds to a permanent rotation (the device would rotate forever if even it is immersed in a gas). The existence of such device is consistent with all laws of thermodynamics as is proven in the paper explicitly. Intriguingly, the proposed device has an extremely simple construction which is analogous  to the one of certain metamaterials (the latter are used in design of invisibility cloaks, which are also science-fiction-like, but, nevertheless, real physical objects). We point out that the proposed device -- which we call as the perpetuum mobile of the fourth kind -- may possibly be engineered using carbon nanotubes. We stress that the device cannot be used to produce energy from nothing (no existing conservation and/or thermodynamics laws are violated). Summarising, we have proposed a solid one-piece object which rotates forever in its lowest energy state, being driven by zero-point vacuum fluctuations.

Do molecules have intelligence of their own?

LY13069 - Despite the fact that the molecular complementarity and recognition concepts, used to explain the association between macromolecules, which in turn plays an important role in many biological and supramolecular chemistry systems, the underlying molecular mechanism is still not well understood. These concepts suggest that the macromolecules have information of each other, and hence some kind of intelligence, that, on the other hand, we know they do not posses. We show that the union of macromolecules (in a solvent solution), is favored, not by macromolecular recognition, but by the migration of the solvent particles, from their confined position in-between the macromolecules, to the rest of the fluid.

A New Cosmic Measuring Stick: Unusually bright type 1a Supernovae

LY13449 - White dwarfs are formed when stars exhaust their nuclear fuel. In this letter, we establish a new upper mass limit of 2.58 solar mass for white dwarfs. This is remarkably deviated from the famous Chandrasekhar's mass limit of 1.44 solar mass. Our result, unlike Chandrasekhar's, is based on the evolution of magnetic field in white dwarfs. This solves the origin of puzzling, unconventional, over-luminous, type Ia supernovae (explosions of white dwarfs), which must have super-Chandrasekhar mass white dwarfs as progenitors, contrary to those having the conventional Chandrasekhar mass. The characteristic nature of luminosity variation with time of type Ia supernovae allows them to be used as a 'standard' for measuring far away distances (standard candle) and understanding the expansion history of the universe. Applying this idea to conventional type Ia supernovae led to the Nobel Prize in Physics in 2011 for the discovery of the accelerating universe. Our discovery, however, more than 80 years after the proposal of Chandrasekhar mass limit, heralds the onset of a paradigm shift, plausibly leading to establish the unconventional supernovae as new standard candles for cosmic distance measurement.

Collective phenomena in Wikipedia: Cooperation and conflict

LU13814 - The process of conflict resolution in Wikipedia, an iconic, collaboratively edited encyclopedia, is described as the result of the competition between direct interactions among editors and their interactions with a globally shared medium, such as a Wikipedia article. Darwin himself wondered on the origin of the noble virtue of human cooperation being difficult to explain by natural selection. Today, information-communication technology has opened up unprecedented opportunities of solving complex tasks as a collective emergent phenomenon involving the cooperation of many individuals across the world. This has enabled such collaborative projects like open software development or the CERN experiments. While this leads to a higher level of synergy, unavoidably conflicts of diverse opinions are generated, signalled in Wikipedia by an unusually high number of edits in an article. Our model of how Wikipedia works reproduces key stylized features of conflict dynamics observed in real-world Wikipedia articles. For example, with a fixed number of editors forming one 'mainstream' and two opposing 'extremist' groups, consensus in the medium's content is only achieved after a long time and it may not correspond to the initial mainstream view. In the case of a dynamic environment where new editors replace older ones, periods of conflict and consensus can alternate indefinitely, depending on the rate of newcomers and the degree of controversy in the article's topic. The understanding of these mechanisms provided by our model opens the way for the improvement of the conditions for value production in collaborative environments.

Cell shape is the key to understanding blood vessel formation

LX13714E - Blood vessel formation is an important process during development, regeneration and disease. Networks of blood vessels are formed by cells that move around and interact with one another. By computationally modeling this collective behavior of cells we show that long, adhesive cells form networks without any long distance forces and we explain how this happens. In experiments, living cells are seeded on a medium, upon which they elongate and form a network that is similar to the networks formed by our model. This network formation has been attributed to long distance forces, either via chemicals secreted by the cells or mechanical forces conducted by the medium. We now show that long cells form groups of aligned cells. When these groups meet they do not merge but form a branch point and in this manner a network is formed. Earlier studies showed that cell elongation is important in network formation; our work explains how cell elongation helps network formation. Furthermore we show that long distance forces are not necessary, although they may act to stabilize the networks. These new insights can help to interpret experimental results and thus benefit the overall understanding of blood vessel formation.

Optimizing Energy Efficiency with Solid State Thermoelectric Devices

LY13235 - Conservation laws are certainly one of the most elementary and fundamental principles of mechanics. The surprise is that they may play a basic role to solve one of the main problems of future society. Providing a sustainable supply of energy to the world’s population will become a major societal problem for the 21^st century. Thermoelectric phenomena provide a method for heating and cooling,  with no moving parts, possible miniaturization  and absence of emission. They could play a crucial role in a global sustainable energy solution but the  main problem is that in spite of 60 years of research, the efficiency of thermoelectric devices is too low. A breakthrough - allowing increase of efficiency- would have a substantial economic and environmental relevance. In  this letter  we show that total momentum conservation property allows thermoelectric efficiency to reach the ideal Carnot limit.

Engineering a Light Touch

LY13471 - Researchers have found a way to enhance the force of light on matter. Most of the time the momentum of light and the associated forces are too small to notice, but at the nanoscale the effect can be quite large, and researchers have used these forces to dynamically manipulate optical waveguides at the nanoscale. However, these optical forces decay significantly as the distance between the waveguides increases and become too small for all-optical device actuation at larger separation distances.

The new method amplifies the optical forces and thus extends them to larger separations between waveguides by using a novel way to alter the perceived distance between them. This is done with thin layers of engineered structures known as metamaterials, which can manipulate light in ways not seen in conventional materials, extending its influence to greater distances from the surfaces of the waveguide. This work paves the way for the production of optical forces with unprecedented amplitude and eventually the design of mechanical devices activated entirely by light.

Higgs Discovery Points to New Fundamental Constant

LY12930 - The discovery of the Higgs boson at the CERN Large Hadron Collider last year has deep implications for gravitational theories that explain the evolution of our universe. Indeed, the Higgs boson can couple to the gravitational field in a very unique way. This implies the existence of a new fundamental coupling constant in nature, which could be significant, for example, for cosmic inflation. In a paper to appear in the Physical Review Letters, physicists show that the recent discovery at CERN enables us to set the first bound ever on the magnitude of this new parameter of nature. Measuring the coupling of the Higgs boson to the gravitational field with precision ought to have deep implications for the unification of gravity and quantum mechanics and help to fulfill Einstein’s dream.

Contrarian Physics

LR13697E - The allocation of resources is a fundamental issue all species or human beings are facing in their daily life. In order to survive and develop, they must compete against others for sharing such resources by using various strategies. One of the strategies is contrarian behavior. Here we report the existence of a phase transition in a class of well-regulated resource-allocation systems with contrarian behavior by using human experiments, computer simulations, and theoretical analysis. The phase transition allows us to reveal the positive role and the negative role of contrarian behavior. This finding is in contrast to the popular belief that contrarian behavior always has a positive role in resource allocation. This work is of value for various kinds of resource-allocation-related human activities like stock-trading, gambling, travelling, driving, etc.

Centipede Locomotion

LE13747E - Centipedes have many body segments and legs and they generate body undulations during terrestrial locomotion. Centipede locomotion has the characteristic that body undulations are absent at low speeds, but appear at faster speeds; furthermore, their amplitude and wavelength increase with increasing speed. There are conflicting reports regarding whether the muscles along the body axis resist or support these body undulations and the underlying mechanisms responsible for the body undulations remain largely unclear. In the present study, we investigated centipede locomotion dynamics using computer simulation with a body mechanical model and experiment with a robot and then conducted dynamic analysis with a simple model to clarify the mechanism. The results reveal that body undulations in these models occur due to an instability caused by a supercritical Hopf bifurcation. We subsequently compared these results with data obtained using actual centipedes. The model and actual centipedes exhibit similar dynamic properties, despite centipedes being complex, nonlinear dynamic systems. Based on our findings, we propose a possible passive mechanism for body undulations in centipedes, similar to a follower-force or jackknife instability. We also discuss the roles of the muscles along the body axis in generating body undulations in terms of our physical model.

Flowing Grains in Zero-G

LU14260 - Granular materials are ubiquitous in nature and industry. Typical examples are sand on the beach, a drug powder at a pharmaceutical plant, and even the dust and soil covering the surfaces of planets, satellites and small bodies of our Solar System. While flows of granular materials are often studied, a complete set of equations governing these flows is still undiscovered.  In other words, the power to predict granular flows is often faced with large uncertainties despite the existing efforts made to develop sophisticated models.  As an example, little is known about the role of gravity in these flows, as gravity is fixed on Earth, while it is much smaller on celestial bodies such as asteroids, and even on the Moon or Mars.  By using the unique gravitational environment available onboard the Zero-G aircraft, we have performed experiments to investigate the role of gravity in a granular flow. This allows us to explore the behavior of granular material in conditions that become very close to the ones encountered on the surface of much smaller bodies than the Earth.   In normal gravity the flow has two components: the bulk flow that we induce, and a secondary “convective-like” flow. The characteristics of convective-like flows are crucial in industrial applications such as segregation by size, shape, and density, as well as astrophysical questions, such as understanding the behavior of soil on planetary surfaces. We find the secondary flow is suppressed in zero gravity, and enhanced in high gravity. We suggest that gravity tunes the frictional particle-particle and particle-wall interactions that drive the convective-like flow, and present measurements to support this. Such an understanding of the role of gravity is important to interpret the images of granular surfaces sent by space missions visiting other solid bodies of our solar system and to prepare future missions – robotic or manned – which will interact with those surfaces.

How stone monuments deteriorate in the presence of salts

LU13997 - Crystallization in confined spaces, such as pores, is relevant to nearly every field of science. Salts crystallizing within porous materials exert a pressure that contributes to damage, but the quantification of this in-pore pressure is very difficult to achieve. Salt-induced physical weathering has been documented as a substantial damage mechanism in nearly every environment all over the world from pharaoh’s tombs in Egypt, the cathedrals of Europe, decorated caves in China, Mayan pyramids in Mexico and Central America and historic buildings in the United States and England. In this paper, we calculate the solution supersaturation and resulting crystallization pressure and unequivocally identify the precipitating phase in a multi-phase salt system (containing hydrous and anhydrous, metastable and stable phases). These results help to explain why salts, such as Na2SO4 with various hydrated phases are more damaging than single phase salts such as NaCl. We also show that damage associated with meta-stable phase transitions can be suppressed by the use of crystallization promoters. These results point to new ways to prevent salt damage to building materials by bypassing metastable phase formation.

Understanding astrophysical jets with magnetized laser experiments

LX13024 - Objects as diverse as proto-stars, dying-stars and black-holes eject  powerful beams of matter (jets) that are believed to be shaped by magnetic fields. In this letter we show how their formation can be studied in the laboratory by coupling high-power lasers with magnetic fields. In the proposed experiments, an intense laser source irradiates a thin-foil generating a spherically expanding, million-degrees plasma. By imposing a strong magnetic field, this flow can be shaped into an elongated, drop-like bubble which generates a centimetre-long  jet propagating at more than 300 km/s. We speculate that astrophysical jets may be similarly produced from stellar winds expanding in a magnetic field.

Physical Limits to Leaf Size in Tall Trees

LV13534 - Leaf size in angiosperm trees vary by more than three orders of magnitude, from a few millimeters to over 1 meter. This large morphological freedom is, however, only expressed in small trees and the observed leaf size range declines with tree height, forming well-defined upper and lower boundaries. The vascular system of tall trees that distributes the products of photosynthesis connects distal arts of the plant and forms one of the largest known continuous microfluidic distribution networks. In biological systems, intrinsic properties of vascular systems are known to constrain the morphological freedom of the organism. We show that the limits to leaf size can be understood by physical constraints imposed by intrinsic properties of the carbohydrate transport network. The lower boundary is set by a minimum energy flux, the upper boundary by a diminishing gain in transport efficiency.

Cooling by Heating

PRX - When a bulk piece of material is heated at its surface, does its center become hotter or cooler? It turns out that the answer to this seemingly banal question is not obvious at all at a fundamental level. In this paper, we report, first through a theoretical analysis and prediction and then with experimental confirmation, an extraordinary phenomenon of cooling at the center of a supercooled liquid drop heated at its free surface.

Friends of friends key to job and mate searches

Physical Review E - Imagine that you are searching for a job, a date or an expert opinion on a social network. What do you do? Until recently, you had to rely on your friends or acquaintances, but nowadays, using social network sites (like Facebook, Twitter or LinkedIn) you can go beyond that and start to search not only using your direct friends but also the friends of your friends, or the friends of your friends of your friends, and so on. That is, you can find out not only people that is one degree of separation from you in the social network, but people that is two or three degrees from you on the social network. Since, we live in a small world perhaps with only six degrees we can span the whole network. In a recent paper, published on November 19 in Physical Review E, researchers found a navigation strategy that does precisely that: to jump directly to more than one degree of separation on a network. They found that this strategy, named Levy walks, akin to the one used by foraging animals, can be very efficient to search and navigate the social network.

Pedestrian Experiments

Physical Review E - In human crowds, interactions among individuals give rise to a variety of self-organized collective motions that help the group to effectively solve the problem of coordination. However, it is still not known exactly how humans adjust their behavior locally, nor what are the direct consequences on the emergent organization. One of the underlying mechanisms of adjusting individual motions is the stepping dynamics. In this paper, we present first quantitative analysis on the stepping behavior in a one-dimensional pedestrian flow studied under controlled laboratory conditions.We find that the step length is proportional to the velocity of the pedestrian, and is directly related to the space available in front of him, while the variations of the step duration are much smaller. This is in contrast with locomotion studies performed on isolated pedestrians and shows that the local density has a direct influence on the stepping characteristics. Furthermore, we study the phenomena of synchronization—walking in lock step—and show its dependence on flow densities. We show that the synchronization of steps is particularly important at high densities, which has direct impact on the studies of optimizing pedestrians’ flow in congested situations. However, small synchronization and antisynchronization effects are found also at very low densities, showing the natural tendency to synchronize according to perceived visual signals.

Cellular Tug-of-War: Measuring the Forces as Cells Divide

LS13909 - New generations of cells are generated when existing cells divide: how do physical forces drive this process? In this Letter, we quantify for the first time the force exerted by dividing cells to their surroundings. We observed dividing Dictyostelium cells, a simple model organism for the study of cell division, and measured the force acting between cells and their substrate by Traction Force Microscopy. We found that two sister cells have two force spots for each and using these spots as anchoring points, they apply strong pulling force to their connecting bridge. The pulling force gets stronger until the last step of division and then suddenly drops when the middle structure breaks. This result indicates that dividing cells pull each other using two footholds to separate just like a tug-of-war between two people. This study revealing the unexpected role of forces on cell division highlights the power of physical approach to understand this biologically important phenomenon.

Two-footed nanowalker powered by light

LT13770 - Artificial nanowalkers are inspired by biomolecular counterparts from living cells, but remain far from comparable to the latter in design principles. The walkers reported to date mostly rely on chemical mechanisms to gain a direction; they all produce chemical wastes. This paper reports a light-powered DNA bipedal walker based on a design principle derived from cellular walkers. The walker has two identical feet and the track has equal binding sites; yet the walker gains a direction by pure physical mechanisms that autonomously amplify an intra-site asymmetry into a ratchet effect without producing any chemical waste. It has a distinct thermodynamic feature that it possesses the same equilibrium before and after operation, but generates a truly non-equilibrium distribution during operation. The demonstrated design principle exploits mechanical effects for symmetry breaking and direction rectification, hence is adaptable for use in other nanomachines. The walker is advantageous for certain applications, especially biomedical ones, as it is free of chemical wastes, remotely controlled by light, and requires a low-level irradiation within the safety limit of biological tissues.

Secure cloud quantum computation with light

LV13623 - A first-generation quantum computer must be implemented in the ``cloud" style, since only governments or huge industries will be able to possess  such a super-expensive and high-maintenance object. Can we guarantee the security of client's privacy  in such a cloud quantum computing? The protocol of blind quantum computation can solve that problem. It is a new secure quantum computing protocol where a client, who does not have enough quantum technology, can

delegate her quantum computation to a server, who has a fully-fledged quantum computer, in such a way that the server cannot learn anything about client's input, output, and program. This protocol was recently experimentally realized in an optical system by Zeillinger's group at Vienna. In this experiment, the discrete degrees of freedom (polarization) of photons was used.  In this paper, we have shown that such a blind quantum computation is also possible by using the continuous degrees of freedom of photons. Quantum computation by using such a continuous degrees of freedom is one of the most central research subjects in today's quantum optics, and in fact plenty of experiments have been done. Hence our result will push the blind quantum computation to a new domain, and will open a door to more practical secure cloud quantum computation.