2,685 research outputs found
Effective Superpotentials for SO/Sp with Flavor from Matrix Models
We study matrix models related to gauge theories with flavors. We
give the effective superpotentials for gauge theories with arbitrary tree level
superpotential up to first instanton level. For quartic tree level
superpotential we obtained exact one-cut solution. We also derive
Seiberg-Witten curve for these gauge theories from matrix model argument.Comment: 17pp,2 figures, v2;refs added and to appear in MPL
Far-ultraviolet Emission-line Morphologies of the Supernova Remnant G65.3+5.7
We present the first far-ultraviolet (FUV) emission-line morphologies of the
whole region of the supernova remnant (SNR) G65.3+5.7 using the FIMS/SPEAR
data. The morphologies of the C IV {\lambda}{\lambda}1548, 1551, He II
{\lambda}1640, and O III] {\lambda}{\lambda}1661, 1666 lines appear to be
closely related to the optical and/or soft X-ray images obtained in previous
studies. Dramatic differences between the C IV morphology and the optical [O
III] {\lambda}5007 image provide clues to a large resonant-scattering region
and a foreground dust cloud. The FUV morphologies also reveal the overall
distribution of various shocks in different evolutionary phases and an
evolutionary asymmetry between the east and the southwest sides in terms of
Galactic coordinates, possibly due to a Galactic density gradient in the global
scale. The relative X-ray luminosity of G65.3+5.7 to C IV luminosity is
considerably lower than those of the Cygnus Loop and the Vela SNRs. This
implies that G65.3+5.7 has almost evolved into the radiative stage in the
global sense and supports the previous proposal that G65.3+5.7 has lost its
bright X-ray shell and become a member of mixed-morphology SNRs as it has
evolved beyond the adiabatic stage.Comment: 6 pages, 3 figures, accepted for publication in The Ap
Tunnelling between non-centrosymmetric superconductors with significant spin-orbit splitting studied theoretically within a two-band treatment
Tunnelling between non-centrosymmetric superconductors with significant
spin-orbit splitting is studied theoretically in a two-band treatment of the
problem. We find that the critical Josephson current may be modulated by
changing the relative angle between the vectors describing absence of inversion
symmetry on each side of the junction. The presence of two gaps also results in
multiple steps in the quasiparticle current-voltage characteristics. We argue
that both these effects may help to determine the pairing states in materials
like CePtSi, UIr and CdReO. We propose experimental tests of
these ideas, including scanning tunnelling microscopy.Comment: 5 pages, 1 figure. Minor changes. Some new references added.
Journal-ref. adde
Using Josephson junctions to determine the pairing state of superconductors without crystal inversion symmetry
Theoretical studies of a planar tunnel junction between two superconductors
with antisymmetric spin-orbit coupling are presented. The half-space Green's
function for such a superconductor is determined. This is then used to derive
expressions for the dissipative current and the Josephson current of the
junction. Numerical results are presented in the case of the Rashba spin-orbit
coupling, relevant to the much studied compound CePtSi. Current-voltage
diagrams, differential conductance and the critical Josephson current are
presented for different crystallographic orientations and different weights of
singlet and triplet components of the pairing state. The main conclusion is
that Josephson junctions with different crystallographic orientations may
provide a direct connection between unconventional pairing in superconductors
of this kind and the absence of inversion symmetry in the crystal.Comment: 16 pages, 10 figure
Analysis of Spatial Structure of the SPica H II Region
Far ultraviolet (FUV) spectral images of the Spica H II region are first
presented here for the Si II* 1533.4A and Al II 1670.8A lines and then compared
with the optical Halpha image. The H alpha and Si II* images show enhanced
emissions in the southern part of the H II region where H I density increases
outwards. This high density region, which we identify as part of the
"interaction ring" of the Loop I superbubble and the Local Bubble, seems to
bound the southern H II region. On the other hand, the observed profile of Al
II shows a broad central peak, without much difference between the northern and
southern parts, which we suspect results from multiple resonant scattering. The
extended tails seen in the radial profiles of the FUV intensities suggest that
the nebula may be embedded in a warm ionized gas. Simulation with a spectral
synthesis code yields the values of the Lyman continuum luminosity and the
effective temperature of the central star similar to previous estimates with
10^46.2 photons s^-1 and 26,000 K, respectively, but the density of the
northern H II region, 0.22 cm^-3, is much smaller than previous estimates for
the H alpha brightest region.Comment: 15 pages, 5 figures, accepted for Ap
NMR relaxation rate in non-centrosymmetric superconductors
The spin-lattice relaxation rate of nuclear magnetic resonance in a clean
superconductor without inversion center is calculated for arbitrary pairing
symmetry and band structure, in the presence of strong spin-orbit coupling.Comment: 4 page
Spin fluctuations and superconductivity in noncentrosymmetric heavy fermion systems CeRhSi and CeIrSi
We study the normal and the superconducting properties in noncentrosymmetric
heavy fermion superconductors CeRhSi and CeIrSi. For the normal state,
we show that experimentally observed linear temperature dependence of the
resistivity is understood through the antiferromagnetic spin fluctuations near
the quantum critical point (QCP) in three dimensions. For the superconducting
state, we derive a general formula to calculate the upper critical field
, with which we can treat the Pauli and the orbital depairing effect on
an equal footing. The strong coupling effect for general electronic structures
is also taken into account. We show that the experimentally observed features
in , the huge value up to 30(T), the downward
curvatures, and the strong pressure dependence, are naturally understood as an
interplay of the Rashba spin-orbit interaction due to the lack of inversion
symmetry and the spin fluctuations near the QCP. The large anisotropy between
and is explained in terms of
the spin-orbit interaction. Furthermore, a possible realization of the
Fulde-Ferrell- Larkin-Ovchinnikov state for is studied. We
also examine effects of spin-flip scattering processes in the pairing
interaction and those of the applied magnetic field on the spin fluctuations.
We find that the above mentioned results are robust against these effects. The
consistency of our results strongly supports the scenario that the
superconductivity in CeRhSi and CeIrSi is mediated by the spin
fluctuations near the QCP.Comment: 21pages, 13figures, to be published in Phys. Rev.
SPEAR Far Ultraviolet Spectral Images of the Cygnus Loop
We present far-ultraviolet (FUV) spectral images, measured at C IV 1550, He
II 1640, Si IV+O IV] 1400, and O III] 1664, of the entire Cygnus Loop, observed
with the Spectroscopy of Plasma Evolution from Astrophysical Radiation (SPEAR)
instrument, also known as FIMS. The spatial distribution of FUV emission
generally corresponds with a limb-brightened shell, and is similar to optical,
radio and X-ray images. The features found in the present work include a
``carrot'', diffuse interior, and breakout features, which have not been seen
in previous FUV studies. Shock velocities of 140-160 km/s is found from a line
ratio of O IV] to O III], which is insensitive not only to resonance scattering
but also to elemental abundance. The estimated velocity indicates that the fast
shocks are widespread across the remnant. By comparing various line ratios with
steady-state shock models, it is also shown that the resonance scattering is
widespread.Comment: 13 pages, 3 figures, 1 table, accepted for publication in ApJ
Prepotential and Instanton Corrections in N=2 Supersymmetric SU(N_1)xSU(N_2) Yang Mills Theories
In this paper we analyse the non-hyperelliptic Seiberg-Witten curves derived
from M-theory that encode the low energy solution of N=2 supersymmetric
theories with product gauge groups. We consider the case of a SU(N_1)xSU(N_2)
gauge theory with a hypermultiplet in the bifundamental representation together
with matter in the fundamental representations of SU(N_1) and SU(N_2). By means
of the Riemann bilinear relations that hold on the Riemann surface defined by
the Seiberg--Witten curve, we compute the logarithmic derivative of the
prepotential with respect to the quantum scales of both gauge groups. As an
application we develop a method to compute recursively the instanton
corrections to the prepotential in a straightforward way. We present explicit
formulas for up to third order on both quantum scales. Furthermore, we extend
those results to SU(N) gauge theories with a matter hypermultiplet in the
symmetric and antisymmetric representation. We also present some non-trivial
checks of our results.Comment: 21 pages, 2 figures, minor changes and references adde
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