95 research outputs found
Pengaruh Pengumuman Indonesia Sustainability Reporting Award (Isra) Terhadap Abnormal Return Dan Volume Perdagangan Saham (Studi Kasus Pada Perusahaan Peraih Penghargaan Isra 2009-2010)
This research studies the impact of Indonesia Sustainability Reporting Award (ISRA) announcementto abnormal return and trading value activity. The impact of award publication could be seenfrom whether there are some differences between abnormal return and trading value activitybefore and after ISRA announcement. The research samples are 16 companies which acceptedthe appreciation of ISRA period 2009-2010. The research data that used is secondary data thatconsist of daily closing price of shares and daily trading volume with an event period 5 days beforeannouncement and 5 days after announcement by used a market adjusted model for expectedreturn. Hypothese are tested by paired samples t-test. The result of this research proves that thereis no difference abnormal return before and after ISRA 2009-2010 announcement, Trading valueactivity have no difference before and after ISRA 2009-2010 announcement
Spin-current modulation and square-wave transmission through periodically stubbed electron waveguides
Ballistic spin transport through waveguides, with symmetric or asymmetric
double stubs attached to them periodically, is studied systematically in the
presence of a weak spin-orbit coupling that makes the electrons precess. By an
appropriate choice of the waveguide length and of the stub parameters injected
spin-polarized electrons can be blocked completely and the transmission shows a
periodic and nearly square-type behavior, with values 1 and 0, with wide gaps
when only one mode is allowed to propagate in the waveguide. A similar behavior
is possible for a certain range of the stub parameters even when two-modes can
propagate in the waveguide and the conductance is doubled. Such a structure is
a good candidate for establishing a realistic spin transistor. A further
modulation of the spin current can be achieved by inserting defects in a
finite-number stub superlattice. Finite-temperature effects on the spin
conductance are also considered.Comment: 19 pages, 8 figure
Resonance Patterns of an Antidot Cluster: From Classical to Quantum Ballistics
We explain the experimentally observed Aharonov-Bohm (AB) resonance patterns
of an antidot cluster by means of quantum and classical simulations and Feynman
path integral theory. We demonstrate that the observed behavior of the AB
period signals the crossover from a low B regime which can be understood in
terms of electrons following classical orbits to an inherently quantum high B
regime where this classical picture and semiclassical theories based on it do
not apply.Comment: 5 pages revtex + 2 postscript figure
Ballistic electron transport in stubbed quantum waveguides: experiment and theory
We present results of experimental and theoretical investigations of electron
transport through stub-shaped waveguides or electron stub tuners (ESTs) in the
ballistic regime. Measurements of the conductance G as a function of voltages,
applied to different gates V_i (i=bottom, top, and side) of the device, show
oscillations in the region of the first quantized plateau which we attribute to
reflection resonances. The oscillations are rather regular and almost periodic
when the height h of the EST cavity is small compared to its width. When h is
increased, the oscillations become less regular and broad depressions in G
appear. A theoretical analysis, which accounts for the electrostatic potential
formed by the gates in the cavity region, and a numerical computation of the
transmission probabilities successfully explains the experimental observations.
An important finding for real devices, defined by surface Schottky gates, is
that the resonance nima result from size quantization along the transport
direction of the EST.Comment: Text 20 pages in Latex/Revtex format, 11 Postscript figures. Phys.
Rev. B,in pres
Coulomb suppression of NMR coherence peak in fullerene superconductors
The suppressed NMR coherence peak in the fullerene superconductors is
explained in terms of the dampings in the superconducting state induced by the
Coulomb interaction between conduction electrons. The Coulomb interaction,
modelled in terms of the onsite Hubbard repulsion, is incorporated into the
Eliashberg theory of superconductivity with its frequency dependence considered
self-consistently at all temperatures. The vertex correction is also included
via the method of Nambu. The frequency dependent Coulomb interaction induces
the substantial dampings in the superconducting state and, consequently,
suppresses the anticipated NMR coherence peak of fullerene superconductors as
found experimentally.Comment: 4 pages, Revtex, and 2 figures. Revised and final version to appear
in Phys. Rev. Lett. (1998
Imaging Fractal Conductance Fluctuations and Scarred Wave Functions in a Quantum Billiard
We present scanning-probe images and magnetic-field plots which reveal
fractal conductance fluctuations in a quantum billiard. The quantum billiard is
drawn and tuned using erasable electrostatic lithography, where the scanning
probe draws patterns of surface charge in the same environment used for
measurements. A periodicity in magnetic field, which is observed in both the
images and plots, suggests the presence of classical orbits. Subsequent
high-pass filtered high-resolution images resemble the predicted probability
density of scarred wave functions, which describe the classical orbits.Comment: 5 pages, 4 figures To be published in PR
Geometry-dependent scattering through quantum billiards: Experiment and theory
We present experimental studies of the geometry-specific quantum scattering
in microwave billiards of a given shape. We perform full quantum mechanical
scattering calculations and find an excellent agreement with the experimental
results. We also carry out the semiclassical calculations where the conductance
is given as a sum of all classical trajectories between the leads, each of them
carrying the quantum-mechanical phase. We unambiguously demonstrate that the
characteristic frequencies of the oscillations in the transmission and
reflection amplitudes are related to the length distribution of the classical
trajectories between the leads, whereas the frequencies of the probabilities
can be understood in terms of the length difference distribution in the pairs
of classical trajectories. We also discuss the effect of non-classical "ghost"
trajectories that include classically forbidden reflection off the lead mouths.Comment: 4 pages, 4 figure
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