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Type-I superconductivity in noncentrosymmetric superconductor AuBe
The noncentrosymmetric superconductor AuBe have been investigated using the
magnetization, resistivity, specific heat, and muon-spin relaxation/rotation
measurements. AuBe crystallizes in the cubic FeSi-type B20 structure with
superconducting transition temperature observed at = 3.2 0.1 K.
The low-temperature specific heat data, (T), indicate a weakly-coupled
fully gapped BCS superconductivity with an isotropic energy gap
2 = 3.76, which is close to the BCS value of 3.52.
Interestingly, type-I superconductivity is inferred from the SR
measurements, which is in contrast with the earlier reports of type-II
superconductivity in AuBe. The Ginzburg-Landau parameter is = 0.4
1/. The transverse-field SR data transformed in the maximum
entropy spectra depicting the internal magnetic field probability distribution,
P(H), also confirms the absence of the mixed state in AuBe. The thermodynamic
critical field, , calculated to be around 259 Oe. The zero-field SR
results indicate that time-reversal symmetry is preserved and supports a
spin-singlet pairing in the superconducting ground state.Comment: 9 pages, 9 figure
Noncommutative gravity, a `no strings attached' quantum-classical duality, and the cosmological constant puzzle
There ought to exist a reformulation of quantum mechanics which does not
refer to an external classical spacetime manifold. Such a reformulation can be
achieved using the language of noncommutative differential geometry. A
consequence which follows is that the `weakly quantum, strongly gravitational'
dynamics of a relativistic particle whose mass is much greater than Planck mass
is dual to the `strongly quantum, weakly gravitational' dynamics of another
particle whose mass is much less than Planck mass. The masses of the two
particles are inversely related to each other, and the product of their masses
is equal to the square of Planck mass. This duality explains the observed value
of the cosmological constant, and also why this value is nonzero but extremely
small in Planck units.Comment: 7 pages. Second Prize in Gravity Research Foundation Essay
Competition, 2008. Two paragraphs added to original essay to enhance clarity.
To appear in Gen. Rel. Gra
Checking T and CPT violation with sterile neutrino
Post LSND results, sterile neutrinos have drawn attention and motivated the
high energy physics, astronomy and cosmology to probe physics beyond the
standard model considering minimal 3+1 (3 active and 1 sterile) to 3+N neutrino
schemes. The analytical equations for neutrino conversion probabilities are
developed in this work for 3+1 neutrino scheme. Here, we have tried to explore
the possible signals of T and CPT violations with four flavor neutrino scheme
at neutrino factory. Values of sterile parameters considered in this analysis
are taken from two different types of neutrino experiments viz. long baseline
experiments and reactor+atmospheric experiments. In this work golden and
discovery channels are selected for the investigation of T violation. While
observing T violation we stipulate that neutrino factory working at 50 GeV
energy have the potential to observe the T violation signatures for the
considered range of baselines(3000 km-7500 km). The ability of neutrino factory
for constraining CPT violation is enhanced with increase in energy for normal
neutrino mass hierarchy(NH). Neutrino factory with the exposure time of 500
kt-yr will be able to capture CPT violation with GeV at 3 level for NH and for IH with GeV at 3 level
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