Strong and weak gravity: A class of generally covariant mixing models of spin-2 neutral fields: Linearization

1975 ◽  
Vol 25 (2) ◽  
pp. 757-785 ◽  
Author(s):  
W. C. Hammel
Keyword(s):  
Mixing Models ◽  
Generally Covariant ◽  
Weak Gravity

scholarly journals Nonlinear Mixing Characteristics of Reflectance Spectra of Typical Mineral Pigments

Minerals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 626
Author(s):  
Shuqiang Lyu ◽  
Die Meng ◽  
Miaole Hou ◽  
Shuai Tian ◽  
Chunhao Huang ◽  
...  
Keyword(s):  
Nonlinear Model ◽  
Experimental Approach ◽  
Spectral Characteristics ◽  
Chinese Painting ◽  
Mixing Models ◽  
Nonlinear Mixing ◽  
Shortwave Infrared ◽  
Fully Constrained Least Squares ◽  
Spectral Mixing ◽  
Continuum Removal

Hyperspectral technology has been used to identify pigments that adhere to the surfaces of polychrome artifacts. However, the colors are often produced by the mixing of pigments, which requires that the spectral characteristics of the pigment mixtures be considered before pigment unmixing is conducted. Therefore, we proposed an experimental approach to investigate the nonlinear degree of spectral reflectance, using several mixing models, and to evaluate their performances in the study of typical mineral pigments. First, five mineral pigments of azurite, malachite, cinnabar, orpiment, and calcite were selected to form five groups of samples, according to their different mass ratios. Second, a fully constrained least squares algorithm based on the linear model and three algorithms based on the nonlinear model were employed to calculate the proportion of each pigment in the mixtures. We evaluated the abundance accuracy as well as the similarity between the measured and reconstructed spectra produced by those mixing models. Third, we conducted pigment unmixing on a Chinese painting to verify the applicability of the nonlinear model. Fourth, continuum removal was also introduced to test the nonlinearity of mineral pigment mixing. Finally, the results indicated that the spectral mixing of different mineral pigments was more in line with the nonlinear mixing model. The spectral nonlinearity of mixed pigments was higher near to the wavelength corresponding to their colors. Meanwhile, the nonlinearity increased with the wavelength increases in the shortwave infrared bands.

End Member and Bayesian mixing models consistently indicate near‐surface flowpath dominance in a pristine humid tropical rainforest

2021 ◽  
Author(s):  
Christian Birkel ◽  
Alicia Correa Barahona ◽  
Clément Duvert ◽  
Sebastián Granados Bolaños ◽  
Andres Chavarría Palma ◽  
...  
Keyword(s):  
Tropical Rainforest ◽  
Mixing Models ◽  
Near Surface ◽  
Bayesian Mixing Models

scholarly journals Weak gravity bounds in asymptotic string compactifications

2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
Brice Bastian ◽  
Thomas W. Grimm ◽  
Damian van de Heisteeg
Keyword(s):  
Black Holes ◽  
Moduli Space ◽  
Mass Formula ◽  
Complex Structure ◽  
Mass Ratio ◽  
De Sitter ◽  
String Compactifications ◽  
Type Iib String Theory ◽  
Bps States ◽  
Weak Gravity

Abstract We study the charge-to-mass ratios of BPS states in four-dimensional $$ \mathcal{N} $$ N = 2 supergravities arising from Calabi-Yau threefold compactifications of Type IIB string theory. We present a formula for the asymptotic charge-to-mass ratio valid for all limits in complex structure moduli space. This is achieved by using the sl(2)-structure that emerges in any such limit as described by asymptotic Hodge theory. The asymptotic charge-to-mass formula applies for sl(2)-elementary states that couple to the graviphoton asymptotically. Using this formula, we determine the radii of the ellipsoid that forms the extremality region of electric BPS black holes, which provides us with a general asymptotic bound on the charge-to-mass ratio for these theories. Finally, we comment on how these bounds for the Weak Gravity Conjecture relate to their counterparts in the asymptotic de Sitter Conjecture and Swampland Distance Conjecture.

scholarly journals The UV fate of anomalous U(1)s and the Swampland

2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
Nathaniel Craig ◽  
Isabel Garcia Garcia ◽  
Graham D. Kribs
Keyword(s):  
Quantum Gravity ◽  
Gauge Theories ◽  
Critical Size ◽  
Gauge Coupling ◽  
Low Energy ◽  
Gravitational Anomaly ◽  
Light Vector ◽  
Energy Theory ◽  
The Cost ◽  
Weak Gravity

Abstract Massive U(1) gauge theories featuring parametrically light vectors are suspected to belong in the Swampland of consistent EFTs that cannot be embedded into a theory of quantum gravity. We study four-dimensional, chiral U(1) gauge theories that appear anomalous over a range of energies up to the scale of anomaly-cancelling massive chiral fermions. We show that such theories must be UV-completed at a finite cutoff below which a radial mode must appear, and cannot be decoupled — a Stückelberg limit does not exist. When the infrared fermion spectrum contains a mixed U(1)-gravitational anomaly, this class of theories provides a toy model of a boundary into the Swampland, for sufficiently small values of the vector mass. In this context, we show that the limit of a parametrically light vector comes at the cost of a quantum gravity scale that lies parametrically below MP1, and our result provides field theoretic evidence for the existence of a Swampland of EFTs that is disconnected from the subset of theories compatible with a gravitational UV-completion. Moreover, when the low energy theory also contains a U(1)3 anomaly, the Weak Gravity Conjecture scale makes an appearance in the form of a quantum gravity cutoff for values of the gauge coupling above a certain critical size.

scholarly journals Supersymmetric SU(5)×U(1)χ and the weak gravity conjecture

2019 ◽  
Vol 100 (4) ◽  
Author(s):  
Abhishek Pal ◽  
Qaisar Shafi
Keyword(s):  
Weak Gravity

A revised model for lipid-normalizing δ13C values from aquatic organisms, with implications for isotope mixing models

2006 ◽  
Vol 43 (6) ◽  
pp. 1213-1222 ◽  
Author(s):  
MIKKO KILJUNEN ◽  
JONATHAN GREY ◽  
TUULA SINISALO ◽  
CHRIS HARROD ◽  
HEMMO IMMONEN ◽  
...  
Keyword(s):  
Aquatic Organisms ◽  
Mixing Models ◽  
Δ13c Values ◽  
Isotope Mixing Models

Soluble Two-Dimensional Models of Generally Covariant Field Theories

1973 ◽  
Vol 7 (8) ◽  
pp. 2309-2310
Author(s):  
Joseph Klarfeld ◽  
Alexander L. Harvey
Keyword(s):  
Field Theories ◽  
Two Dimensional ◽  
Dimensional Models ◽  
Generally Covariant ◽  
Covariant Field
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