2,455 research outputs found
Vanishing DC holographic conductivity from a magnetic monopole condensate
We show how to obtain a vanishing DC conductivity in 3-dimensional strongly
coupled QFT's using a massive 2-form field in the bulk that satisfies a special
kind of boundary condition. The real and imaginary parts of the AC conductivity
are evaluated in this holographic setup and we show that the DC conductivity
identically vanishes even for an arbitrarily small (though nonzero) value of
the 2-form mass in the bulk. We identify the bulk action of the massive 2-form
with an effective theory describing a phase in which magnetic monopoles have
condensed in the bulk. Our results indicate that a condensate of magnetic
monopoles in a 4-dimensional bulk leads to a vanishing DC holographic
conductivity in 3-dimensional strongly coupled QFT's.Comment: 24 pages, 2 figures, accepted for publication in JHE
Renormalization aspects of N=1 Super Yang-Mills theory in the Wess-Zumino gauge
The renormalization of N=1 Super Yang-Mills theory is analysed in the
Wess-Zumino gauge, employing the Landau condition. An all orders proof of the
renormalizability of the theory is given by means of the Algebraic
Renormalization procedure. Only three renormalization constants are needed,
which can be identified with the coupling constant, gauge field and gluino
renormalization. The non-renormalization theorem of the gluon-ghost-antighost
vertex in the Landau gauge is shown to remain valid in N=1 Super Yang-Mills.
Moreover, due to the non-linear realization of the supersymmetry in the
Wess-Zumino gauge, the renormalization factor of the gauge field turns out to
be different from that of the gluino. These features are explicitly checked
through a three loop calculation.Comment: 15 pages, minor text improvements, references added. Version accepted
for publication in the EPJ
Implementing the Gribov-Zwanziger framework in N=1 Super Yang-Mills in the Landau gauge
The Gribov-Zwanziger framework accounting for the existence of Gribov copies
is extended to N=1 Super Yang--Mills theories quantized in the Landau gauge. We
show that the restriction of the domain of integration in the Euclidean
functional integral to the first Gribov horizon can be implemented in a way to
recover non-perturbative features of N=1 Super Yang--Mills theories, namely:
the existence of the gluino condensate as well as the vanishing of the vacuum
energy.Comment: 19 pages, no figure
Orbital order-disorder transition in La(1-x)Nd(x)MnO(3) (x = 0.0-1.0) and La(1-x-y)Nd(yx)Sr(y)MnO(3) (x = 0.1; y = 0.05,0.1)
The nature of orbital order-disorder transition has been studied in the
La(1-x)Nd(x)MnO(3) (x = 0.0-1.0) series which covers the entire range between
two end points - LaMnO(3) and NdMnO(3) - as well as in
La(0.85)Nd(0.1)Sr(0.05)MnO(3) and La(0.8)Nd(0.1)Sr(0.1)MnO(3). It has been
observed that the first-order nature of the transition gives way to higher
order with the increase in "x" in the case of pure manganites. The latent heat
(L) associated with the transition, first, drops with a steeper slope within x
= 0.0-0.3 and, then, gradually over a range 0.3<x<0.9. This drop could,
possibly, be due to evolution of finer orbital domain structure with "x". In
the case of Sr-doped samples, the transition appears to be of higher-order
nature even for a doping level 5 at%. In both cases, of course, the transition
temperature T(JT) rises systematically with the drop in average A-site radius
or rise in average Mn-O-Mn bond bending angle while no
apparent correlation could be observed with doping induced disorder sigma^2.
The cooperative nature of the orbital order, therefore, appears to be robust.Comment: 15 pages including 4 figures; pdf onl
Deformation pattern around the Conejera fault blocks (Asturian Basin, North Iberian Margin)
The Asturian Basin is located on the coastline of the North Iberian Margin. This basin is dissected by long-lived E-, NE- and NW-striking faults that delineate a series of extensional fault blocks that became shortened during the Upper Cretaceous to Cenozoic Alpine convergence. In the Conejera cove, the NE-striking and SE-dipping Conejera Fault displays a remarkable example of contractional deformation, promoted by the mechanical contrast within the Lower to Middle Jurassic stratigraphic series. Field observations and structural analysis carried out in this study reveal: i) a first system of orthogonal cross-joints oblique to the Conejera Fault and other major onshore boundary faults, ii) a second system of meso-extensional faults parallel to the Conejera Fault, and developed by the reactivation and linkage of the orthogonal cross-joints and iii) a series of contractional folds, thrusts and pressure solution with a predominant NE to ENE trend. Observed relationships and structural analysis suggest an obliquity between the here inferred direction of the Late Jurassic-Early Cretaceous stretching (i.e. about N015E) and the onshore boundary faults, whereas the contractional structures are broadly parallel to the NE-striking Conejera Fault and suggest a roughly SSE- to SE-oriented Alpine convergence
Unconventional Metallic Magnetism in LaCrSb{3}
Neutron-diffraction measurements in LaCrSb{3} show a coexistence of
ferromagnetic and antiferromagnetic sublattices below Tc=126 K, with ordered
moments of 1.65(4) and 0.49(4) Bohr magnetons per formula unit, respectively
(T=10 K), and a spin reorientation transition at ~95 K. No clear peak or step
was observed in the specific heat at Tc. Coexisting localized and itinerant
spins are suggested.Comment: PRL, in pres
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