7,669 research outputs found
On the production mechanism of radio-pulses from large extensive air showers
None of the theories put forward so far to explain the radio emission from cosmic ray showers, has been successful in giving a satisfactory explanation for all the experimental data obtained from various laboratories over the globe. It is apprehended that emission mechanism at low and high frequencies may be quite different. This calls for new theoretical look into the phenomenon. Theoretical as well as the experimental results indicate that the frequency spectrum is rather flat in the frequency range (40 to 60 MHz. Above 80 MHz, the radio emission can be explained with the help of geomagnetic mechanism. But at very low frequency ( 10 MHz), mechanisms other than geomagnetic are involved
A new study on the emission of EM waves from large EAS
A method used in locating the core of individual cosmic ray showers is described. Using a microprocessor-based detecting system, the density distribution and hence, energy of each detected shower was estimated
Microprocessor-based single particle calibration of scintillation counter
A microprocessor-base set-up is fabricated and tested for the single particle calibration of the plastic scintillator. The single particle response of the scintillator is digitized by an A/D converter, and a 8085 A based microprocessor stores the pulse heights. The digitized information is printed. Facilities for CRT display and cassette storing and recalling are also made available
Non-destructive Orthonormal State Discrimination
We provide explicit quantum circuits for the non-destructive deterministic
discrimination of Bell states in the Hilbert space , where is
qudit dimension. We discuss a method for generalizing this to non-destructive
measurements on any set of orthogonal states distributed among parties.
From the practical viewpoint, we show that such non-destructive measurements
can help lower quantum communication complexity under certain conditions.Comment: 11 pages, 6 fugure
DC field induced enhancement and inhibition of spontaneous emission in a cavity
We demonstrate how spontaneous emission in a cavity can be controlled by the
application of a dc field. The method is specially suitable for Rydberg atoms.
We present a simple argument for the control of emission.Comment: 3-pages, 2figure. accepted in Phys. Rev.
Comment on Quantum teleportation via GHZ-like state
Recently Yang et al. [Int. J. Theo. Phys. 48 (2009) 516] have shown that an
unknown qubit can be teleported by using a particular GHZ-like state as quantum
channel. However, there are several errors in the calculation which lead to
incorrect conclusions. The errors have been indicated and corrected. It is also
noted that their scheme and the independently proposed teleportation scheme of
Zhang et al. [Int. J. Theo. Phys. 48 (2009) 3331] uses quantum channel from the
same family and any state of that family may be used for teleportation.Comment: 2 page
Enhanced grain surface effect on magnetic properties of nanometric La0.7Ca0.3MnO3 manganite : Evidence of surface spin freezing of manganite nanoparticles
We have investigated the effect of nanometric grain size on magnetic
properties of single phase, nanocrystalline, granular La0.7Ca0.3MnO3 (LCMO)
sample. We have considered core-shell structure of our LCMO nanoparticles,
which can explain its magnetic properties. From the temperature dependence of
field cooled (FC) and zero-field cooled (ZFC) dc magnetization (DCM), the
magnetic properties could be distinguished into two regimes: a relatively high
temperature regime T > 40 K where the broad maximum of ZFC curve (at T = Tmax)
is associated with the blocking of core particle moments, whereas the sharp
maximum (at T = TS) is related to the freezing of surface (shell) spins. The
unusual shape of M (H) loop at T = 1.5 K, temperature dependent feature of
coercive field and remanent magnetization give a strong support of surface spin
freezing that are occurring at lower temperature regime (T < 40 K) in this LCMO
nanoparticles. Additionally, waiting time (tw) dependence of ZFC relaxation
measurements at T = 50 K show weak dependence of relaxation rate [S(t)] on tw
and dM/dln(t) following a logarithmic variation on time. Both of these features
strongly support the high temperature regime to be associated with the blocking
of core moments. At T = 20 K, ZFC relaxation measurements indicates the
existence of two different types of relaxation processes in the sample with
S(t) attaining a maximum at the elapsed time very close to the wait time tw =
1000 sec, which is an unequivocal sign of glassy behavior. This age-dependent
effect convincingly establish the surface spin freezing of our LCMO
nanoparticles associated with a background of superparamagnetic (SPM) phase of
core moments.Comment: 41 pages, 10 figure
Isgur-Wise function in a QCD potential model with coulombic potential as perturbation
We study heavy light mesons in a QCD inspired quark model with the Cornell
potential. Here we consider the linear term
as the parent and i.e.the Coloumbic part as the
perturbation.The linear parent leads to Airy function as the unperturbed
wavefunction. We then use the Dalgarno method of perturbation theory to obtain
the total wavefunction corrected upto first order with Coulombic peice as the
perturbation.With these wavefunctions, we study the Isgur-Wise function and
calculate its slope and curvature.Comment: paper has been modified in Airy functions calculation upto o(r^3
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