1,403 research outputs found
Spherical collapse of a heat conducting fluid in higher dimensions without horizon
We consider a scenario where the interior spacetime,described by a heat
conducting fluid sphere is matched to a Vaidya metric in higher
dimensions.Interestingly we get a class of solutions, where following heat
radiation the boundary surface collapses without the appearance of an event
horizon at any stage and this happens with reasonable properties of matter
field.The non-occurrence of a horizon is due to the fact that the rate of mass
loss exactly counterbalanced by the fall of boundary radius.Evidently this
poses a counter example to the so-called cosmic censorship hypothesis.Two
explicit examples of this class of solutions are also given and it is observed
that the rate of collapse is delayed with the introduction of extra
dimensions.The work extends to higher dimensions our previous investigation in
4D.Comment: 6 page
Biochemically Induced Variations During Some Phenological Stages in Thompson Seedless Grapevines Grafted on Different Rootstocks
Phenological variation in Thompson Seedless grapevines grafted on different rootstocks and own rootedvines was assessed for two consecutive years and the reasons for such variations were studied throughbiochemical analysis. Uniform and early bud sprouting was recorded in the vines grafted on 110Rrootstock and on own roots, which was attributed to increased peroxidase activity and protein content inthe buds before bud burst. Increased fruitfulness on 110R rootstock and own rooted vines was attributedto the increased phosphorus and protein content of those vines and reduced vegetative vigour measuredin terms of shoot length, cane diameter and pruned biomass. Thompson Seedless grafted on Dogridgerootstock recorded the highest nitrogen content, increased shoot length, cane diameter and increasedpruned biomass attributing to reduced fruitfulness. The highest concentration of phenolic compoundsand amino acids was recorded in the fruits produced on 110R rootstock, while it was least on St. Georgeand own roots. Significant variation in the accumulation pattern of amino acids (especially proline andarginine) was observed, with the least proline/arginine ratio recorded on 110R rootstocks at the time ofharvest, indicating the variation in the days taken for fruit ripening on different rootstocks
Gauged Lifshitz scalar field theories in two dimensions
We present two-dimensional gauged Lifshitz scalar field theories by
considering the duality relation between the source current and the Noether
current. Requiring the duality partially, we obtain a gauged model which
recovers the bosonized Schwinger model for the IR limit. For the exact duality,
however, the source current is not conserved, which means that the resulting
theory is anomalous, so that the number of degrees of freedom is increased. The
second model is consistently formulated by adding the Wess-Zumino type action
to maintain the gauge invariance.Comment: 11 page
Model for tumour growth with treatment by continuous and pulsed chemotherapy
Peer reviewedPreprin
Dynamics of Coronal Bright Points as seen by Sun Watcher using Active Pixel System detector and Image Processing (SWAP), Atmospheric Imaging Assembly AIA), and Helioseismic and Magnetic Imager (HMI)
The \textit{Sun Watcher using Active Pixel system detector and Image
Processing}(SWAP) on board the \textit{PRoject for OnBoard Autonomy\todash 2}
(PROBA\todash 2) spacecraft provides images of the solar corona in EUV channel
centered at 174 \AA. These data, together with \textit{Atmospheric Imaging
Assembly} (AIA) and the \textit{Helioseismic and Magnetic Imager} (HMI) on
board \textit{Solar Dynamics Observatory} (SDO), are used to study the dynamics
of coronal bright points. The evolution of the magnetic polarities and
associated changes in morphology are studied using magnetograms and
multi-wavelength imaging. The morphology of the bright points seen in
low-resolution SWAP images and high-resolution AIA images show different
structures, whereas the intensity variations with time show similar trends in
both SWAP 174 and AIA 171 channels. We observe that bright points are seen in
EUV channels corresponding to a magnetic-flux of the order of Mx. We
find that there exists a good correlation between total emission from the
bright point in several UV\todash EUV channels and total unsigned photospheric
magnetic flux above certain thresholds. The bright points also show periodic
brightenings and we have attempted to find the oscillation periods in bright
points and their connection to magnetic flux changes. The observed periods are
generally long (10\todash 25 minutes) and there is an indication that the
intensity oscillations may be generated by repeated magnetic reconnection
Diffeomorphism Invariance in the Hamiltonian formulation of General Relativity
It is shown that when the Einstein-Hilbert Lagrangian is considered without
any non-covariant modifications or change of variables, its Hamiltonian
formulation leads to results consistent with principles of General Relativity.
The first-class constraints of such a Hamiltonian formulation, with the metric
tensor taken as a canonical variable, allow one to derive the generator of
gauge transformations, which directly leads to diffeomorphism invariance. The
given Hamiltonian formulation preserves general covariance of the
transformations derivable from it. This characteristic should be used as the
crucial consistency requirement that must be met by any Hamiltonian formulation
of General Relativity.Comment: 13 page
Logarithmic Corrections to Rotating Extremal Black Hole Entropy in Four and Five Dimensions
We compute logarithmic corrections to the entropy of rotating extremal black
holes using quantum entropy function i.e. Euclidean quantum gravity approach.
Our analysis includes five dimensional supersymmetric BMPV black holes in type
IIB string theory on T^5 and K3 x S^1 as well as in the five dimensional CHL
models, and also non-supersymmetric extremal Kerr black hole and slowly
rotating extremal Kerr-Newmann black holes in four dimensions. For BMPV black
holes our results are in perfect agreement with the microscopic results derived
from string theory. In particular we reproduce correctly the dependence of the
logarithmic corrections on the number of U(1) gauge fields in the theory, and
on the angular momentum carried by the black hole in different scaling limits.
We also explain the shortcomings of the Cardy limit in explaining the
logarithmic corrections in the limit in which the (super)gravity description of
these black holes becomes a valid approximation. For non-supersymmetric
extremal black holes, e.g. for the extremal Kerr black hole in four dimensions,
our result provides a stringent testing ground for any microscopic explanation
of the black hole entropy, e.g. Kerr/CFT correspondence.Comment: LaTeX file, 50 pages; v2: added extensive discussion on the relation
between boundary condition and choice of ensemble, modified analysis for
slowly rotating black holes, all results remain unchanged, typos corrected;
v3: minor additions and correction
Critical behavior in the variation of GDR width at low temperature
We present the first experimental giant dipole resonance (GDR) width
systematics, in the temperature region 0.8 1.2 MeV for Tl, a
near Pb nucleus, to investigate the evolution of the GDR width in shell effect
& pairing dominated region. The extracted GDR widths are well below the
predictions of shell effect corrected thermal shape fluctuation model (TSFM)
and thermal pairing included phonon damping model. A similar behavior of the
GDR width is also observed for Cu measured in the present work and
Sb, measured earlier. This discrepancy is attributed to the GDR induced
quadrupole moment leading to a critical point in the increase of the GDR width
with temperature. We incorporate this novel idea in the phenomenological
description based on the TSFM for a better understanding of the GDR width
systematics for the entire range of mass, spin and temperature.Comment: Accepted for publication in Phys. Lett. B, 7 pages, 4 figure
LAMBDA: Large Area Modular BaF2 Detector Array for the measurement of high energy gamma rays
A large BaF2 detector array along with its dedicated CAMAC electronics and
VME based data acquisition system has been designed, constructed and installed
successfully at VECC, Kolkata for studying high energy gamma rays (E>8 MeV).
The array consists of 162 detector elements. The detectors were fabricated from
bare barium fluoride crystals (each measuring 35 cm in length and having
cross-sectional area of 3.5 cm X 3.5 cm X 35.0 cm). The basic properties of the
detectors (energy resolution, time resolution, efficiency, uniformity, fast to
slow ratio etc.) were studied exhaustively. Complete GEANT3 monte carlo
simulations were performed to optimize the detector design and also to generate
the response function. The detector system has been used successfully to
measure high energy photons from 113Sb, formed by bombarding 145 and 160 MeV
20Ne beams on a 93Nb target. The measured experimental spectra are in good
agreement with those from a modified version of the statistical model code
CASCADE. In this paper, we present the complete description of this detector
array along with its in-beam performance.Comment: 18 pages, 14 figures, accepted in NIM
Le Chatelier-Braun principle in cosmological physics
Assuming that dark energy may be treated as a fluid with a well defined
temperature, close to equilibrium, we argue that if nowadays there is a
transfer of energy between dark energy and dark matter, it must be such that
the latter gains energy from the former and not the other way around.Comment: 6 pages, revtex file, no figures; version accepted for publication in
General Relativity and Gravitatio
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