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Author |
Araujo Filho, A.A. |
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Title |
Thermodynamics of massless particles in curved spacetime |
Type |
Journal Article |
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Year |
2023 |
Publication |
International Journal of Geometric Methods in Modern Physics |
Abbreviated Journal |
Int. J. Geom. Methods Mod. Phys. |
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Volume |
12 |
Issue |
13 |
Pages |
2350226 - 40pp |
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Keywords |
Einstein-aether; thermodynamic properties; curved spacetime |
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Abstract |
This work is devoted to study the behavior of massless particles within the context of curved spacetime. In essence, we investigate the consequences of the scale factor C(?) of the Friedmann-Robertson-Walker metric in the Einstein-aether formalism to study photon-like particles. To do so, we consider the system within the canonical ensemble formalism in order to derive the following thermodynamic state quantities: spectral radiance, Helmholtz free energy, pressure, entropy, mean energy and the heat capacity. Moreover, the correction to the Stefan-Boltzmann law and the equation of states are also provided. Particularly, we separate our study within three distinct cases, i.e. s = 0, p = 0; s = 1, p = 1; s = 2, p = 1. In the first one, the results are derived numerically. Nevertheless, for the rest of the cases, all the calculations are accomplished analytically showing explicitly the dependence of the scale factor C(?) and the Riemann zeta function ?(s). Furthermore, our analyses are accomplished in general taking into account three different regimes of temperature of the universe, i.e. the inflationary era (T = 10(13)GeV), the electroweak epoch (T = 10(3)GeV) and the cosmic microwave background (T = 10(-13)GeV). |
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Address |
[Araujo Filho, A. A.] Univ Fed Cearra UFC, Dept Fis, Campus Pici,CP 6030, BR-60455760 Fortaleza, CE, Brazil, Email: dilto@fisica.ufc.br |
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Publisher |
World Scientific Publ Co Pte Ltd |
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Language |
English |
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ISSN  |
0219-8878 |
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Notes |
WOS:001048378900001 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
5613 |
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Author |
Di Valentino, E.; Mena, O.; Pan, S.; Visinelli, L.; Yang, W.Q.; Melchiorri, A.; Mota, D.F.; Riess, A.G.; Silk, J. |
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Title |
In the realm of the Hubble tension – a review of solutions |
Type |
Journal Article |
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Year |
2021 |
Publication |
Classical and Quantum Gravity |
Abbreviated Journal |
Class. Quantum Gravity |
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Volume |
38 |
Issue |
15 |
Pages |
153001 - 110pp |
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Keywords |
cosmological parameters; cosmology; dark energy; Hubble constant |
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Abstract |
The simplest ΛCDM model provides a good fit to a large span of cosmological data but harbors large areas of phenomenology and ignorance. With the improvement of the number and the accuracy of observations, discrepancies among key cosmological parameters of the model have emerged. The most statistically significant tension is the 4 sigma to 6 sigma disagreement between predictions of the Hubble constant, H (0), made by the early time probes in concert with the 'vanilla' ΛCDM cosmological model, and a number of late time, model-independent determinations of H (0) from local measurements of distances and redshifts. The high precision and consistency of the data at both ends present strong challenges to the possible solution space and demands a hypothesis with enough rigor to explain multiple observations-whether these invoke new physics, unexpected large-scale structures or multiple, unrelated errors. A thorough review of the problem including a discussion of recent Hubble constant estimates and a summary of the proposed theoretical solutions is presented here. We include more than 1000 references, indicating that the interest in this area has grown considerably just during the last few years. We classify the many proposals to resolve the tension in these categories: early dark energy, late dark energy, dark energy models with 6 degrees of freedom and their extensions, models with extra relativistic degrees of freedom, models with extra interactions, unified cosmologies, modified gravity, inflationary models, modified recombination history, physics of the critical phenomena, and alternative proposals. Some are formally successful, improving the fit to the data in light of their additional degrees of freedom, restoring agreement within 1-2 sigma between Planck 2018, using the cosmic microwave background power spectra data, baryon acoustic oscillations, Pantheon SN data, and R20, the latest SH0ES Team Riess, et al (2021 Astrophys. J. 908 L6) measurement of the Hubble constant (H (0) = 73.2 +/- 1.3 km s(-1) Mpc(-1) at 68% confidence level). However, there are many more unsuccessful models which leave the discrepancy well above the 3 sigma disagreement level. In many cases, reduced tension comes not simply from a change in the value of H (0) but also due to an increase in its uncertainty due to degeneracy with additional physics, complicating the picture and pointing to the need for additional probes. While no specific proposal makes a strong case for being highly likely or far better than all others, solutions involving early or dynamical dark energy, neutrino interactions, interacting cosmologies, primordial magnetic fields, and modified gravity provide the best options until a better alternative comes along. |
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Address |
[Di Valentino, Eleonora] Univ Durham, Inst Particle Phys Phenomenol, Dept Phys, Durham DH1 3LE, England, Email: eleonora.di-valentino@durham.ac.uk |
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Publisher |
Iop Publishing Ltd |
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English |
Summary Language |
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Original Title |
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Abbreviated Series Title |
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Series Volume |
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ISSN |
0264-9381 |
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Notes |
WOS:000672148200001 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
4931 |
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Author |
Araujo Filho, A.A.; Furtado, J.; Reis, J.A.A.S.; Silva, J.E.G. |
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Title |
Thermodynamical properties of an ideal gas in a traversable wormhole |
Type |
Journal Article |
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Year |
2023 |
Publication |
Classical and Quantum Gravity |
Abbreviated Journal |
Class. Quantum Gravity |
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Volume |
40 |
Issue |
24 |
Pages |
245001 - 20pp |
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Keywords |
wormhole; thermodynamic properties; Ellis wormhole |
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Abstract |
In this work, we analyze the thermodynamic properties of non-interacting particles under influence of the gravitational field of a traversable wormhole. In particular, we investigate how the thermodynamic quantities are affected by the Ellis wormhole geometry, considering three different regions to our study: asymptotically far, close to the throat, and at the throat. The thermodynamic quantities turn out to depend strongly on parameter that controls the wormhole throat radius. By varying it, there exist an expressive modification in the thermodynamic state quantities, exhibiting both usual matter and dark energy-like behaviors. Finally, the interactions are regarded to the energy density and it seems to indicate that it “cures” the dark energy-like features. |
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Address |
[Araujo Filho, A. A.] Univ Valencia, Dept Fis Teor, Burjassot 46100, Valencia, Spain, Email: dilto@fisica.ufc.br |
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Publisher |
IOP Publishing Ltd |
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Language |
English |
Summary Language |
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Original Title |
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Series Issue |
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ISSN |
0264-9381 |
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Conference |
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Notes |
WOS:001098744300001 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
5792 |
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Author |
Albiol, F.; Corbi, A.; Albiol, A. |
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Title |
Geometrical Calibration of X-Ray Imaging With RGB Cameras for 3D Reconstruction |
Type |
Journal Article |
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Year |
2016 |
Publication |
IEEE Transactions on Medical Imaging |
Abbreviated Journal |
IEEE Trans. Med. Imaging |
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Volume |
35 |
Issue |
8 |
Pages |
1952-1961 |
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Keywords |
3D reconstruction; camera system; geometric calibration; visible fiducials; X-ray imaging |
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Abstract |
We present a methodology to recover the geometrical calibration of conventional X-ray settings with the help of an ordinary video camera and visible fiducials that are present in the scene. After calibration, equivalent points of interest can be easily identifiable with the help of the epipolar geometry. The same procedure also allows the measurement of real anatomic lengths and angles and obtains accurate 3D locations from image points. Our approach completely eliminates the need for X-ray-opaque reference marks (and necessary supporting frames) which can sometimes be invasive for the patient, occlude the radiographic picture, and end up projected outside the imaging sensor area in oblique protocols. Two possible frameworks are envisioned: a spatially shifting X-ray anode around the patient/object and a moving patient that moves/rotates while the imaging system remains fixed. As a proof of concept, experiences with a device under test (DUT), an anthropomorphic phantom and a real brachytherapy session have been carried out. The results show that it is possible to identify common points with a proper level of accuracy and retrieve three-dimensional locations, lengths and shapes with a millimetric level of precision. The presented approach is simple and compatible with both current and legacy widespread diagnostic X-ray imaging deployments and it can represent a good and inexpensive alternative to other radiological modalities like CT. |
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Address |
[Albiol, Francisco; Corbi, Alberto] Univ Valencia, Consejo Super Invest Cient, Inst Fis Corpuscular IFIC, Paterna 46980, Spain, Email: kiko@ific.uv.es; |
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Publisher |
Ieee-Inst Electrical Electronics Engineers Inc |
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Language |
English |
Summary Language |
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Original Title |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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ISSN |
0278-0062 |
ISBN |
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Notes |
WOS:000381436000016 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
no |
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Call Number |
IFIC @ pastor @ |
Serial |
2781 |
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Author |
Lloret, E.; Fernandez, A.; Trbojevich, R.; Arnau, J.; Picouet, P.A. |
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Title |
Relevance of nanocomposite packaging on the stability of vacuum-packed dry cured ham |
Type |
Journal Article |
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Year |
2016 |
Publication |
Meat Science |
Abbreviated Journal |
Meat Sci. |
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Volume |
118 |
Issue |
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Pages |
8-14 |
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Keywords |
Clay; Nanocomposite; Polyamide; Skin; TBARS; Vacuum; Meat; Ham |
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Abstract |
In this study effects of a novel high barrier multilayer polyamide film containing dispersed nanoclays (PAN) on the stability of vacuum packed dry-cured ham were investigated during 90 days refrigerated storage in comparison with non-modified multilayer polyamide (PA) and a commercial high barrier film. Characteristic bands of the mineral in FT-IR spectra confirmed the presence of nanoclays in PAN, enhancing oxygen transmission barrier properties and UV protection. Packaging in PAN films did not originate significant changes on colour or lipid oxidation during prolonged storage of vacuum-packed dry-cured ham. Larger oxygen transmission rates in PA films caused changes in CIE b* during refrigerated storage. Ham quality was not affected by light exposition during 90 days and only curing had a significant benefit on colour and TBARS, being cured samples more stable during storage in all the packages used. Packaging of dry-cured ham in PAN was equivalent to commercial high barrier films. |
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Address |
[Lloret, Elsa; Arnau, Jacint; Picouet, Pierre A.] IRTA, Dept Tecnol Aliments, Monells, Girona, Spain, Email: pierre.picouet@irta.cat |
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Publisher |
Elsevier Sci Ltd |
Place of Publication |
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Editor |
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Language |
English |
Summary Language |
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Original Title |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
0309-1740 |
ISBN |
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Notes |
WOS:000380581100002 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
2774 |
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