A talk by P A Lee on SC and FM coexisting in oxide interface

http://videochannel.ust.hk/Watch.aspx?Section=Channels&Channel=2&SubType=All&View=Icon&Sort=Date&Page=1&Current=3&Mode=Play

A video on A.Einstein

http://www.youtube.com/watch?v=RVJyaJ5TNpc

http://www.youtube.com/watch?v=uKrRocH8M5M&feature=fvwrel

http://www.youtube.com/watch?v=i6XWNUzEZkY&feature=related

http://www.youtube.com/watch?v=mHM0SYyGfcw&feature=related

http://www.youtube.com/watch?v=dB6_0pcUfBc&feature=related

http://www.youtube.com/watch?v=Dtk_gChLchw&feature=related

ACCP

This website collects plenty of information of American scientists who have been working in US since 1945 to present. http://www.aip.org/history/acap/

Why bother to go that way ? No need at all

When an institution or a college recruits a researcher, she expects the researcher to lay eggs and to lay gold eggs. But even the researcher himself cannot be sure that he is bound to lay gold eggs. Not only that, what appears more confusing is about the definition of 'gold'. What appears 'gold' to the researcher may not appear so to other researchers and to the employer. In many cases, the employer seeks superficial 'goldness' (such as the impact factor of the journal the papers are published), knowing nothing about the content (such as what is the work discussed in that paper and how it adds value to the body of knowledge) that is inside. A researcher must be tough enough to withstand such pressure, which is really vicious and irrational. A good and confident researcher knows and has to know how to handle such situations. In my opinion, one just needs assure that his work is of good quality (at least satisfying himself who is supposed to be ultimately honest) and then writes it up in a nice paper and submit it to a widely known and read journal for publication. No need to wrestle too much with editor procedures. No need to squeeze yourself into a narrow journal that is inappropriately crowded. No need to seek that outward reputation. If your work is gold, it will glow and will be appreciated eventually.

Back now

You know, on the world there are some undercivilized areas, where no connections to certain websites are possible due to something called the 'great fire wall'. I had been in one of such shit areas days. And this misfortune will go on in the coming six months. I need to commute between where I am and that culturally barren area.

Cohen in a lecture

He gave a lecture on his recent work, in which he has listed a handful of his work on graphene, on photovoltaics, nano structures and superconductors. It might be worthy to put the link here: http://videochannel.ust.hk/Watch.aspx?Section=Channels&Channel=2&SubType=All&View=Icon&Sort=Date&Page=3&Current=30&Mode=Play

Inaugural Article By C M Will

I really like the nice article by physicist Will. It is titled "On the unreasonable effectiveness of the post-newtonian approximation in gravitational physics". I think, it is accessible to anyone with a fundamental knowledge of general relativity (GR). Personally, I suddenly feel the study of GR so handy. Before I read this article, GR to me is quite like an abstract. This article shows me the experimental aspects in light of GR equations. OK. read it for yourself. [PNAS, 108:5938(2011)].

Q&A with Philip Philips

You cannot fail to recognize him ! He has a good head of hairs ! [10.1126/science.caredit.a1100031]

Phillips, whose Ph.D. is in theoretical chemistry, says he probably would not have taken such an unusual approach if his background had been more conventional. Science Careers talks to Phillips about how his circuitous route from chemistry to physics prepared him to go down this new research avenue.

The following highlights from the interview were edited for brevity and clarity.

Q: How did you first become interested in science?

P.P.: My parents were in the humanities. I was born in Tobago, and we moved to the U.S. when I was 10. I was very interested in math as a kid. Science was interesting, but I had very bad teachers in high school and so I had no real way of knowing what science would be about.

At the university, I took a chemistry class, and that's when I really became interested in science. So I started taking many more science classes, and I realized too late that my real interest was in physics. I needed one more class for a physics major, and so I had degrees in math and chemistry.

Q: How did you go about choosing your Ph.D. program?

P.P.: I wanted to be a theoretician because math was always my thing, and if I was going to do science, I wanted to apply math to understanding physical problems. [But] I realized, given my limited undergraduate background, that somehow being able to chart a course that was intellectually what would be my focus for the rest of my life was just not possible. So I viewed a Ph.D. as a degree in which I learned how to do research, and the particular problem wasn't something I was deeply interested in at all. My project was on explaining phosphorescence lifetimes in small molecules.

Q: Did you get what you needed out of your Ph.D.?

P.P.: I had an adviser who was an incredibly brilliant person, and he really taught me how to get something done. He gave me this sense of just being able to take on a challenge even if you have no experience with the field.

Q: What was your next step?

P.P.: I got a Miller Fellowship at [the University of California,] Berkeley. The key thing I got interested in was disordered systems, and I started really thinking about many-body systems and phenomena that arise from collective physics, the sorts of things that would define my career.

I just started reading all the papers, and then I defined a new problem that others had not solved that I thought would advance the field. So the problem I was working on at Berkeley was an electron moving in a random array of scatterers. I learned the necessary math tricks to be able to solve this problem, and then I started doing it. That's what I'd learned from my adviser: how to chop something down that is completely new and make progress on it.

As a Miller fellow, I was doing this on my own. It was a big jump from single-particle stuff to, essentially, statistical mechanics, and the mindset was very different. It was painful and a lot of stuff I had to learn, but it was what I knew I wanted to do.

This Science Careers article is a tie-in to Science magazine’s feature on superconductivity.

Q: You then obtained a faculty position at the Massachusetts Institute of Technology (MIT), in the chemistry department. What did you work on there?

P.P.: This problem led me to look at Anderson localization, which is the problem of electrons moving in a random lattice. Solids have a regular array of atoms, and what Anderson showed is that if enough of the atoms are different, the electrons change from being able to move freely to being completely stuck. In one and two dimensions, it's generally been thought that any amount of disorder would lead to localization. But we found the general exceptions. And then I showed that certain classes of conducting polymers could be explained by the examples that lead to exceptions to localization. That application was motivated entirely because I was in a chemistry department.

Q: You then decided to move to Illinois after 9 years at MIT. Why?

P.P.: I was forced out. What I was doing had nothing to do with their definition of chemistry. Some supported me and some didn't. But even if I had gotten tenure, I would have had to move to a physics department.

Q: Were you aware at the time that you were risking tenure?

P.P.: Yes, I was very much aware of this. You have to be honest with yourself. There were no problems in chemistry that interested me. I have always just thought that you should do what you think is important regardless of whether it might work out or regardless of whether or not your colleagues think it will work out.

Q: You obtained tenure at the University of Illinois right away. Do you feel as though you've found your place now?

P.P.: Illinois has been absolutely a gold mine for me, yes. Personality-wise, in terms of the research I'm able to pursue here, in terms of a supportive environment, in terms of my research being central to the condensed matter effort of the department.

Credit: Rick Kubetz, University of Illinois

Philip Phillips collaborated with theoretical particle physicist Robert Leigh, also of the University of Illinois, Urbana-Champaign. Not shown in the picture and also contributors to the work are postdoctoral fellow Mohammad Edalati and graduate student Ka Wai Lo.

Q: So what has been your focus at Illinois?

P.P.: The big problem I have been trying to solve since 1995 is the physics of strongly coupled electron systems. I have been attempting to figure out what it is that the electrons are doing as they interact with one another [within cuprate superconductors]. Our work shows that they form composites, and so once you understand what the composites are, then you can begin to describe the macroscopic properties of the system.

[In 1998, Argentinean physicist Juan] Maldacena made a conjecture in which he argued that there is a relationship between a strongly coupled quantum mechanical system and a gravitational system [that] is entirely classical Einsteinian gravity. So in fact, strongly coupled quantum mechanical systems that are charged are equivalent to a curved space-time with a black hole in it. We showed that if you just introduce some probe fermions and these probe fermions are coupled to the space-time in a particular way, that system looks identical to the normal [nonsuperconducting] state of high-temperature superconductors.

Others have used this mapping before. What we did that was new is that we used a particular interaction between the probe fermions and the black hole that is really irrelevant to the physics of the black hole but changes the physics at the boundary of the space-time [which is where the quantum mechanical theory lives]. No one suspected it.

With such a model, you can just forget about trying to figure out what the basic building blocks are, just go and solve this geometry problem and extrapolate it to what's going on at the surface of this geometry, and you'll see what the quantum mechanical system is doing.

Q: And so have all these years of getting closer to your true scientific interests finally paid off?

P.P.: It takes a lot of daring to invest the time to go and learn this machinery [for geometrizing quantum mechanics] because it's fairly nontrivial stuff, and to think that it has answers for a real-life system is another risk.

I certainly thought that, God, if I were more traditionally trained, maybe I could have known some of the pitfalls of some of the things I've tried in the past. But now it's turning out that it was a good thing. The most important thing about my roundabout way is that I don't have any biases. I'm very open to new approaches and new problems and I don't mind just going and rolling up my sleeves and trying something new. This research is the culmination of what I thought I wanted to do when I was a graduate student.

Philip Phillips C.V. Highlights

1979: Receives bachelor's degree in math and chemistry from Walla Walla Community College in Washington state

1979–81: Graduate research assistant in theoretical chemistry at the University of Washington, Seattle

1981–84: Miller Postdoctoral Fellowship, University of California, Berkeley

1984–90: Assistant professor of chemistry, Massachusetts Institute of Technology, Cambridge

1990–93: Associate professor, Department of Chemistry, Massachusetts Institute of Technology, Cambridge

1993–99: Associate professor, Department of Physics, University of Illinois, Urbana-Champaign

2000–Present: Professor of physics, Department of Physics, University of Illinois, Urbana-Champaign

A TED talk by Janna Levin

I would like to embed the link to her talk. In this film, she talks of black holes , dynamics of space-time in the form of gravitational waves and the big bang. Especially, she discusses how such things can be heard. She presented to audience some astounding examples. I'm really impressed in the wonders of the pictures she brought there. They were actually made by numerical simulations.
That is marvelous !

Anderson in an interview

He is certainly among the most creative physicists of last century. I find myself resonating with his style in doing physics, with all modesty. This is an excerpt from an interview [http://www.aip.org/history/ohilist/23362_1.html]:

How about quantum electro-dynamics?

ANDERSON:

It was too hard for me. I'm not a formalist. I did listen to some of those lectures. I found the formalism forbidding. I only later came to understand that kind of formalism. I'm lazy. I'm mentally lazy. I believe in using only the tools that are necessary for the job. If I've got a serious problem and it's my problem that I have to solve, I'll go on inventing formalism until I find the answer. But in general I avoid the formalism if I possibly can.

KOJEVNIKOV:

Among other physicists, who do you think is the closest to you in style?

ANDERSON:

Well some of them are experimentalists. I've always thought that Nicolaas Bloembergen and I were very similar. He's half a theorist, or say six tenths experimentalist and four tenths theorist, and I'm more like six tenths theorist and four tenths experimentalist. So that's fairly close. This is immodest of me, and I say this with all modesty, but I think Fermi worked the way I worked. He really was focused on the experimental question. And then he would do formalism if he had to solve it. And Van very much so. Van was no formalist. The reason I was rescued from complete ignorance of formalism was that I had these courses from Schwinger, and so I learned the Green's function formulas and some of that aspect of physics. But that was another thing about the nuclear physics. The Schwinger group of students and the few students who were working with Furry, they were focused on formalism. And I wanted to really explain experimental facts. So when Van gave me this problem—

Anderson and Scalapino talk on Science

This is not a latest news but still interesting for those who are working with cuprate superconductors, which are widely thought to be a central problem faced with by contemporary physicists. The two argue about the possibility of a paring glue. [http://www.sciencemag.org/content/316/5832/1705/reply]

[Anderson]:

I do not, however, accept that Scalapino’s calculations, refined as they are, come near to settling the question he has raised. The numerical analysis of Scalapino’s reference 7, and the analysis of experiments in his references 8 and 9, all have, logically, two pieces. To take ref 7 for definiteness, Scalapino’s group does two computations. The first, while difficult, is logically unimpeachable: It is a carefully designed simulation of the properties of the Hubbard model which we both agree is by far the main Hamiltonian candidate. Sure enough, they find d-wave superconductivity and other physical properties that agree with experiments—and also with much simpler mean field theories (1).

In step 2, they attempt to derive from the measured quantities a number of theoretical constructs, such as the "pairing interaction vertex," assuming that the underlying theory is the conventional Feynman-Dyson diagram theory as adapted for condensed matter problems in the 1960s. Thus, the procedure, far from being a purely direct computational result, is a theoretical construct with a very relevant input of unproven assumptions. The interaction vertex which is derived does not look at all like the J term in the Hamiltonian; it is much smaller than it should be, at high energies, growing to its full strength only at the lowest energies.

This is an unlikely result. It says that somehow all the low-frequency spin fluctuations have killed this giant interaction at the high-frequency end, but left it intact at low frequency to do its work on the pairing gap. It amounts to replacing my "elephant" J with almost nothing but its indirect consequences. It also contradicts the simplest mean field theory of the t-J model (ref 1, called because of its simplicity the "Plain Vanilla" theory).

If I found a result which so blatantly did not make physical sense, I might have questioned the method rather than attacking those of us who seem to have found the right answers by doing things otherwise. It is very attractive to abandon these particular methodological assumptions, because the same set of assumptions, applied in the normal state of the same materials, have had zero success in describing its unique and very anomalous properties.

[Scalapino]:

While there is a growing consensus that superconductivity in the high T_c cuprates arises from strong short-range Coulomb interactions between electrons rather than the traditional electron-phonon interaction, the precise nature of the pairing interaction remains controversial (1). This is the case even among those who agree that the essential physics of the cuprates is contained in the Hubbard model (Perspectives, "Is there glue in cuprate superconductors?", by P. W. Anderson, 22 June 2007, p. 1705). For example, both Anderson’s resonating-valence-based (RVB) theory (2) and the spin-fluctuation exchange theory (3, 4) lead to a short-range interaction which forms d _x²−y² pairs. However, the dynamics of the two interactions differ.

In the RVB picture, the superconducting phase is envisioned as arising out of a Mott-liquid of fluctuating singlet pairs. These pairs are bound by a superexchange interaction J which is proportional to t²/U. Here t is the effective hopping matrix element between adjacent sites and U is an onsite Coulomb interaction. J is determined by the virtual hopping of an electron of a given spin to an adjacent site containing an electron with an opposite spin (5). Thus the dynamics of J involves virtual excitations above the Mott gap which is set by U, and the pairing interaction is essentially instantaneous. In this case, as Anderson recently discussed (6), one would not speak of a pairing glue.

In the spin-fluctuation exchange picture, the pairing is viewed as arising from the exchange of particle-hole spin 1 fluctuations whose dynamics reflect the frequency spectrum seen in inelastic magnetic neutron scattering. This spectrum covers an energy range which is small compared with U or the bare bandwidth 8t. In this case, the pairing interaction is retarded and in analogy to the traditional phonon mediated pairing, one says that the spin-fluctuations provide the pairing glue.

Thus, the question of whether there is pairing glue in the cuprates is a question about the dynamics of the pairing interaction. It offers a way of distinguishing different theories. For the Hubbard model, recent numerical calculations (7) have shown that the strongest pairing occurs for U of order the bandwidth 8t. This is also thought to be the parameter regime appropriate to the cuprates. In this regime, these calculations find that the dynamic dependence of the pairing interaction is the same as that of the dynamic spin susceptibility. Thus, there is pairing glue in the Hubbard model.

Of course, the ultimate question is: What does the experiment tell us about the dynamics of the pairing interaction? Just as the spatial structure of the pairing interaction can be determined from the k-dependence of the superconducting gap, the dynamics of the interaction is reflected in the frequency dependence of the gap. In addition, if the interaction is retarded, that is delayed for a time of order ћ/(2J), the gap will have both a real and an imaginary component. This frequency structure of the gap is reflected in a variety of experiments and analysis of structure in the angular resolved photoemission spectrum (8), and the infrared conductivity (9) have suggested that the dynamics is indeed determined by spin-fluctuations. However, as opposed to the Hubbard model, real materials have phonons and alternative explanations have also been proposed (10). Thus, while there is pairing glue in the Hubbard model, more experimental work is needed to settle the question of whether there is glue in the cuprate superconductors.

Faculty members in conflict with the university president

This story is definitely a reminder of similar things. It involves a famous materials scientist in Tohoku University, Inoue, who also serves as the president of this university. The clouds originate at four papers bearing his name in the 1990s, and could not abate even today, as told by Nature [http://www.nature.com/news/2011/110223/full/470446a.html?WT.ec_id=NATURE-20110224]:

The controversy has been simmering for more than three years, during which critics have repeatedly questioned the results of the four papers^1–4 by Inoue. An internal committee at the university assessed the criticisms and ruled that a formal investigation was not warranted. In the committee's December 2007 report, senior officials questioned whether the criticism was motivated by "malice" and "divorced from a pure concern for academic development". Since then, university faculty members have repeated the criticisms and raised others. But Inoue, a prolific specialist in an unusual form of alloy called metallic glasses, told Nature that his team has unique skills and experience in producing the alloys, which could explain why other scientists have failed to reproduce some of his lab's results.
.......

But in May 2007, a series of anonymous letters began arriving at Tohoku University and other places alleging that the four papers^1–4 co-authored by Inoue in the 1990s contained inconsistencies in the way that the data were presented. The letters also alleged that others in the field had been unable to reproduce the results.

In response to these allegations, Tetsuo Shoji, the university's executive vice-president for research affairs at the time, formed a five-person committee to decide whether a full-scale investigation was warranted. In December 2007, the committee issued a 12-page report that said there were "no rational grounds" for a full investigation. On the problem of irreproducibility, the report said: "various factors including the purity of materials … the cooling method, the protocols, temperature control, moisture control and time control can bring about differences in results, making it easy to imagine how problems in reproducing work might exist among researchers."

Nine metallic-glass experts outside Japan contacted by Nature generally lauded Inoue's contribution to the field. At least one, however, had specifically tried to produce some of the metallic glasses described in the papers^1–4 under discussion but had failed to achieve the large dimensions reported by Inoue. Two others were unable to reproduce other metallic-glass results from Inoue's laboratory.

..........

Omura and other critics also point out, however, that the committee included three people (Shoji, Makoto Watanabe and Keiichi Noe) who had been promoted to their current positions as executive vice-presidents by Inoue since he became university president in 2006. Inoue denies any influence over the committee's make-up. Shoji says that he and other committee members discussed the problem of conflict of interest but decided they would "be able to fairly evaluate the situation". Some critics believe that actual fairness is not enough, and that such a committee must also be seen to be free of any potential conflicts of interest.

In April 2008, university officials rebuffed Omura's letter, defending both the committee's operations and its conclusions.

But in July 2008, 11 researchers from Tohoku's Institute of Multidisciplinary Research for Advanced Materials sent a petition to the university calling for further explanation of the investigating committee's initial report. Attached to the petition was a covering letter by the institute's director, Fumio Saito (who had not signed the petition himself). Then, just over a month later, Saito sent a letter to all university divisions apologizing for implying in his covering letter that the petition expressed "the collective opinion of the institute". Saito's apology added to the controversy.

In yet another twist, in April 2009 a university committee chaired by Inoue temporarily postponed the granting of emeritus status to two retiring faculty members who had been involved with Omura on a website that collects information about the dispute. Emeritus status is customarily granted to retiring professors who have been at the university for at least seven years, as both had been. According to Yukihisa Kitamura, an executive vice-president at Tohoku University, it was a "rare" measure taken while the two were under investigation for allegedly "dishonouring the university" by being involved with the website. In June, with the investigation still under way, the university granted the two emeritus status.

The unrest looks set to continue. During April and May last year, three key science-funding agencies — the science and education ministry, the Science and Technology Agency and the New Energy and Industrial Technology Development Organization — all asked Tohoku University to evaluate accusations raised by Omura and three others. Citing confidentiality rules, a lawyer representing Inoue and Tohoku University declined to say what actions the university would take in response to the requests. Zhang has not responded to Nature 's request for further comment.

..............

Japan has no external body, akin to the US Office of Research Integrity, for investigating alleged scientific misconduct, despite calls for one from some quarters¹⁶. Only the minister of education has authority over a university president, and Kosaku Okada, a representative from the ministry's division familiar with the case, says that the ministry will not get involved. "We see the president as just another scientist and so we leave it up to the university to do any investigation," he says. But an independent investigation may be the only way to silence the critics.

A movie on Einstein

Hi, man, as a fans of him, I'm excited to read this ! I have never seem a film acting this big man's real life. So, it is really a wonderful thing to wait this thing to come. I read a lot of things about Einstein, and I would like to wipe eyes to test my memory.

HSI Films will handle worldwide sales on “Einstein” and immediately introduce the project to distributors in Berlin.

Said Eric Christenson, “Coming aboard a project that teams Wayne Wang and Ron Bass is tremendously exciting, and we have something special on our hands with ‘Einstein.’ People know the name and the theories, yet most people don't know the fascinating details of his life's story.”

Koldo Eguren added, “People don't know about his struggles with poverty, his dyslexia, his love for music, his relationships with the women in his life, his persecution by the Nazis and his battle to deal with living in the public eye and being under constant scrutiny. Ron's screenplay peels back the layers and allows us to see past Einstein the scientist and Einstein the celebrity, showing us Einstein the man.”

Varma's Current

The short review [http://arxiv.org/PS_cache/arxiv/pdf/1012/1012.5461v1.pdf] of the history of High Tc superconductivity by J.Zannen has mentioned the work by C. M.Varma, who proposed the so-called circulating current phase as a candidate explanation of the observed pseudogap phase [http://prl.aps.org/pdf/PRL/v83/i17/p3538_1]. As beautiful as it seems, one should take caution with this: such current is incompatible with the formation of Zhang-Rice singlets. The only claimed experimental support of this phase comes from Neutron scattering and optical experiments which detected a time-reversal symmetry breaking state. However, it might be too hasty to identify this phase with the Varma's phase. Let's wait and see how the holy grail will be won !

Lev Landau

Landau, one of my idols, died 42years ago. He is among the most important physicists in the last century. Here finds a brief tribute to him from Ginzburg.

Landau's occasional abruptness has brought about misconceptions that have become a part (and a rather distorted part) of a legend. I, for instance, have heard people saying, "Landau thinks he is more clever than anyone else." This is completely erroneous, however, and there are many chances for one to see how soberly and modestly Landau assesses his place in science. Many years ago, his love for systematization and clarity led him to classify physicists, by way of a joke, according to the scale of a slide rule. This means that a physicist of second-class standing has achieved ten times less than a physicist of the first class. According to this scale, Albert Einstein, even better than first class, belongs to the 0.5 class, while Niels Bohr, Erwin Schrödinger, Werner Heisenberg, Paul Dirac, Enrico Fermi, and some others belong to the first class. As for himself, Landau used to say that he was in the 2.5 class, and only ten years ago, satisfied with his work, he said he had reached the second class.

Landau's very critical attitude and his opinion that many ideas (or, to be more precise, hints at ideas) are "pathological" spring in a substantial measure from his sober nature and clarity of thinking. His criticism and his denial of certain proposals are always based on scientific grounds and thoroughly deliberated arguments. It is quite a different thing that Landau does not always like to explain his remarks: Often he answers, "Think for yourself." The fact that he is not always ready to answer and explain, however, has nothing in common with conceit or snobbery. A profoundly democratic individual, he is alien to pomposity and respect for rank. Any student could discuss scientific problems with him without difficulty, with the single stipulation that held good for all: The student had to achieve the necessary level of understanding and analyze the problem instead of expecting Landau to think for him and do the things that the student could do himself.

Interview with Roger Penrose

Nature conducted an interview with Professor Roger Penrose, who recently re-captured one's imagination with his consecutive aeons referring to the universe. [http://www.nature.com/nature/journal/v468/n7327/full/4681039a.html]:

You are currently working on a book called Fashion, Faith and Fantasy. What it is about?

I rashly suggested that title for three lectures I gave at Princeton University in 2003. 'Fashion' refers mainly to string theory, which has many merits but is not believable. I don't see how you can make sense of all those extra dimensions. 'Faith' refers to quantum mechanics. It's a wonderful theory and works beautifully, but is self-inconsistent — in my view, when you make a measurement, you violate the Schrödinger equation. At some scale in the Universe, quantum mechanics will have to be replaced by a better theory.

And 'fantasy'?

That's largely directed at cosmic inflation, in which the Universe is supposed to have expanded by an enormous factor just after the Big Bang. I've always been against this — it can only work if you start off in a very special state. In my recent book Cycles of Time, I propose my own fantastical scheme that the entire history of the Universe is just one stage in a succession. What we think of as the Big Bang is not the beginning. It's the continuation of the remote future of a previous aeon.

How might we know if that is true?

The cosmic microwave background — the radiation left over from the Big Bang — would reveal evidence of events taking place in the aeon before ours, mainly encounters between supermassive black holes. When galaxies collide, their central black holes may spiral around and swallow each other up, causing an enormous burst of gravitational radiation. Such a burst from late in the previous aeon would leave its mark as circles around which the temperature is anomalously uniform. My colleague Vahe Gurzadyan sees tentative signs of them [see http://go.nature.com/Lbwiou].

No evidence for the time before Big Bang

Several years ago, Roger Penrose proposed a different cosmological model, which allows the universe to recycle. His considerations are mainly based on two things: (1) The second law of thermodynamics, which states that, the entropy of the universe as an isolated system must increase with time; (2)The conformal invariance, which states that the metric can be determined up to a scale. Point (1) is strong, but (2) is weak. Recently, Roger and his collaborators claimed evidence for their model. This claimed evidence comes from concentric circular belts discernible on the CMB. However, this claim soon intrigues lots of rebuttals. A good review can be found here and here .

Time for Scientists to underpin Wikipedia

Wikipedia, the world's largest online encyclopaedia, is regarded with suspicion by some in the scientific community — perhaps because the wiki model is inconsistent with traditional academic scholarship (Nature 468, 359–360; 2010). But the time has come for scientists to engage more actively with Wikipedia.

Type any scientific term into any search engine and it is likely that a Wikipedia article will be the first hit. Ten years ago, it would have been inconceivable that a free collaborative website, written and maintained by volunteers, would dominate the global provision of knowledge. But Wikipedia is now the first port of call for people seeking information on subjects that include scientific topics. Like it or not, other scientists and the public are using it to get an overview of your specialist area.

Wikipedia's user-friendly global reach offers an unprecedented opportunity for public engagement with science. Scientists who receive public or charitable funding should therefore seize the opportunity to make sure that Wikipedia articles are understandable, scientifically accurate, well sourced and up-to-date.

Many in the scientific community will admit to using Wikipedia occasionally, yet few have contributed content. For society's sake, scientists must overcome their reluctance to embrace this resource. [Nature, 468:765]

Tinkham passed away

Tinkham is famous for his work and his book in superconductivity. He passed away last month. Here is an obituary from Nature: [Nature: 468, 766]

This spectacular role in the early history of the BCS theory behind him, Tinkham continued to work with far-infrared spectroscopy but also began to study the macroscopic quantum behaviour of superconductors. Quantum mechanics is normally thought of as important only in the microscopic world of atoms, but in superconductors it manifests itself in very large objects, such as in the superconducting magnets used in magnetic resonance imaging. After Tinkham took up a professorship in 1966 at Harvard University in Cambridge, Massachusetts, one question emerged that remained of central interest to him: what is the nature and origin of resistance in a superconductor? Or put more simply, when is a superconductor really a superconductor?

As it turns out, when superconductors are carrying a current, they don't stay in a fixed macroscopic quantum state, but cascade down from one energy level to another. As energy is lost with each transition, this is equivalent to saying that superconductors have resistance, although it is extremely small under most conditions. In the latter stages of his career, Tinkham was examining the conditions under which these transitions happen and how they happen in very thin wires of a superconductor.

Despite all these achievements, being elected to the US National Academy of Sciences and winning the prestigious Oliver E. Buckley prize of the American Physical Society, Mike was a modest man with an exceptional sense of humour. The same legions of students who witnessed his alchemy with data will remember how they first knocked nervously on his door to be greeted by a somewhat gruff “Come in”, only to learn that he was a very warm and witty mentor.

Chandra, a great physcist

Mr. Chandra is a groundbreaking physicist, who contributed significantly in various aspects in physics. He was born in 1915 and passed away in 1995. Physics Today in this edit has four articles talking about his life and legacy:

(1)http://ptonline.aip.org/journals/doc/PHTOAD-ft/vol_63/iss_12/38_1.shtml
(2)http://ptonline.aip.org/journals/doc/PHTOAD-ft/vol_63/iss_12/44_1.shtml
(3)http://ptonline.aip.org/journals/doc/PHTOAD-ft/vol_63/iss_12/49_1.shtml
(4) http://ptonline.aip.org/journals/doc/PHTOAD-ft/vol_63/iss_12/57_1.shtml

The last one is written by himself.