17,844 research outputs found
Conformal Gravity with Electrodynamics for Fermion Fields and their Symmetry Breaking Mechanism
In this paper we consider an axial torsion to build metric-compatible
connections in conformal gravity, with gauge potentials; the geometric
background is filled with Dirac spinors: scalar fields with suitable potentials
are added eventually. The system of field equations is worked out to have
torsional effects converted into spinorial self-interactions: the massless
spinors display self-interactions of a specific form that gives them the
features they have in the non-conformal theory but with the additional
character of renormalizability, and the mechanisms of generation of mass and
cosmological constants become dynamical. As a final step we will address the
cosmological constant and coincidence problems.Comment: 13 page
Spontaneous breaking of conformal invariance in theories of conformally coupled matter and Weyl gravity
We study the theory of Weyl conformal gravity with matter degrees of freedom
in a conformally invariant interaction. Specifically, we consider a triplet of
scalar fields and SO(3) non-abelian gauge fields, i.e. the Georgi-Glashow model
conformally coupled to Weyl gravity. We show that the equations of motion admit
solutions spontaneously breaking the conformal symmetry and the gauge symmetry,
providing a mechanism for supplying a scale in the theory. The vacuum solution
corresponds to anti-de-Sitter space-time, while localized soliton solutions
correspond to magnetic monopoles in asymptotically anti-de-Sitter space-time.
The resulting effective action gives rise to Einstein gravity and the residual
U(1) gauge theory. This mechanism strengthens the reasons for considering
conformally invariant matter-gravity theory, which has shown promising
indications concerning the problem of missing matter in galactic rotation
curves.Comment: 20 pages, 1 figure, revised and added reference
Quantum effects in Acoustic Black Holes: the Backreaction
We investigate the backreaction equations for an acoustic black hole formed
in a Laval nozzle under the assumption that the motion of the fluid is
one-dimensional. The solution in the near-horizon region shows that as phonons
are (thermally) radiated the sonic horizon shrinks and the temperature
decreases. This contrasts with the behaviour of Schwarzschild black holes, and
is similar to what happens in the evaporation of (near-extremal)
Reissner-Nordstrom black holes (i.e. infinite evaporation time). Finally, by
appropriate boundary conditions the solution is extended in both the asymptotic
regions of the nozzle.Comment: 23 pages, latex, 1 figure; revised version, to appear in Phys. Rev.
Overexpression of ultraconserved region 83-induces lung cancer tumorigenesis
The expression of non–coding RNAs (ncRNAs) is dysregulated in human cancers. The transcribed ultraconserved regions (T-UCRs) express long ncRNAs involved in human carcinogenesis. T-UCRs are non-coding genomic sequence that are 100% conserved across humans, rats and mice. Conservation of genomic sequences across species intrinsically implies an essential functional role and so we considered the expression of T-UCRs in lung cancer. Using a custom microarray we analyzed the global expression of T-UCRs. Among these T-UCRs, the greatest variation was observed for antisense ultraconserved element 83 (uc.83-), which was upregulated in human lung cancer tissues compared with adjacent non cancerous tissues. Even though uc.83- is located within the long intergenic non-protein coding RNA 1876 (LINC01876) gene, we found that the transcribed uc.83- is expressed independently of LINC01876 and was cloned as a 1143-bp RNA gene. In this study, functional analysis confirmed important effects of uc.83- on genes involved in cell growth of human cells. siRNA against uc.83- decreased the growth of lung cancer cells while the upregulation through a vector overexpressing the uc.83- RNA increased cell proliferation. We also show the oncogenic function of uc.83- is mediated by the phosphorylation of AKT and ERK 1/2, two important biomarkers of lung cancer cell proliferation. Based on our findings, inhibition against uc.83- could be a future therapeutic treatment for NSCLC to achieve simultaneous blockade of pathways involved in lung carcinogenesis
Multi-band spectroscopy of inhomogeneous Mott-insulator states of ultracold bosons
In this work, we use inelastic scattering of light to study the response of
inhomogeneous Mott-insulator gases to external excitations. The experimental
setup and procedure to probe the atomic Mott states are presented in detail. We
discuss the link between the energy absorbed by the gases and accessible
experimental parameters as well as the linearity of the response to the
scattering of light. We investigate the excitations of the system in multiple
energy bands and a band-mapping technique allows us to identify band and
momentum of the excited atoms. In addition the momentum distribution in the
Mott states which is spread over the entire first Brillouin zone enables us to
reconstruct the dispersion relation in the high energy bands using a single
Bragg excitation with a fixed momentum transfer.Comment: 19 pages, 7 figure
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