news tagged with: quantum gravity en-us internet news portal provides the latest news on science including: Physics, Nanotechnology, Life Sciences, Space Science, Earth Science, Environment, Health and Medicine. Computer simulation supports a "holographic" theory describing a black hole A "holographic" theory, which was conjectured to describe accurately the dynamical phenomena occurring in a black hole, has been tested numerically by a research group composed of four researchers: Masanori Hanada, Ph.D., an associate professor at Kyoto University; Yoshifumi Hyakutake, Ph.D., an associate professor at Ibaraki University; Goro Ishiki, Ph.D., an assistant professor at Kyoto University; and Jun Nishimura, Ph.D., an associate professor at KEK. Physics Wed, 07 May 2014 13:37:11 EST news318688612 Mapping the road to quantum gravity The road uniting quantum field theory and general relativity – the two great theories of modern physics – has been impassable for 80 years. Could a tool from condensed matter physics finally help map the way? Physics Wed, 23 Apr 2014 16:58:54 EST news317491119 Liquid spacetime: A very slippery superfluid, that's what spacetime could be like What if spacetime were a kind of fluid? This is the question tackled by theoretical physicists working on quantum gravity by creating models attempting to reconcile gravity and quantum mechanics. Some of these models predict that spacetime at the Planck scale (10-33cm) is no longer continuous – as held by classical physics – but discrete in nature. Just like the solids or fluids we come into contact with every day, which can be seen as made up of atoms and molecules when observed at sufficient resolution. A structure of this kind generally implies, at very high energies, violations of Einstein's special relativity (a integral part of general relativity). Physics Wed, 23 Apr 2014 09:19:30 EST news317463557 Creation of entanglement simultaneously gives rise to a wormhole Quantum entanglement is one of the more bizarre theories to come out of the study of quantum mechanics—so strange, in fact, that Albert Einstein famously referred to it as "spooky action at a distance." Physics Thu, 05 Dec 2013 09:18:01 EST news305457464 Proton radius puzzle may be solved by quantum gravity ( —Officially, the radius of a proton is 0.88 ± 0.01 femtometers (fm, or 10-15 m). Researchers attained that value using two methods: first, by measuring the proton's energy levels using hydrogen spectroscopy, and second, by using electron scattering experiments, where an electron beam is shot at a proton and the way the electrons scatter is used to calculate the proton's size. Physics Tue, 26 Nov 2013 12:46:40 EST news304692381 Quantum steps towards the Big Bang ( —Present-day physics cannot describe what happened in the Big Bang. Quantum theory and the theory of relativity fail in this almost infinitely dense and hot primal state of the universe. Only an all-encompassing theory of quantum gravity which unifies these two fundamental pillars of physics could provide an insight into how the universe began. Scientists from the Max Planck Institute for Gravitational Physics (Albert Einstein Institute) in Golm/Potsdam and the Perimeter Institute in Canada have made an important discovery along this route. According to their theory, space consists of tiny "building blocks". Taking this as their starting point, the scientists arrive at one of the most fundamental equations of cosmology, the Friedmann equation, which describes the universe. This shows that quantum mechanics and the theory of relativity really can be unified. Physics Tue, 03 Sep 2013 07:00:01 EST news297409279 GR20/Amaldi10: Space-time is not the same for everyone Before the Big Bang, space-time as we know it did not exist. So how was it born? The process of creating normal space-time from an earlier state dominated by quantum gravity has been studied for years by theorists at the Faculty of Physics, University of Warsaw. Recent analyses suggest a surprising conclusion: not all elementary particles are subject to the same space-time. Physics Tue, 09 Jul 2013 10:34:03 EST news292584830 Theorists apply loop quantum gravity theory to black hole ( —Physicists Rodolfo Gambini and Jorge Pullin of University of the Republic in Montevideo, Uruguay, and Louisiana State University respectively, have applied the theory of Loop Quantum Gravity (LQG) to a simplified black hole. In so doing, as they describe in their paper published in the journal Physical Review Letters, they suggest that instead of a singularity existing at its center, there is a portal to another universe. Physics Fri, 31 May 2013 08:50:02 EST news289205854 Study finds semiclassical gravity counterintuitive, but on the horizon of testability ( —One of the more controversial theories of quantum gravity, which attempts to unify quantum mechanics and general relativity, is semiclassical gravity, which was proposed in the 1960s. As its name suggests, semiclassical gravity involves a combination of quantum and classical components. Specifically, matter obeys the rules of quantum mechanics while gravity and the spacetime structure obey classical laws. Many physicists think that integrating quantum and classical systems in this way creates physical contradictions and mathematical inconsistencies. However, in a new paper, physicists have closely analyzed exactly how classical gravity might affect the quantum properties of macroscopic objects, and found that the effects of semiclassical gravity may be experimentally detectable with state-of-the-art technology. Physics Wed, 08 May 2013 09:00:01 EST news287213873 Curves in spacetime violate Heisenberg's uncertainty principle (—If an object traveling through spacetime can loop back in time in a certain way, then its trajectory can allow a pair of its components to be measured with perfect accuracy, violating Heisenberg's uncertainty principle. This new finding involves a particular trajectory called an open timelike curve (OTC), which is a special case of a closed timelike curve (CTC), a theoretical concept that has previously provoked controversy because it raises the possibility of traveling backwards in time. Physics Tue, 19 Feb 2013 09:00:01 EST news280404720 Spacetime: A smoother brew than we knew Spacetime may be less like foamy quantum beer and more like smooth Einsteinian whiskey, according to research led by physicist Robert Nemiroff of Michigan Technological University being presented today at the 221st American Astronomical Society meeting in Long Beach, Calif. Astronomy & Space Wed, 09 Jan 2013 20:25:53 EST news276985447 Strict limit on CPT violation from gamma-ray bursts Kenji Toma (Osaka Univ.), Shinji Mukohyama (Kavli IPMU, Univ. of Tokyo), Daisuke Yonetoku (Kanazawa Univ.) and their colleagues have used the photon polarization in three distant gamma-ray bursts detected by Japanese spacecraft as evidence that the polarization did not rotate during its long journey. This lack of rotation puts the most stringent constraints yet on the violation of a fundamental symmetry. This work is going to be published and highlighted in Physical Review Letters. Physics Fri, 07 Dec 2012 13:30:03 EST news274108653 Accelerators can search for signs of Planck-scale gravity (—Although quantum theory can explain three of the four forces in nature, scientists currently rely on general relativity to explain the fourth force, gravity. However, no one is quite sure of how gravity works at very short distances, in particular the shortest distance of all: the Planck length, or 10-35 m. So far, the smallest distance accessible in experiments is about 10-19 m at the LHC. Physics Mon, 15 Oct 2012 09:30:01 EST news269510423 Quantum causal relations: A causes B causes A A deeply rooted concept in everyday life is causality; the idea that events in the present are caused by events in the past and, in turn, act as causes for what happens in the future. Physicists from the University of Vienna and the Universite Libre de Bruxelles have shown that in quantum mechanics it is possible to conceive situations in which a single event can be both, a cause and an effect of another one. Physics Tue, 02 Oct 2012 13:18:09 EST news268402670 Spacetime: A smoother brew than we knew (—Spacetime may be less like beer and more like sipping whisky. Astronomy & Space Thu, 23 Aug 2012 06:46:44 EST news264923189 Physicists search for new physics in primordial quantum fluctuations ( -- Inflation, the brief period that occurred less than a second after the Big Bang, is nearly as difficult to fathom as the Big Bang itself. Physicists calculate that inflation lasted for just a tiny fraction of a second, yet during this time the Universe grew in size by a factor of 1078. Also during this time, a very important thing occurred: fluctuations in the quantum vacuum appeared, which later resulted in the temperature fluctuations in the cosmic microwave background (CMB) that in turn produced large-scale structures such as galaxies. But in a new study, physicists now think that their understanding of the features of primordial quantum fluctuations &#8211; also called the inflationary power spectrum &#8211; may require a few small corrections due to currently unknown physics. These new corrections could allow scientists to search for experimental evidence to test a variety of quantum gravity theories, including string theory. Physics Mon, 26 Mar 2012 11:20:02 EST news251976548 Looking at quantum gravity in a mirror Einstein's theory of gravity and quantum physics are expected to merge at the Planck-scale of extremely high energies and on very short distances. At this scale, new phenomena could arise. However, the Planck-scale is so remote from current experimental capabilities that tests of quantum gravity are widely believed to be nearly impossible. Now an international collaboration between the groups of Caslav Brukner and Markus Aspelmeyer at the University of Vienna and Myungshik Kim at Imperial College London has proposed a new quantum experiment using Planck-mass mirrors. Such an experiment could test certain predictions made by quantum gravity proposals in the laboratory. The findings will be published this week in Nature Physics. Physics Sun, 18 Mar 2012 14:00:32 EST news251297445 In the early universe, rapid expansion or something very weird ( -- The widely-accepted theory of cosmic inflation states that our universe expanded rapidly in the moments after its birth, resulting in the immense expanse we see today. Physics Mon, 27 Feb 2012 08:58:33 EST news249555281 Physicists propose test for loop quantum gravity ( -- As a quantum theory of gravity, loop quantum gravity could potentially solve one of the biggest problems in physics: reconciling general relativity and quantum mechanics. But like all tentative theories of quantum gravity, loop quantum gravity has never been experimentally tested. Now in a new study, scientists have found that, when black holes evaporate, the radiation they emit could potentially reveal &#147;footprints&#148; of loop quantum gravity, distinct from the usual Hawking radiation that black holes are expected to emit. Physics Tue, 03 Jan 2012 09:38:04 EST news244805864 Physicists investigate fate of five-dimensional black strings ( -- While black holes in four-dimensional space-time are stable and can persist for a long time, their higher-dimensional analogues are usually unstable. One such theoretical analogue is a five-dimensional black string, which is unstable to perturbations and tends to decay into different forms. But like all unstable "black objects," it's difficult to determine what the end state of the perturbed system might be. Using a new computer code, physicists have been able to simulate the evolution of five-dimensional black strings well beyond earlier studies, leading them to predict that the strings eventually turn into five-dimensional black holes. Physics Fri, 10 Sep 2010 08:30:02 EST news203318795 Physicists develop model that pushes limits of quantum theory, relativity All of the matter in the universe -- everything we see, feel and smell -- has a certain predictable structure, thanks to the tiny electrons spinning around their atomic nuclei in a series of concentric shells or atomic levels. A fundamental tenet of this orderly structure is that no two electrons can occupy the same atomic level (quantum state) at the same time—a principle called the Pauli exclusion principle, which is based on Albert Einstein's theory of relativity and quantum theory. Physics Tue, 03 Aug 2010 13:21:42 EST news200060488 Einstein equations indicate possibility of black hole formation at the LHC ( -- One of the concerns that has been voiced about the Large Hadron Collider (LHC), is that it could result in the formation of black holes that could destroy the world. While most scientists dismiss claims that anything produced in the LHC would destroy the planet, there are some that think that black formation could be seen with LHC collisions of sufficiently high energy. This idea has gotten a further boost from recent efforts by Matthew Choptuik at the University of British Columbia in Vancouver, and Frans Pretorius, at Princeton University in New Jersey. Physics Tue, 06 Apr 2010 04:33:34 EST news189694649 Proposed Spacetime Structure Could Provide Hints for Quantum Gravity Theory ( -- Spacetime, which consists of three dimensions of space and one time dimension, is such a large, abstract concept that scientists have a very difficult time understanding and defining it. Moreover, different theories offer different, contradictory insights on spacetime’s structure. While general relativity describes spacetime as a continuous manifold, quantum field theories require spacetime to be made of discrete points. Unifying these two theories into one theory of quantum gravity is currently one of the biggest unsolved problems in physics. Physics Wed, 16 Dec 2009 16:34:34 EST news180203376 Rewriting general relativity? Putting a new model of quantum gravity under the microscope Does an exciting but controversial new model of quantum gravity reproduce Einstein's theory of general relativity? Scientists at Texas A&M University in the US explore this question in a paper appearing in Physical Review Letters and highlighted with a Viewpoint in the August 24th issue of Physics. Physics Mon, 24 Aug 2009 12:20:01 EST news170333445 Researchers propose new way to reproduce a black hole ( -- Despite their popularity in the science fiction genre, there is much to be learned about black holes, the mysterious regions in space once thought to be absent of light. In a paper published in the August 20 issue of Physical Review Letters Dartmouth researchers propose a new way of creating a reproduction black hole in the laboratory on a much-tinier scale than their celestial counterparts. Physics Fri, 21 Aug 2009 13:50:01 EST news170081334 Vanquishing infinity: Old methods lead to a new approach to finding a quantum theory of gravity Quantum mechanics and Einstein's theory of general relativity are both extremely accurate theories of how the universe works, but all attempts to combine the two into a unified theory have ended in failure. When physicists try to calculate the properties of a quantum theory of gravity, they find quantities that become infinite -- infinities that are so bad they can't be removed by mathematical gambits that work in other areas of physics. Physics Mon, 17 Aug 2009 13:18:47 EST news169733869 Spacetime May Have Fractal Properties on a Quantum Scale ( -- Usually, we think of spacetime as being four-dimensional, with three dimensions of space and one dimension of time. However, this Euclidean perspective is just one of many possible multi-dimensional varieties of spacetime. For instance, string theory predicts the existence of extra dimensions - six, seven, even 20 or more. As physicists often explain, it’s impossible to visualize these extra dimensions; they exist primarily to satisfy mathematical equations. Physics Wed, 25 Mar 2009 12:40:14 EST news157203574 Physicists are first to 'squeeze' light to quantum limit ( -- A team of University of Toronto physicists have demonstrated a new technique to squeeze light to the fundamental quantum limit, a finding that has potential applications for high-precision measurement, next-generation atomic clocks, novel quantum computing and our most fundamental understanding of the universe. Physics Fri, 02 Jan 2009 12:30:18 EST news150121818 Fuzziness on the road to physics' grand unification theory Leave it to hypothesized gravity to weigh down what physicists have thought for 30 years. If theoretical physicists, led by the University of Oregon's Stephen Hsu, are right, the idea that nature's forces merge under grand unification has grown fuzzy. Physics Mon, 06 Oct 2008 12:55:33 EST news142516533