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pacome delva

Condensation transition in networks and other complex systems - 4 views

nuweb.neu.edu/...Condensation.html

phy bio complex_networks

shared by pacome delva on 15 Jan 10 - Cached
  • pacome delva on 15 Jan 10
     
    I like this work... it mixes physics, networks and biology ! Anyone heard about her ? Here's an interesting paper found on this website: http://nuweb.neu.edu/gbianconi/condensation.pdf
  • ...3 more comments...
  • Francesco Biscani on 15 Jan 10
     
    Eh... Barabasi is really milking the golden cow :) It seems interesting, even if I don't remember enough from my statistical mechanics classes to truly understand it without a major effort. Maybe you could make a layman's science coffee about it?
  • pacome delva on 15 Jan 10
     
    yeah i could if there's enough interest...? do u know Barabasi ?
  • Francesco Biscani on 15 Jan 10
     
    He's quite well known for his work on scale-free networks: http://en.wikipedia.org/wiki/Albert-L%C3%A1szl%C3%B3_Barab%C3%A1si He's applying them for everything and the kitchen sink :) We have a Barabasi-Albert network topology implemented in PaGMO...
  • Dario Izzo on 16 Jan 10
     
    We worked on this with Luzi a few years back ... while the analogy is original and interesting it fails to capture the dynamics of a network, e.g. if a network has hubs that grow and shrink .... Luzi worked on an extended model to solve this issue, but, if I remember correctly, he got stuck in a computationally very hard problem .... We intended to develop and use the extended model to define relevant characteristic of the ESA network formed by mail exchanges.....
  • nikolas smyrlakis on 18 Jan 10
     
    ...but then the CMS YGT didn't really like the project
Alexander Wittig

MAIUS 1 - First Bose-Einstein condensate generated in space - 0 views

www.dlr.de/...year-all

shared by Alexander Wittig on 24 Jan 17 - No Cached
jcunha liked it
  • Alexander Wittig on 24 Jan 17
     
    For the first time, ultra-cold atoms interfere in space The MAIUS 1 experiment was launched on 23 January 2017 at 3:30 CET on board a sounding rocket from Esrange Space Center near Kiruna in northern Sweden. German scientists have, for the first time, succeeded in producing a Bose-Einstein condensate in space and using it for interferometry experiments.
jcunha

Synthetic Landau levels for photons - 1 views

www.nature.com/...nature17943.html

PHY quantum hall effect topology experiment photons

shared by jcunha on 09 Jun 16 - No Cached
  • jcunha on 09 Jun 16
     
    Very nice experiment on the verge of Condensed matter Physics! The presence of Landau levels is a necessary condition to obtain a Quantum Hall state. Quantum Hall states have first appeared in 2D electronic gases when applied a perpendicular magnetic field that induces a new topological state of the "electronic gas". This new topological state is believed to "protect" some parameters of the system, such as conductance making it possible to measure fundamental constants with very high precision even in imperfect experimental conditions. In this fundamental experiment, a synthetic magnetic field was created that acts in continuum photons, producing "an integer quantum Hall system in curved space, a long-standing challenge in condensed matter physics".
Marcus Maertens

Physicists create synthetic magnetic monopole predicted more than 80 years ago - 1 views

phys.org/...c-magnetic-monopole-years.html

PHY

shared by Marcus Maertens on 30 Jan 14 - No Cached
  • Marcus Maertens on 30 Jan 14
     
    Hall's team adopted an innovative approach to investigating Dirac's theory, creating and identifying synthetic magnetic monopoles in an artificial magnetic field generated by a Bose-Einstein condensate, an extremely cold atomic gas tens of billionths of a degree warmer than absolute zero.
Athanasia Nikolaou

Nature Paper: Rivers and streams release more CO2 than previously believed - 6 views

www.klimacampus.de/631+M59214efc590.html

climate emissions

shared by Athanasia Nikolaou on 25 Nov 13 - No Cached
LeopoldS liked it
  • Athanasia Nikolaou on 25 Nov 13
     
    Another underestimated source of CO2, are turbulent waters. "The stronger the turbulences at the water's surface, the more CO2 is released into the atmosphere. The combination of maps and data revealed that, while the CO2 emissions from lakes and reservoirs are lower than assumed, those from rivers and streams are three times as high as previously believed." Alltogether the emitted CO2 equates to roughly one-fifth of the emissions caused by humans. Yet more stuff to model...
  • ...10 more comments...
  • Dario Izzo on 26 Nov 13
     
    This could also be a mechanism to counter human CO2 emission ... the more we emit, the less turbulent rivers and stream, the less CO2 is emitted there ... makes sense?
  • johannessimon81 on 27 Nov 13
     
    I guess there is a natural equilibrium there. Once the climate warms up enough for all rivers and streams to evaporate they will not contribute CO2 anymore - which stops their contribution to global warming. So the problem is also the solution (as always).
  • Athanasia Nikolaou on 27 Nov 13
     
    "The source of inland water CO2 is still not known with certainty and new studies are needed to research the mechanisms controlling CO2 evasion globally." It is another source of CO2 this one, and the turbulence in the rivers is independent of our emissions in CO2 and just facilitates the process of releasing CO2 waters. Dario, if I understood correct you have in mind a finite quantity of CO2 that the atmosphere can accomodate, and to my knowledge this does not happen, so I cannot find a relevant feedback there. Johannes, H2O is a powerful greenhouse gas :-)
  • Dario Izzo on 27 Nov 13
     
    Nasia I think you did not get my point (a joke, really, that Johannes continued) .... by emitting more CO2 we warm up the planet thus drying up rivers and lakes which will, in turn emit less CO2 :) No finite quantity of CO2 in the atmosphere is needed to close this loop ... ... as for the H2O it could just go into non turbulent waters rather than staying into the atmosphere ...
  • Athanasia Nikolaou on 03 Dec 13
     
    Really awkward joke explanation: I got the joke of Johannes, but maybe you did not get mine: by warming up the planet to get rid of the rivers and their problems, the water of the rivers will be accomodated in the atmosphere, therefore, the greenhouse gas of water.
  • Dario Izzo on 03 Dec 13
     
    from my previous post: "... as for the H2O it could just go into non turbulent waters rather than staying into the atmosphere ..."
  • johannessimon81 on 03 Dec 13
     
    I guess the emphasis is on "could"... ;-) Also, everybody knows that rain is cold - so more water in the atmosphere makes the climate colder.
  • LeopoldS on 03 Dec 13
     
    do you have the nature paper also? looks like very nice, meticulous typically german research lasting over 10 years with painstakingly many researchers from all over the world involved .... and while important the total is still only 20% of human emissions ... so a variation in it does not seem to change the overall picture
  • Athanasia Nikolaou on 04 Dec 13
     
    here is the nature paper : http://www.nature.com/nature/journal/v503/n7476/full/nature12760.html I appreciate Johannes' and Dario's jokes, since climate is the common ground that all of us can have an opinion, taking honours from experiencing weather. But, the same as if I am trying to make jokes for material science, or A.I. I take a high risk of failing(!) :-S Water is a greenhouse gas, rain rather releases latent heat to the environment in order to be formed, Johannes, nice trolling effort ;-) Between this and the next jokes to come, I would stop to take a look here, provided you have 10 minutes: how/where rain forms http://www.scribd.com/doc/58033704/Tephigrams-for-Dummies
  • Dario Izzo on 04 Dec 13
     
    omg
  • johannessimon81 on 09 Dec 13
     
    Nasia, I thought about your statement carefully - and I cannot agree with you. Water is not a greenhouse gas. It is instead a liquid. Also, I can't believe you keep feeding the troll! :-P But on a more topical note: I think it is an over-simplification to call water a greenhouse gas - water is one of the most important mechanisms in the way Earth handles heat input from the sun. The latent heat that you mention actually cools Earth: solar energy that would otherwise heat Earth's surface is ABSORBED as latent heat by water which consequently evaporates - the same water condenses into rain drops at high altitudes and releases this stored heat. In effect the water cycle is a mechanism of heat transport from low altitude to high altitude where the chance of infrared radiation escaping into space is much higher due to the much thinner layer of atmosphere above (including the smaller abundance of greenhouse gasses). Also, as I know you are well aware, the cloud cover that results from water condensation in the troposphere dramatically increases albedo which has a cooling effect on climate. Furthermore the heat capacity of wet air ("humid heat") is much larger than that of dry air - so any advective heat transfer due to air currents is more efficient in wet air - transporting heat from warm areas to a natural heat sink e.g. polar regions. Of course there are also climate heating effects of water like the absorption of IR radiation. But I stand by my statement (as defended in the above) that rain cools the atmosphere. Oh and also some nice reading material on the complexities related to climate feedback due to sea surface temperature: http://journals.ametsoc.org/doi/abs/10.1175/1520-0442(1993)006%3C2049%3ALSEOTR%3E2.0.CO%3B2
  • Athanasia Nikolaou on 10 Dec 13
     
    I enjoy trolling conversations when there is a gain for both sides at the end :-) . I had to check upon some of the facts in order to explain my self properly. The IPCC report states the greenhouse gases here, and water vapour is included: http://www.ipcc.ch/publications_and_data/ar4/wg1/en/faq-2-1.html Honestly, I read only the abstract of the article you posted, which is a very interesting hypothesis on the mechanism of regulating sea surface temperature, but it is very localized to the tropics (vivid convection, storms) a region of which I have very little expertise, and is difficult to study because it has non-hydrostatic dynamics. The only thing I can comment there is that the authors define constant relative humidity for the bottom layer, supplied by the oceanic surface, which limits the implementation of the concept on other earth regions. Also, we may confuse during the conversation the greenhouse gas with the Radiative Forcing of each greenhouse gas: I see your point of the latent heat trapped in the water vapour, and I agree, but the effect of the water is that it traps even as latent heat an amount of LR that would otherwise escape back to space. That is the greenhouse gas identity and an image to see the absorption bands in the atmosphere and how important the water is, without vain authority-based arguments that miss the explanation in the end: http://www.google.nl/imgres?imgurl=http://www.solarchords.com/uploaded/82/87-33833-450015_44absorbspec.gif&imgrefurl=http://www.solarchords.com/agw-science/4/greenhouse--1-radiation/33784/&h=468&w=458&sz=28&tbnid=x2NtfKh5OPM7lM:&tbnh=98&tbnw=96&zoom=1&usg=__KldteWbV19nVPbbsC4jsOgzCK6E=&docid=cMRZ9f22jbtYPM&sa=X&ei=SwynUq2TMqiS0QXVq4C4Aw&ved=0CDkQ9QEwAw
jmlloren

Exotic matter : Insight : Nature - 5 views

www.nature.com/...index.html

nan phy

shared by jmlloren on 03 Aug 10 - Cached
LeopoldS liked it
  • jmlloren on 03 Aug 10
     
    Trends in materials and condensed matter. Check out the topological insulators. amazing field.
  • ...12 more comments...
  • Luzi Bergamin on 03 Aug 10
     
    Aparently very interesting, will it survive the short hype? Relevant work describing mirror charges of topological insulators and the classical boundary conditions were done by Ismo and Ari. But the two communities don't know each other and so they are never cited. Also a way to produce new things...
  • jmlloren on 04 Aug 10
     
    Thanks for noticing! Indeed, I had no idea that Ari (don't know Ismo) was involved in the field. Was it before Kane's proposal or more recently? What I mostly like is that semiconductors are good candidates for 3D TI, however I got lost in the quantum field jargon. Yesterday, I got a headache trying to follow the Majorana fermions, the merons, skyrnions, axions, and so on. Luzi, are all these things familiar to you?
  • Luzi Bergamin on 04 Aug 10
     
    Ismo Lindell described in the early 90's the mirror charge of what is now called topological insulator. He says that similar results were obtained already at the beginning of the 20th century... Ismo Lindell and Ari Sihvola in the recent years discussed engineering aspects of PEMCs (perfect electro-megnetic conductors,) which are more or less classical analogues of topological insulators. Fundamental aspects of PEMCs are well knwon in high-energy physics for a long time, recent works are mainly due to Friedrich Hehl and Yuri Obukhov. All these works are purely classical, so there is no charge quantisation, no considerations of electron spin etc. About Majorana fermions: yes, I spent several years of research on that topic. Axions: a topological state, of course, trivial :-) Also merons and skyrnions are topological states, but I'm less familiar with them.
  • LeopoldS on 04 Aug 10
     
    "Non-Abelian systems1, 2 contain composite particles that are neither fermions nor bosons and have a quantum statistics that is far richer than that offered by the fermion-boson dichotomy. The presence of such quasiparticles manifests itself in two remarkable ways. First, it leads to a degeneracy of the ground state that is not based on simple symmetry considerations and is robust against perturbations and interactions with the environment. Second, an interchange of two quasiparticles does not merely multiply the wavefunction by a sign, as is the case for fermions and bosons. Rather, it takes the system from one ground state to another. If a series of interchanges is made, the final state of the system will depend on the order in which these interchanges are being carried out, in sharp contrast to what happens when similar operations are performed on identical fermions or bosons." wow, this paper by Stern reads really weired ... any of you ever looked into this?
  • jmlloren on 04 Aug 10
     
    C'mon Leopold, it's as trivial as the topological states, AKA axions! Regarding the question, not me!
  • LeopoldS on 04 Aug 10
     
    just looked up the wikipedia entry on axions .... at least they have some creativity in names giving: "In supersymmetric theories the axion has both a scalar and a fermionic superpartner. The fermionic superpartner of the axion is called the axino, the scalar superpartner is called the saxion. In some models, the saxion is the dilaton. They are all bundled up in a chiral superfield. The axino has been predicted to be the lightest supersymmetric particle in such a model.[24] In part due to this property, it is considered a candidate for the composition of dark matter.[25]"
  • jmlloren on 04 Aug 10
     
    Thank's Leopold. Sorry Luzi for being ironic concerning the triviality of the axions. Now, Leo confirmed me that indeed is a trivial matter. I have problems with models where EVERYTHING is involved.
  • Luzi Bergamin on 04 Aug 10
     
    Well, that's the theory of everything, isn't it?? Seriously: I don't think that theoretically there is a lot of new stuff here. Topological aspects of (non-Abelian) theories became extremely popular in the context of string theory. The reason is very simple: topological theories are much simpler than "normal" and since string theory anyway is far too complicated to be solved, people just consider purely topological theories, then claiming that this has something to do with the real world, which of course is plainly wrong. So what I think is new about these topological insulators are the claims that one can actually fabricate a material which more or less accurately mimics a topological theory and that these materials are of practical use. Still, they are a little bit the poor man's version of the topological theories fundamental physicists like to look at since electrdynamics is an Abelian theory.
  • jmlloren on 04 Aug 10
     
    I have the feeling, not the knowledge, that you are right. However, I think that the implications of this light quantum field effects are great. The fact of being able to sustain two currents polarized in spin is a technological breakthrough.
  • LeopoldS on 04 Aug 10
     
    not sure how much I can contribute to your apparently educated debate here but if I remember well from my work for the master, these non-Abelian theories were all but "simple" as Luzi puts it ... and from a different perspective: to me the whole thing of being able to describe such non-Abelian systems nicely indicates that they should in one way or another also have some appearance in Nature (would be very surprised if not) - though this is of course no argument that makes string theory any better or closer to what Luzi called reality ....
  • Luzi Bergamin on 04 Aug 10
     
    Well, electrodynamics remains an Abelian theory. From the theoretical point of view this is less interesting than non-Abelian ones, since in 4D the fibre bundle of a U(1) theory is trivial (great buzz words, eh!) But in topological insulators the point of view is slightly different since one always has the insulator (topological theory), its surrounding (propagating theory) and most importantly the interface between the two. This is a new situation that people from field and string theory were not really interested in.
  • Dario Izzo on 04 Aug 10
     
    guys... how would you explain this to your gran mothers?
  • jmlloren on 05 Aug 10
  • LeopoldS on 07 Aug 10
     
    *you* tried *your* best .... ??
Dario Izzo

Climatologists are no Einsteins, says his successor | NJ.com - 2 views

blog.nj.com/...tologists_are_no_einstein.html

climate

shared by Dario Izzo on 08 Apr 13 - No Cached
  • Dario Izzo on 08 Apr 13
     
    I know at least of a few people who share this point of view :)
  • johannessimon81 on 09 Apr 13
     
    I think it is worth noting that Dyson's is not saying that climate change is an illusion - it is evident that a lot of CO2 is emitted into the atmosphere and hence something will change. His point is that we just don't know what will change and by how much and that (much) more experimental data is necessary to make predictive models.
  • johannessimon81 on 11 May 13
     
    On missing experimental work: just read in the news that condensation in cirrus clouds has been studied recently and that the models where incorrect as to what the significance of organic substances and soot is in cirrus cloud formation. http://www.sciencemag.org/content/early/2013/05/08/science.1234145
aborgg

Carbon-rich nanorods harvest water from the air - 0 views

www.nature.com/...534298d.html

Nanoscience Fluid dynamics technology chemistry

shared by aborgg on 20 Jun 16 - No Cached
  • aborgg on 20 Jun 16
     
    Nanometre-sized rods of carbon can expel water in puffs of vapour when the air is already humid. Materials such as carbon and silica gels typically pick up moisture as humidity increases. But Satish Nune and his colleagues at the Pacific Northwest National Laboratory in Richland, Washington, found that their carbon-based nanorods take up water at low humidity and then give off about half of it when the relative humidity exceeds 50-80%. The team thinks that water condenses between adjacent rods and then capillary forces draw the rods together until the water bursts from the ends of the rods and evaporates.
pacome delva

Bosons bossed into Bose-Einstein condensate - physicsworld.com - 2 views

physicsworld.com/...44412

phy BEC photonics

shared by pacome delva on 26 Nov 10 - No Cached
  • LeopoldS on 27 Nov 10
     
    I am so proud to have posted this days before Pacome has spotted it :-)
Juxi Leitner

Technology Review: Blogs: arXiv blog: Physicist Discovers How to Teleport Energy - 4 views

www.technologyreview.com/...24759

tech phy quantum entanglement nrg

shared by Juxi Leitner on 09 Feb 10 - Cached
pacome delva liked it
  • He gives the example of a string of entangled ions oscillating back and forth in an electric field trap, a bit like Newton's balls. Measuring the state of the first ion injects energy into the system in the form of a phonon, a quantum of oscillation. Hotta says that performing the right kind of measurement on the last ion extracts this energy. Since this can be done at the speed of light (in principle), the phonon doesn't travel across the intermediate ions so there is no heating of these ions. The energy has been transmitted without traveling across the intervening space.
  • Juxi Leitner on 09 Feb 10
     
    wonder if we can use that to power a moon base .... or on-board a SBSP satellite
  • ...1 more comment...
  • LeopoldS on 09 Feb 10
     
    will still have to read the actual article but am a bit sceptic if this interpretation really will hold ... what are our fundamental physicists saying about this?
  • Juxi Leitner on 10 Feb 10
     
    I am not the physicist but I thought it might be interesting, from a space security point-of-view
  • pacome delva on 11 Feb 10
     
    Yes it seems really interesting and opens new possibilities. However this technology review article is not very good and the guy uses terms which have a precise meaning (like teleportation), which is different from the word we know... Quantum teleportation is what we use for designing quantum computers, but we are quite far from any practical applications. This energy teleportation will allow new scheme involving energy (if it is experimentally confirmed) which is very nice. However it seems this occurs in an entangled many-body system, which the only macroscopic one I know is a bose-eintein condensate (BEC). So it would mean infuse energy in the BEC by doing a measurement on one of the atom and extract it few millimeters away by doing a measurement on another atom. very far from any long distance power transmission...
Paul N

Bacteria Living in 'Cloud Cities' May Control Rain and Snow Patterns : DNews - 1 views

news.discovery.com/...nd-snow-an-unlikely-couple.htm

BIO science

shared by Paul N on 23 Aug 14 - No Cached
  • Paul N on 23 Aug 14
     
    Some bacteria can influence the weather. Up high in the sky where clouds form, water droplets condense and ice crystal grow around tiny particles. Typically these particles are dust, pollen, or even soot from a wildfire. But recently scientists have begun to realize that some of these little particles are alive - they are bacteria evolved to create ice or water droplets around themselves. old but might be worth a discussion
jaihobah

Black Hole Power: How String Theory Idea Could Lead to New Thermal-Energy Harvesting Te... - 0 views

spectrum.ieee.org/...thermal-energy-harvesting-tech

PHY NAN

shared by jaihobah on 21 Jul 17 - No Cached
LeopoldS liked it
  • jaihobah on 21 Jul 17
     
    A new class of exotic materials could find its way into next-generation technologies that efficiently convert waste heat into electrical current according to new research. Both the exotic materials and the means by which they generate electricity rely on a hybrid of advanced concepts-including string theory combined with black holes combined with cutting-edge condensed matter physics.
  • LeopoldS on 22 Jul 17
     
    Sounds spooky
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