Dark matter supposedly makes up 85% of the matter in the universe, but so far, efforts to catch hypothesized dark matter particles have all ended in failure. Weakly interacting massive particles (WIMPs) are no-shows at grand experiments housed in Italy, Canada, and the United States. Even tinier axions have not been detected either. Neutralinos, born out of supersymmetry, may look nice on paper but so far have no bearing on reality.
The standard model of modern cosmology is unthinkable without dark matter, although direct detections are still missing. A broad perspective of how dark matter was postulated and became accepted is presented, from prehistory, over observations of galaxy clusters, galaxy rotation curves, the search for baryonic dark matter, possible alternative explanations via modified gravity, up to the hunt for dark matter particles. The interplay is described between observational discoveries and theoretical arguments which led finally to the adoption of this paradigm.
If you replace classical bits with qubits, though, you go back to only needing one per spin in the system, because all the quantum stuff comes along for free. You don&s;t need extra bits to track the superposition, because the qubits themselves can be in superposition states. And you don&s;t need extra bits to track the entanglement, because the qubits themselves can be entangled with other qubits. A not-too-big quantum computer— again, 50–100 qubits— can efficiently solve problems that are simply impossible for a classical computer.
These sorts of problems pop up in useful contexts, such as the study of magnetic materials, whose magnetic nature comes from adding together the quantum spins of lots of particles, or some types of superconductors. As a general matter, any time you&s;re trying to find the state of a large quantum system, the computational overhead needed to do it will be much less if you can map it onto a system of qubits than if you&s;re stuck using a classical computer.
So, there&s;s your view-from-30,000-feet look at what quantum computing is, and what it&s;s good for. A quantum computer is a device that exploits wave nature, superposition, and entanglement to do calculations involving collective mathematical properties or the simulation of quantum systems more efficiently than you can do with any classical computer. That&s;s why these are interesting systems to study, and why heavy hitters like Google, Microsoft, and IBM are starting to invest heavily in the field.
The Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN) near Geneva, Switzerland is said to be the largest particle accelerator in the world. The accelerator occupies a tunnel 27 kilometers in circumference as deep as 175 meters beneath the French-Swiss border. The facility has helped scientists uncover the Higgs boson, the last particle predicted by the Standard Model, in 2012.
The particle physicists at the Niels Bohr Institute have obtained new results, working with the LHC, replacing the lead-ions, usually used for collisions, with Xenon-ions. Xenon is a “smaller” atom with fewer nucleons in its nucleus. When colliding ions, the scientists create a fireball that recreates the initial conditions of the universe at temperatures in excess of several thousand billion degrees. In contrast to the Universe, the lifetime of the droplets of QGP produced in the laboratory is ultra short, a fraction of a second (In technical terms, only about 10-22 seconds). Under these conditions the density of quarks and gluons is very large and a special state of matter is formed in which quarks and gluons are quasi-free (dubbed the strongly interacting QGP). The experiments reveal that the primordial matter, the instant before atoms formed, behaves like a liquid that can be described in terms of hydrodynamics.
How to approach “the moment of creation”
“One of the challenges we are facing is that, in heavy ion collisions, only the information of the final state of the many particles which are detected by the experiments are directly available – but we want to know what happened in the beginning of the collision and first few moments afterwards”, You Zhou, Postdoc in the research group Experimental Subatomic Physics at the Niels Bohr Institute, explains. “We have developed new and powerful tools to investigate the properties of the small droplet of QGP (early universe) that we create in the experiments”. They rely on studying the spatial distribution of the many thousands of particles that emerge from the collisions when the quarks and gluons have been trapped into the particles that the Universe consists of today. This reflects not only the initial geometry of the collision, but is sensitive to the properties of the QGP. It can be viewed as a hydrodynamical flow.
A peroxide scavenger nanoparticle reduces systemic inflammation in mouse models.
With 19 million cases per year worldwide, sepsis is one of the most life-threatening conditions in the intensive care unit. However, to date, there is no specific and effective treatment. Oxidative stress has been shown to play a major role in sepsis pathogenesis by altering the systemic immune response to infections, which, in turn, may lead to multiorgan dysfunction and cognitive impairment. Here, Rajendrakumar et al. developed a nanoparticle-based peroxide scavenger treatment for reducing oxidative stress during sepsis.
To produce the nanoassembly, the authors first developed a water-soluble nanoparticle core containing an active peroxide scavenger and a protein that stabilizes the scavenger and improves its biocompatibility. The nanoparticle core was then coated with a polymer material conjugated with mannose to help the final nanoassembly target inflammatory immune cells through the mannose receptor on the immune cell surfaces. The authors first confirmed in cell cultures that the nanoassembly can selectively reduce hydrogen peroxide–mediated free radical production with minimal toxicity. In cultures, immune cells demonstrated enhanced intracellular uptake of the particles and reduced production of inflammatory markers during activation. To demonstrate the therapeutic efficacy in vivo, the authors carried out three sets of animal studies. In the first set, the nanoassembly was shown to reduce locally induced tissue inflammation and prevent inflammatory immune cell infiltration.
For the first time, physicists have built a unique topological insulator in which optical and electronic excitations hybridize and flow together. They report their discovery in Nature.
Topological insulators are materials with very special properties. They conduct electricity or light particles only on their surface or edges, not the interior. This unusual characteristic could provide technical innovations, and topological insulators have been the subject of intense global research for several years.
Physicists of Julius-Maximilians-Universität Würzburg (JMU) in Bavaria, Germany, with colleagues from the Technion in Haifa, Israel, and Nanyang Technological University in Singapore have reported their discovery in the journal Nature. The team has built the first “exciton-polariton topological insulator,” a topological insulator operating with both light and electronic excitations simultaneously.
