38 research outputs found
A dark energy multiverse
We present cosmic solutions corresponding to universes filled with dark and
phantom energy, all having a negative cosmological constant. All such solutions
contain infinite singularities, successively and equally distributed along
time, which can be either big bang/crunchs or big rips singularities.
Classicaly these solutions can be regarded as associated with multiverse
scenarios, being those corresponding to phantom energy that may describe the
current accelerating universe
Classical and semi-classical energy conditions
The standard energy conditions of classical general relativity are (mostly)
linear in the stress-energy tensor, and have clear physical interpretations in
terms of geodesic focussing, but suffer the significant drawback that they are
often violated by semi-classical quantum effects. In contrast, it is possible
to develop non-standard energy conditions that are intrinsically non-linear in
the stress-energy tensor, and which exhibit much better well-controlled
behaviour when semi-classical quantum effects are introduced, at the cost of a
less direct applicability to geodesic focussing. In this article we will first
review the standard energy conditions and their various limitations. (Including
the connection to the Hawking--Ellis type I, II, III, and IV classification of
stress-energy tensors). We shall then turn to the averaged, nonlinear, and
semi-classical energy conditions, and see how much can be done once
semi-classical quantum effects are included.Comment: V1: 25 pages. Draft chapter, on which the related chapter of the book
"Wormholes, Warp Drives and Energy Conditions" (to be published by Springer),
will be based. V2: typos fixed. V3: small typo fixe
A graceful multiversal link of particle physics to cosmology
In this paper we work out a multiverse scenario whose physical
characteristics enable us to advance the following the conjecture that whereas
the physics of particles and fields is confined to live in the realm of the
whole multiverse formed by finite-time single universes, that for our
observable universe must be confined just in one of the infinite number of
universes of the multiverse when such a universe is consistently referred to an
infinite cosmic time. If this conjecture is adopted then some current
fundamental problems that appear when one tries to make compatible particle
physics and cosmology- such as that for the cosmological constant, the arrow of
time and the existence of a finite proper size of the event horizon- can be
solved.Comment: 10 pages, LaTe
Observers in an accelerated universe
If the current acceleration of our Universe is due to a cosmological
constant, then a Coleman-De Luccia bubble will nucleate in our Universe. In
this work, we consider that our observations could be likely in this framework,
consisting in two infinite spaces, if a foliation by constant mean curvature
hypersurfaces is taken to count the events in the spacetime. Thus, we obtain
and study a particular foliation, which covers the existence of most observers
in our part of spacetime.Comment: revised version, accepted in EPJ
Accretions of Various Types of Dark Energies onto Morris-Thorne Wormhole
In this work, we have studied accretion of the dark energies onto
Morris-Thorne wormhole. For quintessence like dark energy, the mass of the
wormhole decreases and phantom like dark energy, the mass of wormhole
increases. We have assumed two types of dark energy like variable modified
Chaplygin gas (VMCG) and generalized cosmic Chaplygin gas (GCCG). We have found
the expression of wormhole mass in both cases. We have found the mass of the
wormhole at late universe and this is finite. For our choices the parameters
and the function , these models generate only quintessence dark energy
(not phantom) and so wormhole mass decreases during evolution of the universe.
Next we have assumed 5 kinds of parametrizations of well known dark energy
models. These models generate both quintessence and phantom scenarios. So if
these dark energies accrete onto the wormhole, then for quintessence stage,
wormhole mass decreases upto a certain value (finite value) and then again
increases to infinite value for phantom stage during whole evolution of the
universe. We also shown these results graphically.Comment: 9 pages, 7 figures. arXiv admin note: text overlap with
arXiv:1112.615
SMARCA4 deficient tumours are vulnerable to KDM6A/UTX and KDM6B/JMJD3 blockade
The authors thank Isabel Bartolessis (Cancer Genetics Group) at IJC for technical assistance. This work was supported by the Spanish Ministry of Economy and CompetitivityMINECO (grant number SAF-2017-82186R, to M.S.-C., and grant PI19/01320 to A. Villanueva) and from the Fundacion Cientifica of the Asociacion Espanola Contra el Cancer (AECC) (grant number GCB14142170MONT) to M.S.-C. A. Villanueva is also funded by the Department of Health of the Generalitat de Catalunya (2014SGR364). O.A. R. received a Juan de la Cierva postdoctoral contract (grant No. IJCI-2016-28201, until November 2019) and an AECC research contract (INVES19045ROME from December 2019). A. Vilarrubi, P.L. and A.A. are supported by pre-doctoral contracts from the Spanish MINECO (FPI-fellowship: PRE2018-084624, BES-2015-072204 and FPU17/00067). M.S. was supported by a Rio Hortega contract from the Instituto de Salud Carlos III (CM17/00180). L.F. received a European Union Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie Actions grant agreement, number 799850.Despite the genetic inactivation of SMARCA4, a core component of the SWI/SNF-complex
commonly found in cancer, there are no therapies that effectively target SMARCA4-deficient
tumours. Here, we show that, unlike the cells with activated MYC oncogene, cells with
SMARCA4 inactivation are refractory to the histone deacetylase inhibitor, SAHA, leading to
the aberrant accumulation of H3K27me3. SMARCA4-mutant cells also show an impaired
transactivation and significantly reduced levels of the histone demethylases KDM6A/UTX
and KDM6B/JMJD3, and a strong dependency on these histone demethylases, so that its
inhibition compromises cell viability. Administering the KDM6 inhibitor GSK-J4 to mice
orthotopically implanted with SMARCA4-mutant lung cancer cells or primary small cell
carcinoma of the ovary, hypercalcaemic type (SCCOHT), had strong anti-tumour effects. In
this work we highlight the vulnerability of KDM6 inhibitors as a characteristic that could be
exploited for treating SMARCA4-mutant cancer patients.Spanish Ministry of Economy and Competitivity-MINECO SAF-2017-82186R
PI19/01320Fundacion Cientifica of the Asociacion Espanola Contra el Cancer (AECC) GCB14142170MONTDepartment of Health of the Generalitat de Catalunya 2014SGR364Juan de la Cierva postdoctoral contract IJCI-2016-28201AECC research contract INVES19045ROMESpanish MINECO PRE2018-084624
BES-2015-072204
FPU17/00067Instituto de Salud Carlos III
European Commission CM17/00180European Union Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie Actions grant agreement 79985
Follow-Up Study Confirms the Presence of Gastric Cancer DNA Methylation Hallmarks in High-Risk Precursor Lesions
Intestinal metaplasia confers an increased risk of progression to gastric cancer. However, some intestinal metaplasia patients do not develop cancer. The development of robust molecular biomarkers to stratify patients with advanced gastric precursor lesions at risk of cancer progression will contribute to guiding programs for prevention. Starting from a genome-wide methylation study, we have simplified the detection method regarding candidate-methylation tests to improve their applicability in the clinical environment. We identified CpG methylation at the ZNF793 and RPRM promoters as a common event in intestinal metaplasia and intestinal forms of gastric cancer. Furthermore, we also showed that Helicobacter pylori infection influences DNA methylation in early precursor lesions but not in intestinal metaplasia, suggesting that therapeutic strategies to prevent epigenome reprogramming toward a cancer signature need to be adopted early in the precursor cascade. To adopt prevention strategies in gastric cancer, it is imperative to develop robust biomarkers with acceptable costs and feasibility in clinical practice to stratified populations according to risk scores. With this aim, we applied an unbiased genome-wide CpG methylation approach to a discovery cohort composed of gastric cancer (n = 24), and non-malignant precursor lesions (n = 64). Then, candidate-methylation approaches were performed in a validation cohort of precursor lesions obtained from an observational longitudinal study (n = 264), with a 12-year follow-up to identify repression or progression cases. H. pylori stratification and histology were considered to determine their influence on the methylation dynamics. As a result, we ascertained that intestinal metaplasia partially recapitulates patterns of aberrant methylation of intestinal type of gastric cancer, independently of the H. pylori status. Two epigenetically regulated genes in cancer, RPRM and ZNF793, consistently showed increased methylation in intestinal metaplasia with respect to earlier precursor lesions. In summary, our result supports the need to investigate the practical utilities of the quantification of DNA methylation in candidate genes as a marker for disease progression. In addition, the H. pylori-dependent methylation in intestinal metaplasia suggests that pharmacological treatments aimed at H. pylori eradication in the late stages of precursor lesions do not prevent epigenome reprogramming toward a cancer signature
Quantum gravity phenomenology at the dawn of the multi-messenger era—A review
The exploration of the universe has recently entered a new era thanks to the multi-messenger paradigm, characterized by a continuous increase in the quantity and quality of experimental data that is obtained by the detection of the various cosmic messengers (photons, neutrinos, cosmic rays and gravitational waves) from numerous origins. They give us information about their sources in the universe and the properties of the intergalactic medium. Moreover, multi-messenger astronomy opens up the possibility to search for phenomenological signatures of quantum gravity. On the one hand, the most energetic events allow us to test our physical theories at energy regimes which are not directly accessible in accelerators; on the other hand, tiny effects in the propagation of very high energy particles could be amplified by cosmological distances. After decades of merely theoretical investigations, the possibility of obtaining phenomenological indications of Planck-scale effects is a revolutionary step in the quest for a quantum theory of gravity, but it requires cooperation between different communities of physicists (both theoretical and experimental). This review, prepared within the COST Action CA18108 “Quantum gravity phenomenology in the multi-messenger approach”, is aimed at promoting this cooperation by giving a state-of-the art account of the interdisciplinary expertise that is needed in the effective search of quantum gravity footprints in the production, propagation and detection of cosmic messengers.publishedVersio
Quantum gravity phenomenology at the dawn of the multi-messenger era -- A review
The exploration of the universe has recently entered a new era thanks to the
multi-messenger paradigm, characterized by a continuous increase in the
quantity and quality of experimental data that is obtained by the detection of
the various cosmic messengers (photons, neutrinos, cosmic rays and
gravitational waves) from numerous origins. They give us information about
their sources in the universe and the properties of the intergalactic medium.
Moreover, multi-messenger astronomy opens up the possibility to search for
phenomenological signatures of quantum gravity. On the one hand, the most
energetic events allow us to test our physical theories at energy regimes which
are not directly accessible in accelerators; on the other hand, tiny effects in
the propagation of very high energy particles could be amplified by
cosmological distances. After decades of merely theoretical investigations, the
possibility of obtaining phenomenological indications of Planck-scale effects
is a revolutionary step in the quest for a quantum theory of gravity, but it
requires cooperation between different communities of physicists (both
theoretical and experimental). This review is aimed at promoting this
cooperation by giving a state-of-the art account of the interdisciplinary
expertise that is needed in the effective search of quantum gravity footprints
in the production, propagation and detection of cosmic messengers