207 research outputs found
Correlations across horizons in quantum cosmology
Different spacetime regions separated by horizons are not related to each
other. We know that this statement holds for classical spacetimes. In this
paper we carry out a canonical quantization of a Kantowski-Sachs minisuperspace
model whose classical solutions exhibit both an event horizon and a
cosmological horizon in order to check whether the above statement also holds
from the quantum gravitational point of view. Our analysis shows that in fact
this is not the case: Quantum gravitational states with support in spacetime
configurations that exclusively describe either the region between horizons or
outside them are not consistent in the sense that there exist unitary operators
describing a natural notion of evolution that connect them. In other words,
unitarity is only preserved in this quantization when dealing with the whole
spacetime and not in each region separately.Comment: 10 pages, 5 figure
Hierarchy and Wave Functions in a Simple Quantum Cosmology
Astrophysical observations indicate the expansion of the universe is
accelerating. Applying the holographic entropy conjecture to the cosmological
horizon in an accelerating universe suggests the universe has only a finite
number of degrees of freedom. This is consistent with a closed universe arising
from a quantum fluctuation, with zero total quantum numbers. If space-time has
eleven dimensions, and the universe began as a closed force-symmetric
ten-dimensional space with characteristic dimension L, seven of the space
dimensions must have collapsed to generate the three large space dimensions we
see. The holographic conjecture then suggests the initial length scale L must
be roughly twenty orders of magnitude larger than the Planck length.
Accordingly, the nuclear force must be roughly forty orders of magnitude
stronger than gravity, possibly resolving the force hierarchy problem. A
wavefunction for the radius of curvature of the universe can be obtained from
the Schrodinger equation derived by Elbaz and Novello. The product of this
wavefunction and its complex conjugate can be interpreted as the probability
density for finding a given radius of curvature in one of the infinity of
measurements of the radius of curvature possible (in principle) at any location
in a homogeneous isotropic universe.Comment: 4 pages, no figures, abstract corrected to insert omitted word
Intensification of UV-C tertiary treatment : Disinfection and removal of micropollutants by sulfate radical based Advanced Oxidation Processes
This study explores the enhancement of UV-C tertiary treatment by sulfate radical based Advanced Oxidation Processes (SR-AOPs), including photolytic activation of peroxymonosulfate (PMS) and persulfate (PS) and their photocatalytic activation using Fe(II). Their efficiency was assessed both for the inactivation of microorganisms and the removal or micropollutants (MPs) in real wastewater treatment plant effluents. Under the studied experimental range (UV-C dose 5.7-57 J/L; UV-C contact time 3 to 28 s), the photolysis of PMS and PS (0.01 mM) increased up to 25% the bacterial removal regarding to UV-C system. The photolytic activation of PMS led to the total inactivation of bacteria (approximate to 5.70 log) with the highest UV-C dose (57 J/L). However, these conditions were insufficient to remove the MPs, being required oxidant's dosages of 5 mM to remove above 90% of carbamazepine, diclofenac, atenolol and triclosan. The best efficiencies were achieved by the combination of PMS or PS with Fe(II), leading to the total removal of the MPs using a low UV-C dosage (19 J/L), UV-C contact time (9 s) and reagent's dosages (0.5 mM). Finally, high mineralization was reached ( > 50%) with photocatalytic activation of PMS and PS even with low reagent's dosages.Peer reviewe
High Throughput Screening for Inhibitors of Alpha-Galactosidase
Fabry disease is a rare X-linked lysosomal storage disorder caused by a deficiency in α-galactosidase A (GLA), which catalyzes the hydrolysis of terminal α-galactosyl groups from glycosphingolipids, such as globotriaosylceramide (Gb3). Many of the mutations in the GLA gene are missense alterations that cause misfolding, decreased stability, and/or mistrafficking of this protein. Small molecule compounds that correct the misfolding and mistrafficking, or activate the mutant enzyme, may be useful in the treatment of Fabry disease. We have screened a library of approximately 230,000 compounds using preparations of human recombinant protein and purified coffee bean enzyme in an effort to find activators and inhibitors of this enzyme. Lansoprazole was identified as a small molecule inhibitor of GLA derived from coffee beans (IC50 = 6.4 μM), but no inhibitors or activators were identified for the human enzyme. The screening results indicate that human GLA is a difficult target for small molecule inhibition or activation
The function of phosphatidylinositol 5-phosphate 4-kinase γ (PI5P4Kγ) explored using a specific inhibitor that targets the PI5P-binding site.
NIH-12848 (NCGC00012848-02), a putative phosphatidylinositol 5-phosphate 4-kinase γ (PI5P4Kγ) inhibitor, was explored as a tool for investigating this enigmatic, low activity, lipid kinase. PI5P4K assays in vitro showed that NIH-12848 inhibited PI5P4Kγ with an IC50 of approximately 1 μM but did not inhibit the α and β PI5P4K isoforms at concentrations up to 100 μM. A lack of inhibition of PI5P4Kγ ATPase activity suggested that NIH-12848 does not interact with the enzyme's ATP-binding site and direct exploration of binding using hydrogen-deuterium exchange (HDX)-MS (HDX-MS) revealed the putative PI5P-binding site of PI5P4Kγ to be the likely region of interaction. This was confirmed by a series of mutation experiments which led to the identification of a single PI5P4Kγ amino acid residue that can be mutated to its PI5P4Ks α and β homologue to render PI5P4Kγ resistant NIH-12848 inhibition. NIH-12848 (10 μM) was applied to cultured mouse principal kidney cortical collecting duct (mpkCCD) cells which, we show, express PI5P4Kγ that increases when the cells grow to confluence and polarize. NIH-12848 inhibited the translocation of Na⁺/K⁺-ATPase to the plasma membrane that occurs when mpkCCD cells grow to confluence and also prevented reversibly their forming of 'domes' on the culture dish. Both these NIH-12848-induced effects were mimicked by specific RNAi knockdown of PI5P4Kγ, but not that of PI5P4Ks α or β. Overall, the data reveal a probable contribution of PI5P4Kγ to the development and maintenance of epithelial cell functional polarity and show that NIH-12848 is a potentially powerful tool for exploring the cell physiology of PI5P4Ks.J.H.C was supported by the MRC (Grant RG64071), M-L.G. by the BBSRC (Grant RG65394), and J.H.B. by the BHF (Grant PG11/109/29247).This is the final version of the article. It first appeared from the Biochemical Society via http://dx.doi.org/10.1042/BJ2014133
Quantum Gravity and Inflation
Using the Ashtekar-Sen variables of loop quantum gravity, a new class of
exact solutions to the equations of quantum cosmology is found for gravity
coupled to a scalar field, that corresponds to inflating universes. The scalar
field, which has an arbitrary potential, is treated as a time variable,
reducing the hamiltonian constraint to a time-dependent Schroedinger equation.
When reduced to the homogeneous and isotropic case, this is solved exactly by a
set of solutions that extend the Kodama state, taking into account the time
dependence of the vacuum energy. Each quantum state corresponds to a classical
solution of the Hamiltonian-Jacobi equation. The study of the latter shows
evidence for an attractor, suggesting a universality in the phenomena of
inflation. Finally, wavepackets can be constructed by superposing solutions
with different ratios of kinetic to potential scalar field energy, resolving,
at least in this case, the issue of normalizability of the Kodama state.Comment: 18 Pages, 2 Figures; major corrections to equations but prior results
still hold, updated reference
On the Schroedinger Representation for a Scalar Field on Curved Spacetime
It is generally known that linear (free) field theories are one of the few
QFT that are exactly soluble. In the Schroedinger functional description of a
scalar field on flat Minkowski spacetime and for flat embeddings, it is known
that the usual Fock representation is described by a Gaussian measure. In this
paper, arbitrary globally hyperbolic space-times and embeddings of the Cauchy
surface are considered. The classical structures relevant for quantization are
used for constructing the Schroedinger representation in the general case. It
is shown that in this case, the measure is also Gaussian. Possible implications
for the program of canonical quantization of midisuperspace models are pointed
out.Comment: 11 pages, Revtex, no figure
The linearization of the Kodama state
We study the question of whether the linearization of the Kodama state around
classical deSitter spacetime is normalizable in the inner product of the theory
of linearized gravitons on deSitter spacetime. We find the answer is no in the
Lorentzian theory. However, in the Euclidean theory the corresponding
linearized Kodama state is delta-functional normalizable. We discuss whether
this result invalidates the conjecture that the full Kodama state is a good
physical state for quantum gravity with positive cosmological constant.Comment: 14 pages, statement on the corresponding Yang-Mills case correcte
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