Skip to main content

Home/ Advanced Concepts Team/ Group items tagged fundamental

Rss Feed Group items tagged

LeopoldS

An optical lattice clock with accuracy and stability at the 10-18 level : Nature : Natu... - 0 views

  •  
    Progress in atomic, optical and quantum science1, 2 has led to rapid improvements in atomic clocks. At the same time, atomic clock research has helped to advance the frontiers of science, affecting both fundamental and applied research. The ability to control quantum states of individual atoms and photons is central to quantum information science and precision measurement, and optical clocks based on single ions have achieved the lowest systematic uncertainty of any frequency standard3, 4, 5. Although many-atom lattice clocks have shown advantages in measurement precision over trapped-ion clocks6, 7, their accuracy has remained 16 times worse8, 9, 10. Here we demonstrate a many-atom system that achieves an accuracy of 6.4 × 10−18, which is not only better than a single-ion-based clock, but also reduces the required measurement time by two orders of magnitude. By systematically evaluating all known sources of uncertainty, including in situ monitoring of the blackbody radiation environment, we improve the accuracy of optical lattice clocks by a factor of 22. This single clock has simultaneously achieved the best known performance in the key characteristics necessary for consideration as a primary standard-stability and accuracy. More stable and accurate atomic clocks will benefit a wide range of fields, such as the realization and distribution of SI units11, the search for time variation of fundamental constants12, clock-based geodesy13 and other precision tests of the fundamental laws of nature. This work also connects to the development of quantum sensors and many-body quantum state engineering14 (such as spin squeezing) to advance measurement precision beyond the standard quantum limit.
Francesco Biscani

The End Of Gravity As a Fundamental Force - 6 views

  •  
    "At a symposium at the Dutch Spinoza-instituut on 8 December, 2009, string theorist Erik Verlinde introduced a theory that derives Newton's classical mechanics. In his theory, gravity exists because of a difference in concentration of information in the empty space between two masses and its surroundings. He does not consider gravity as fundamental, but as an emergent phenomenon that arises from a deeper microscropic reality. A relativistic extension of his argument leads directly to Einstein's equations."
  • ...8 more comments...
  •  
    Diffcult for me to fully understand / believe in the holographic principle at macroscopical scales ... potentially it looks though as a revolutionary idea.....
  •  
    never heard about it... seems interesting. At first sight it seems that it is based on fundamental principle that could lead to a new phenomenology, so that could be tested. Perhaps Luzi knows more about this ? Did we ever work on this concept ?
  •  
    The paper is quite long and I don't have the time right now to read it in detail. Just a few comments: * We (ACT) definitely never did anything in this direction? But: is there a new phenomenology? I'm not sure, if the aim is just to get Einstein's theory as emergent theory, then GR should not change (or only change in extreme conditions.) * Emergent gravity is not new, also Erik admits that. The claim to have found a solution appears quite frequently, but most proposals actually are not emergent at all. At least, I have the impression that Erik is aware of the relevant steps to be performed. * It's very difficult to judge from a short glance at the paper, up to which point the claims are serious and where it just starts to be advertisments. Section 6 is pretty much a collection of self-praise. * Most importantly: I don't understand how exactly space and time should be emergent. I think it's not new to observe that space is related to special canonical variables in thermodynamics. If anybody can see anything "emergent" in the first paragraphs of section 3, then please explain me. For me, this is not emergent space, but space introduced with a "sledge hammer." Time anyway seems to be a precondition, else there is nothing like energy and nothing like dynamics. * Finally, holography appears to be a precondition, to my knowledge no proof exists that normal (non-supersymmetric, non-stringy, non-whatever) GR has a holographic dual.
  •  
    Update: meanwhile I understood roughly what this should be about. It's well known that BH physics follow the laws of theormodynamics, suggesting the existence of underlying microstates. But if this is true, shouldn't the gravitational force then be emergent from these microstates in the same way as any theromdynamical effect is emergent from the behavior of its constituents (e.g. a gas)? If this can be prooven, then indeed gravity is emergent. Problem: one has to proof that *any* configuration in GR may be interpreted as thermodynamical, not just BHs. That's probably where holography comes into the play. To me this smells pretty much like N=4 SYM vs. QCD. The former is not QCD, but can be solved, so all stringy people study just that one and claim to learn something about QCD. Here, we look at holographic models, GR is not holographic, but who cares... Engineering problems...
  •  
    is there any experimental or observational evidence that points to this "solution"?
  •  
    Are you joking??? :D
  •  
    I was a bit fast to say it could be tested... apparently we don't even know a theory that is holographic, perhaps a string theory (see http://arxiv.org/abs/hep-th/9409089v2). So very far from any test...
  •  
    Luzi, I miss you!!!
  •  
    Leo, do you mean you liked my comment on your question more than Pacome's? Well, the ACT has to evolve and fledge, so no bullshitting anymore, but serious and calculating answers... :-) Sorry Pacome, nothing against you!! I just LOVE this Diigo because it gives me the opportunity for a happy revival of my ACT mood.
  •  
    haha, today would have been great to show your mood... we had a talk on the connection between mind and matter !!
jcunha

Synthetic Landau levels for photons - 1 views

  •  
    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".
jaihobah

The Network Behind the Cosmic Web - 1 views

shared by jaihobah on 18 Apr 16 - No Cached
  •  
    "The concept of the cosmic web-viewing the universe as a set of discrete galaxies held together by gravity-is deeply ingrained in cosmology. Yet, little is known about architecture of this network or its characteristics. Our research used data from 24,000 galaxies to construct multiple models of the cosmic web, offering complex blueprints for how galaxies fit together. These three interactive visualizations help us imagine the cosmic web, show us differences between the models, and give us insight into the fundamental structure of the universe."
jmlloren

Cool Tools - Systemantics - 1 views

shared by jmlloren on 26 Feb 14 - No Cached
dejanpetkow liked it
  •  
    We begin at the beginning, with the Fundamental Theorem: New systems mean new problems.
Ma Ru

Here come gravitational waves - 3 views

  •  
    Here you go. You can now scrap Lisa altogether. Who's going to tell Pacome?
  •  
    Awesome and exciting stuff indeed! The data pinpoint the time when inflation occurred - about 10E-37 seconds into the Universe's life - and its temperature at the time, corresponding to energies of about 10E16 gigaelectronvolts, says cosmologist Michael Turner of the University of Chicago. That is the same energy at which three of the four fundamental forces of nature - the weak, strong and electromagnetic force - are expected to become indistinguishable from one another in a model known as the grand unified theory. I expect more fundamental physics insights to come out of this in the future. A full-sky survey from space may still be an interesting addition to the measurement capabilities, so I would not rule out LISA all together I guess...
jmlloren

Exotic matter : Insight : Nature - 5 views

shared by jmlloren on 03 Aug 10 - Cached
LeopoldS liked it
  •  
    Trends in materials and condensed matter. Check out the topological insulators. amazing field.
  • ...12 more comments...
  •  
    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...
  •  
    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?
  •  
    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.
  •  
    "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?
  •  
    C'mon Leopold, it's as trivial as the topological states, AKA axions! Regarding the question, not me!
  •  
    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]"
  •  
    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.
  •  
    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.
  •  
    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.
  •  
    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 ....
  •  
    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.
  •  
    guys... how would you explain this to your gran mothers?
  •  
    *you* tried *your* best .... ??
Luís F. Simões

Bitcoin P2P Currency: The Most Dangerous Project We've Ever Seen - 10 views

  • After month of research and discovery, we’ve learned the following:1. Bitcoin is a technologically sound project.2. Bitcoin is unstoppable without end-user prosecution.3. Bitcoin is the most dangerous open-source project ever created.4. Bitcoin may be the most dangerous technological project since the internet itself.5. Bitcoin is a political statement by technotarians (technological libertarians).*6. Bitcoins will change the world unless governments ban them with harsh penalties.
  • The benefits of a currency like this:a) Your coins can’t be frozen (like a Paypal account can be)b) Your coins can’t be trackedc) Your coins can’t be taxedd) Transaction costs are extremely low (sorry credit card companies)
  • An individual with the name -- or perhaps handle -- of Satoshi Nakamoto first wrote about bitcoins in a paper called Bitcoin: A Peer-to-Peer Electronic Cash System.
  • ...1 more annotation...
  • * We made this term up to describe the “good people” of the internet who believe in the fundamental rights of individuals to be free, have free speech, fight hypocrisy and stand behind logic, technology and science over religion, political structure and tradition. These are the people who build and support things like Wikileaks, Anonymous, Linux and Wikipedia. They think that people can, and should, govern themselves. They are against external forms of control such as DRM, laws that are bought and sold by lobbyists, and religions like Scientology. They include splinter groups that enforce these ideals in the form of hacktivism, such as the takedown of the Sony Playstation Network after Sony tried to prosecute a hacker for unlocking its console.
  •  
    Sounds good!
  • ...9 more comments...
  •  
    wow it's frigthening! it's the dream of every anarchist, every drug, arm, human dealer! the world made as a global fiscal paradise... the idea is clever however it will not replace real money because 1 - no one will build a fortune on bitcoin if a technological breakthrough can ruin them 2 - government never allowed parallel money to flourish on their territory, so it will be almost impossible to change bitcoin against euros or dollars
  •  
    interesting stuff anyone read cryptonomicon by neal stephenson? similar theme.
  •  
    :) yes. One of the comments on reddit was precisely drawing the parallels with Neal Stephenson's Snowcrash / Diamond Age / Cryptonomicon. Interesting stuff indeed. It has a lot of potential for misuse, but also opens up new possibilities. We've discussed recently how emerging technologies will drive social change. Whether it's the likes of NSA / CIA who will benefit the most from the Twitters, Facebooks and so on, by gaining greater power for control, or whether individuals are being empowered to at least an identical degree. We saw last year VISA / PayPal censoring WikiLeaks... Well, here's a way for any individual to support such an organization, in a fully anonymous and uncontrollable way...
  •  
    One of my colleagues has made a nice, short write-up about BitCoin: http://www.pds.ewi.tudelft.nl/~victor/bitcoin.html
  •  
    very nice analysis indeed - thanks Tamas for sharing it!
  •  
    mmm I'm not an expert but it seemed to me that, even if these criticisms are true, there is one fundamental difference between the money you exchange on internet via your bank, and bitcoins. The first one is virtual money and the second one aims at being real, physical, money, even if digital, in the same way as banknotes, coins, or gold.
  •  
    An algorithm wanna-be central bank issuing untraceable tax free money between internet users? not more likely than the end of the world supposed to take place tomorrow, in my opinion. Algorithms don't usually assault women though !:P
  •  
    well, most money is anyway just virtual and only based on expectations and trust ... (see e.g. http://en.wikipedia.org/wiki/Money_supply) and thus if people trust that this "money" has some value in the sense that they can get something of value to them in exchange, then not much more is needed it seems to me ...
  •  
    @Leopold: ok let's use the rigth words then. Bitcoin aim at being a currency ("physical objects generally accepted as a medium of exchange" from wikipedia), different than the "demand deposit". In the article proposed by Tamas he compares what cannot be compared (currencies, demand deposits and their mean of exchange). The interesting question is wether one can create a digital currency which is too difficult to counterfeit. As far as I know, there is no existing digital currency except this bitcoins (and maybe the currencies from games as second life and others, but which are of limited use in real world).
  •  
    well of course money is trust, and even more loans and credit and even more stock and bond markets. It all represents trust and expectations. However since the first banks 500 years ago and the first loans etc. etc., and as well the fact that bonds and currencies bring down whole countries (Greece lately), and are mainly controlled by large financial centres and (central) banks, banks have always been on the winning side no matter what and that isn't going to change easily. So if you are talking about these new currencies it would be a new era, not just a new currency. So should Greece convert its debt to bitcoins ;P ?
  •  
    well, from 1936 to 1993 the central bank of france was owned by the state and was supposed to serve the general interest...
jmlloren

Experimental verification of the feasibility of a quantum channel between space and Earth - 0 views

  •  
    Extending quantum communication to space environments would enable us to perform fundamental experiments on quantum physics as well as applications of quantum information at planetary and interplanetary scales. Here, we report on the first experimental study of the conditions for the implementation of the single-photon exchange between a satellite and an Earth-based station. We built an experiment that mimics a single photon source on a satellite, exploiting the telescope at the Matera Laser Ranging Observatory of the Italian Space Agency to detect the transmitted photons. Weak laser pulses, emitted by the ground-based station, are directed toward a satellite equipped with cube-corner retroreflectors. These reflect a small portion of the pulse, with an average of less-than-one photon per pulse directed to our receiver, as required for faint-pulse quantum communication. We were able to detect returns from satellite Ajisai, a low-Earth orbit geodetic satellite, whose orbit has a perigee height of 1485 km.
  •  
    hello Jose! Interesting it was proposed to do the same with the ISS as part of the ACES experiment. I don't remember the paper but i can look if you're interested
ESA ACT

The secret energy store of enzymes revealed - fundamentals - 08 January 2008 - New Scie... - 0 views

  •  
    interesting for biomimetic ideas??
ESA ACT

c-jump: computer programming board game - 0 views

  •  
    Discover fundamentals of computer programming by playing a board game!
ESA ACT

Alife XI - 0 views

  •  
    Artificial life investigates the fundamental properties of living systems through simulating and synthesizing biological entities and processes in artificial media.
ESA ACT

MRS Issue on Negative-Index Materials - 0 views

  •  
    How light travels through a material is measured by the index of refraction, a fundamental optical constant long thought to be an intrinsic materials property. However, research has shown that features manipulated through nanofabrication techniques can le
nikolas smyrlakis

Bio-Mimetic Approaches in Management Science, Book - Barnes & Noble - 1 views

  •  
    Oh yes somebody seems to have found a link between CMS and Biomimetics. Everything is possible now, even Fundamental physics !
  •  
    Neural networks = biomimetics. That's the conclusion from the TOC. It seems that biomimetics becomes the worse usurper than string theory.
Isabelle Dicaire

Testing of a femtosecond pulse laser in outer space : Scientific Reports : Nature Publi... - 2 views

  •  
    Good news for fundamental physics and Earth system science, femtosecond lasers are now about to achieve space qualification thanks to fibre optics!  Applications include high resolution spectroscopy, absolute laser ranging, mapping of the geo-potential and testing of the theory of general relativity to name a few!
  •  
    nice paper by the Koreans, did not know that they had already such a laser in orbit for a year. How much would this type be upscalable for our needs? in case we have not, we should reference it
jaihobah

Evidence Found for a New Fundamental Particle - 4 views

  •  
    An experiment at the Fermi National Accelerator Laboratory near Chicago has detected far more electron neutrinos than predicted - a possible harbinger of a revolutionary new elementary particle called the sterile neutrino, though many physicists remain skeptical.
jaihobah

Fundamental physics is frustrating physicists - 3 views

  •  
    No GUTs, no glory
LeopoldS

Host-to-host airborne transmission as a multiphase flow problem for science-based socia... - 0 views

  •  
    addressing some of the fundamentals of particle flow in air ...
johannessimon81

ESA article on magnetic reconnection, related: solar flares, earth magnetic field jets,... - 0 views

  •  
    ESA Science & Technology: A leap forward in probing magnetic reconnection in space: Magnetic reconnection is a fundamental physical process in the Universe, playing a major role in various phenomena such as star formation or solar explosions, but also preventing plasma confinement in fusion reactors on Earth. However, a lack of precise measurements at the heart of this physical process prevents a full understanding of this phenomenon.
Alexander Wittig

Has a Hungarian physics lab found a fifth force of nature? - 1 views

  •  
    MTA-Atomki A laboratory experiment in Hungary has spotted an anomaly in radioactive decay that could be the signature of a previously unknown fifth fundamental force of nature, physicists say - if the finding holds up. Would be cool, after all the high energy physics being done to verify the SM it could be extended at the other end where nobody bothered to look ;)
1 - 20 of 52 Next › Last »
Showing 20 items per page