Physics ± Uspekhi 53 (12) 1299 ± 1300 (2010) # 2010 Uspekhi Fizicheskikh Nauk, Russian Academy of Sciences
PACS number: 01.90.+g
Physics news on the Internet (based on electronic preprints)
DOI: 10.3367/UFNe.0180.201012d.1330
1. Testing Lorentz invariance 3. Magnetic excitations in cuprate
in decays of K0S mesons superconductors
A de Angelis (Physics Institute of the Max Planck Society, M Greven (University of Minnesota, USA) and his col-
Germany) and his colleagues from Italy have obtained new leagues, using the method of inelastic scattering of spin-
constraints on the hypothetical effect of Lorentz invariance polarized neutrons, found a new type of magnetic waves
violation in K0S ! p pÿ decays. They analyzed 62.3 million (magnetic excitations) characterized by low dispersion in
decay events recorded by the KLOE detector at the DAFNE high-temperature superconducting HgBa2 CuO 4d . The
synchrotron accelerator of the National Laboratory in energy of these excitations ranges from 52 to 56 meV, and
Frascati (Italy) and permitting reliable reconstruction. they are observed at temperatures below the characteristic
Researchers measured the K0S meson lifetime as a function temperature T at which a pseudogap is formed in the electron
of the direction of motion of the Earth relative to the reference spectrum of the material. The study of the pseudogap state is
frame fixed to the microwave background radiation, i.e., the an ever important problem because the mechanism of its
frame in which the microwave background radiation has a generation may hold a clue to the mechanism of high-
zero dipole component. The measured degree of asymmetry, temperature superconductivity. The discovered collective
A ÿ0:13 0:40 10ÿ3 , is compatible with the zero value mode of magnetic excitations is likely to be directly connected
of A 0, i.e., no dependence of the lifetime of K0S mesons on with the pseudogap as the mode's intensity begins to increase
their direction of motion was found at a confidence level of as the material is cooled to temperatures below T . Electron±
95%. This result improves previously calculated upper limits phonon excitation may prove to be the mechanism responsible
by about an order of magnitude. for these excitations. The energy of excitations is close to the
Source: http://arXiv.org/abs/1011.3720vl energy of one of the resonances of the compound HgBa2 -
CuO4d , which explains why they were not observed in earlier
experiments.
2. Heat production in nuclear fuel
Source: Nature 468 283 (2010)
Of the energy generated in nuclear reactors, approximately http://dx.doi.org/10.1038/nature09477
8% is contributed by natural decays of radionuclides, i.e.,
products of the main reactions. Uncertainties still survive in
4. Information is used to increase free energy
the characteristics of these fission processes and their removal
may significantly improve the safety of storing and processing M Sano (University of Tokyo, Japan) and his colleagues have
nuclear materials, plus this may generate an appreciable demonstrated that the free energy of a Brownian particle can
economic gain. The new experiment carried out by an be increased by using information on the direction of its
international team of scientists at the IGISOL isotope velocity. A dimer particle Ð a pair of polystyrene beads
separator of the University of Jyv askyl
a (Finland) studied 287 nm in diameter Ð was fixed to the wall of a chamber
heat release in decays of nuclides 102;104ÿ107 Tc, 105 Mo and filled with buffer solution and could rotate around its axis. A
101
Nb. The total-absorption gamma spectrometer designed at rotating ellipsoidal electric field was created in the chamber,
the B P Konstantinov Petersburg Nuclear Physics Institute which applied torque moment to the particle. Molecules of
was directly coupled to a Penning trap, into which all nuclides the buffer solution caused the particle to execute rotational
generated in the cyclotron were sent, and which recorded the Brownian motion which was monitored through a micro-
total-absorption g-cascades that followed b-decays. For the scope and high-speed video camera. The particle was allowed
nuclei 104ÿ107 Tc and 105 Mo, the amount of decay heat to rotate in the direction of increasing the potential energy
removed by gamma radiation was found to be greater than (against the torque moment), while in the opposite direction
that yielded by earlier measurements with germanium its motion was artificially blocked by changing the phase of
detectors. The new measurements removed much of the the electric field. This created a feedback loop that controlled
uncertainty in energy release in decays of 239 Pu and daughter the motion of the particle by using the information on its
nuclei in the time interval from 4 to 3000 s after the direction. As a result, the particle was raised to a state with
termination of fission in the reactor. The results are also greater and greater potential energy. This process resembles
useful for improving the accuracy of the spectrum of the the thought experiment with `Maxwell's demon', which sorts
antineutrino signal from nuclear reactors, which is important out molecules according to their energy. In terms of
for studying neutrino oscillations. L Szillard's interpretation, information is consumed to
Source: Phys. Rev. Lett. 105 202501 (2010) create a temperature difference, which results in the growth
http://dx.doi.org/10.1103/PhysRevLett.105.202501 of entropy in the compound larger system that includes the
demon itself. Thus, the second law of thermodynamics is not
Uspekhi Fizicheskikh Nauk 180 (12) 1330 (2010) violated here. Quantitative measurements conducted by
DOI: 10.3367/UFNr.0180.201012d.1330 M Sano et al. confirmed the theoretical relations derived by
Translated by V I Kisin C Jarzynski (University of Maryland, USA) that characterize
the efficiency of obtaining the free energy from information.
1300 Physics news on the Internet Physics ± Uspekhi 53 (12)
In this experiment, the demon is a cumbersome system
involving a video camera, computers, and other pieces of
equipment. Moving the whole experiment to the nanoscale
could be the next step, e.g., by creating a microscopic control
system for `molecular motors'.
Source: Nature Physics 6 988 (2010);
http://dx.doi.org/10.1038/nphysl821
5. Massive neutron star
Using the Green Bank radio telescope, P Demorest (National
Radio Astronomy Observatory, USA) and his colleagues
have discovered a neutron star with a record large mass of
1:97 0:04 solar masses. The astronomers studied the PSR
J1614-2230 millisecond pulsar in a binary system at a distance
of about 3000 light years from Earth. A new technique of
coherent filtering of signal fading caused by dispersion in
interstellar gas was utilized. Owing to a favorable orientation
of the plane of orbit (seen from Earth almost perfectly edge-
on), it proved possible to use the timing technique (measure-
ment of pulse rate) for high-precision measurements of the
Shapiro effect, i.e., the delay of signals propagating in a
gravitational field. Taking this effect and the expected
characteristics of the orbital motion into account, the mass
of the neutron star was inferred. Measuring the masses and
radii of neutron stars makes it possible to determine
constraints on the equation of state of matter at the nuclear
densities they consist of. Hypotheses have been advanced on
the presence in neutron stars of an exotic hadron matter Ð
hyperons or kaon condensate. The fact that a neutron star
with a mass of 1:97M does exist rules out these models
and imposes severe constraints on models with quark matter,
without as yet ruling them out completely.
Source: Nature 467 1081 (2010)
http://arXiv.org/abs/1010.5788vl
Compiled by Yu N Eroshenko
(e-mail: erosh@ufn.ru)
