1,994 research outputs found
Petrology and tectonic development of supracrustal sequence of Kerala Khondalite Belt, Southern India
The granulite terrain of southern India, of which the Kerala Khondalite belt (KKB) is a part, is unique in exposing crustal sections with arrested charnockite growth in different stages of transformation and in varied lithological association. The KKB with rocks of surficial origin and incipient charnockite development, poses several problems relating to the tectonics of burial of vast area and mechanisms involved in expelling initial H2O (causes of dryness) for granulite facies metamorphism. It is possible to infer the following sequence of events based on the field and laboratory studies: (1) derivation of protoliths of KKB from granitic uplands and deposition in fault bounded basin (cratonic rift); (2) subhorizontal deep burial of sediments; (3) intense deformation of infra and supracrustal rocks; (4) early granulite facies metamorphism predating F sub 2 - loss of primary structure in sediments and formation of charnockites from amphibole bearing gneisses and khondalites from pelites; (5) migmatisation and deformation of metasediments and gneisses; (6) second event of charnockite formation probably aided by internal CO2 build-up; and (7) isothermal uplift, entrapment of late CO2 and mixed CO2-H2O fluids, formation of second generation cordierites and cordierite symplectites
Self-consistent variational approach to the minimal left-right symmetric model of electroweak interactions
The problem of mass generation is addressed by a Gaussian variational method
for the minimal left-right symmetric model of electroweak interactions. Without
any scalar bidoublet, the Gaussian effective potential is shown to have a
minimum for a broken symmetry vacuum with a finite expectation value for both
the scalar Higgs doublets. The symmetry is broken by the fermionic coupling
that destabilizes the symmetric vacuum, yielding a self consistent fermionic
mass. In this framework a light Higgs is only compatible with the existence of
a new high energy mass scale below 2 TeV.Comment: 5 pages, 3 figures. New comments added and typing errors in eq. 8 and
11 correcte
First principles investigation of finite-temperature behavior in small sodium clusters
A systematic and detailed investigation of the finite-temperature behavior of
small sodium clusters, Na_n, in the size range of n= 8 to 50 are carried out.
The simulations are performed using density-functional molecular-dynamics with
ultrasoft pseudopotentials. A number of thermodynamic indicators such as
specific heat, caloric curve, root-mean-square bond length fluctuation,
deviation energy, etc. are calculated for each of the clusters. Size dependence
of these indicators reveals several interesting features. The smallest clusters
with n= 8 and 10, do not show any signature of melting transition. With the
increase in size, broad peak in the specific heat is developed, which
alternately for larger clusters evolves into a sharper one, indicating a
solidlike to liquidlike transition. The melting temperatures show irregular
pattern similar to experimentally observed one for larger clusters [ M. Schmidt
et al., Nature (London) 393, 238 (1998) ]. The present calculations also reveal
a remarkable size-sensitive effect in the size range of n= 40 to 55. While
Na_40 and Na_55 show well developed peaks in the specific heat curve, Na_50
cluster exhibits a rather broad peak, indicating a poorly-defined melting
transition. Such a feature has been experimentally observed for gallium and
aluminum clusters [ G. A. Breaux et al., J. Am. Chem. Soc. 126, 8628 (2004); G.
A.Breaux et al., Phys. Rev. Lett. 94, 173401 (2005) ].Comment: 8 pages, 11 figure
Water activities in the Kerala Khondalite Belt
The author and colleagues presented their determinations of water activities in various granulite-facies rocks of the Kerala Khondalite Belt. Using mineral equilibria, thermodynamic data, and assumed geopressure-geotemperature conditions of 5.5 kbar and 750 C, they calculated uniformly low a(H2O) values of about 0.27 over a large geographic region. They suggested that these conditions were produced by the presence of abundant CO2-rich fluids, derived either from deeper levels or from metamorphic reactions involving graphite
Supersymmetry in Slow Motion
We construct new theories of electroweak symmetry breaking that employ a
combination of supersymmetry and discrete symmetries to stabilize the weak
scale up to and beyond the energies probed by the LHC. These models exhibit
conventional supersymmetric spectra but the fermion-sfermion-gaugino vertices
are absent. This closes many conventional decay channels, thereby allowing
several superpartners to be stable on collider time scales. This opens the door
to the possibility of directly observing R-hadrons and three flavors of
sleptons inside the LHC detectors.Comment: A reference added. The discussion on the Higgs sector expanded. The
version accepted for publication in JHE
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The Little Hierarchy in Universal Extra Dimensions
In the standard model in universal extra dimensions (UED) the mass of the
Higgs field is driven to the cutoff of the higher-dimensional theory. This
re-introduces a small hierarchy since the compactification scale 1/R should not
be smaller than the weak scale. In this paper we study possible solutions to
this problem by considering five-dimensional theories where the Higgs field
potential vanishes at tree level due to a global symmetry. We consider two
avenues: a Little Higgs model and a Twin Higgs model. An obstacle for the
embedding of these four-dimensional models in five dimensions is that their
logarithmic sensitivity to the cutoff will result in linear divergences in the
higher dimensional theory. We show that, despite the increased cutoff
sensitivity of higher dimensional theories, it is possible to control the Higgs
mass in these two scenarios. For the Little Higgs model studied, the
phenomenology will be significantly different from the case of the standard
model in UED. This is due to the fact that the compactification scale
approximately coincides with the scale where the masses of the new states
appear. For the case of the Twin Higgs model, the compactification scale may be
considerably lower than the scale where the new states appear. If it is as low
as allowed by current limits, it would be possible to experimentally observe
the standard model Kaluza-Klein states as well as a new heavy quark. On the
other hand, if the compactification scale is higher, then the phenomenology at
colliders would coincide with the one for the standard model in UED.Comment: 25 pages, 2 figure
Implications on SUSY breaking mediation mechanisms from observing and the muon
We consider and the muon in various SUSY
breaking mediation mechanisms. If the decay is observed
at Tevatron Run II with a branching ratio larger than ,
the noscale supergravity (including the gaugino mediation), the gauge mediation
scenario with small number of messenger fields and low messenger scale, and a
class of anomaly mediation scenarios will be excluded, even if they can
accommodate a large muon . On the other hand, the minimal
supergravity scenario and similar mechanisms derived from string models can
accommodate this observation.Comment: 4 pages, 3 figure
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