135,722 research outputs found
Ku-band field-effect power transistors
A single stage amplifier was developed using an 8 gate, 1200 micrometer width device to give a gain of 3.3 + or - 0.1 dB over the 14.4 to 15.4 GHz band with an output power of 0.48 W and 15% minimum efficiency with 0.255 W of input power. With two 8 gate devices combined and matched on the device carrier, using a lumped element format, a gain of 3 dB was attained over the 14.5 to 15.5 GHz band with a maximum efficiency of 9.9% for an output power of 0.8 W
Transverse momentum dependence in the perturbative calculation of pion form factor
By reanalysing transverse momentum dependence in the perturbative calculation
of pion form factor an improved expression of pion form factor which takes into
account the transverse momentum dependenc in hard scattering amplitude and
intrinsic transverse momentum dependence associated with pion wave functions is
given to leading order, which is available for momentum transfers of the order
of a few GeV as well as for . Our scheme can be extended to
evaluate the contributions to the pion form factor beyond leading order.Comment: 13 pages in LaTeX, plus 3 Postscript figure
Weak gravity conjecture constraints on inflation
We consider the gravitational correction to the coupling of the scalar
fields. Weak gravity conjecture says that the gravitational correction to the
running of scalar coupling should be less than the contribution from scalar
fields. For instance, a new scale sets a UV cutoff
on the validity of the effective theory. Furthermore, this
conjecture implies a possible constraint on the inflation model, e.g. the
chaotic inflation model might be in the swampland.Comment: 11 pages, 3 figs; monor corrections; some clarifying remarks added
and the final version for publication in JHE
The Differences of Star Formation History Between Merging Galaxies and Field Galaxies in the EDR of the SDSS
Based on the catalog of merging galaxies in the Early Data Release (EDR) of
the Sloan Digital Sky Survey (SDSS), the differences of star formation history
between merging galaxies and field galaxies are studied statistically by means
of three spectroscopic indicators the 4000-\r{A} break strength, the Balmer
absorption-line index, and the specific star formation rate. It is found that
for early-type merging galaxies the interactions will not induce significant
enhancement of the star-formation activity because of its stability and lack of
cool gas. On the other hand, late-type merging galaxies always in general
display more active star formation than field galaxies on different timescales
within about 1Gyr. We also conclude that the mean stellar ages of late-type
merging galaxies are younger than those of late-type field galaxies.Comment: 9 pages, 4 figures, accepted for publication in PAS
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