Limits on the time variation of the Fermi constant<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>G</mml:mi><mml:mi>F</mml:mi></mml:msub></mml:math>based on type Ia supernova observations

Ferrero, Alejandro; Altschul, Brett

doi:10.1103/physrevd.82.123002

Cited by 10 publications

(8 citation statements)

References 22 publications

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“…Important results obtained by cluster dynamical mean-field methods have included the demonstration that in an appropriate doping and interaction range the two-dimensional Hubbard model can exhibit a pseudogap, 30,31 "Fermi arcs", [32][33][34][35][36] and a variation in electronic properties around the Fermi surface ("nodalantinodal differentiation"). [31][32][33][37][38][39] The methods have been shown to yield a multistage approach to the Mott transition with the insulating phase being separated from the weakly correlated metallic phase by a "sectorselective" phase where some regions of the Brillouin zone are gapped and others are not 37,38,40,41 and a number of physical properties were shown to be in good agreement with experiment. 38,39,42 Despite these successes, uncertainties remain.…”

Section: Introductionmentioning

confidence: 99%

Momentum-space anisotropy and pseudogaps: A comparative cluster dynamical mean-field analysis of the doping-driven metal-insulator transition in the two-dimensional Hubbard model

Gull¹,

Ferrero²,

Parcollet³

et al. 2010

Phys. Rev. B

177

198

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Cluster dynamical mean-field calculations based on 2-, 4-, 8-and 16-site clusters are used to analyze the doping-driven metal-insulator transition in the two-dimensional Hubbard model. Comparison of results obtained on different clusters enables a determination of those aspects of the physics that are common to all clusters and permits identification of artifacts associated with particular cluster geometries. A modest particle-hole asymmetry in the underlying band structure is shown to lead to qualitatively different behavior on the hole-doped side than on the electron-doped side. For particle-hole asymmetry of the sign and magnitude appropriate to high-Tc cuprates, the approach to the insulator from the hole-doping side is found to proceed in two stages from a high-doping region where the properties are those of a Fermi liquid with moderately renormalized parameters and very weak momentum dependence. As doping is reduced the system first enters an intermediate doping regime where the Fermi-liquid renormalizations are larger and the electron self-energy varies significantly around the Fermi surface and then passes to a small doping regime characterized by a gap on some parts of the Fermi surface but gapless behavior in other parts. On the electron-doped side the partially gapped regime does not occur, and the momentum dependence of the electron self-energy is less pronounced. Implications for the high-Tc cuprates and for the use of cluster dynamical mean-field methods in wider classes of problems are discussed.

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Section: Introductionmentioning

confidence: 99%

Momentum-space anisotropy and pseudogaps: A comparative cluster dynamical mean-field analysis of the doping-driven metal-insulator transition in the two-dimensional Hubbard model

Gull¹,

Ferrero²,

Parcollet³

et al. 2010

Phys. Rev. B

177

198

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“…While precise details of the explosion itself remain to be understood, the fading luminosity of a supernova days to months after the explosion is governed by beta decays of 56 Ni and 56 Co, as it has been confirmed in 2014 by direct observations [3,4]. This fact has been used [5,6] to constrain spacetime variations of the decay rates, which are determined by the Fermi constant G F . In the Standard Model, this "constant" is directly related to the vacuum expectation value v of the Brout-Englert-Higgs scalar field.…”

Section: Introductionmentioning

confidence: 96%

“…The relation between the amount of decaying isotopes and the supernova luminosity is not direct and we refer the reader to previous studies [5,6] for discussions of this point.…”

Section: Introductionmentioning

confidence: 99%

Constraining spacetime variations of nuclear decay rates from light curves of type Ia supernovae

et al. 2015

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The luminosity of fading type Ia supernovae is governed by radioactive decays of 56 Ni and 56 Co.The decay rates are proportional to the Fermi coupling constant G F and, therefore, are determined by the vacuum expectation value v of the Brout-Englert-Higgs field. We use publicly available sets of lightcurves of type Ia supernova at various redshifts to constrain possible spacetime variations of the 56 Ni decay rate. The resulting constraint is not very tight; however, it is the only direct bound on the variation of the decay rate for redshifts up to z ∼ 1. We discuss potential applications of the result to searches for non-constancy of G F and v.

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“…25.Jb The mechanism of interlayer (c-axis) transport in cuprate high temperature superconductors remains an actively debated subject. A qualitative difference between metallic in-plane and non-metallic out-of-plane resistivities [1] is a strong indication for predominantly incoherent nature of c-axis transport, which is achieved by interlayer hopping or tunneling [2][3][4][5][6][7]. The tunneling nature of c-axis transport leads to appearance of the intrinsic Josephson effect between CuO 2 planes in layered Bi 2 Sr 2 CaCu 2 O 8+δ (Bi-2212) cuprates at temperatures below T c [8].…”

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confidence: 99%

Observation of a subharmonic gap singularity in interlayer tunneling characteristics ofBi2Sr2CaCu2O8+δ

Krasnov

2016

Phys. Rev. B

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A subharmonic structure in Josephson junctions appears due to Andreev reflections within the junction. Here we report on experimental observation of a subharmonic half-gap singularity in interlayer tunneling characteristics of a layered high temperature superconductor Bi2Sr2CaCu2O 8+δ . The singularity is most pronounced in optimally doped crystals and vanishes with decreasing doping. It indicates existence of non-vanishing electronic density of states and certain metallic properties in the intermediate BiO layers, which grows stronger with increasing doping. This provides an additional coherent interlayer transport channel and can explain a gradual transition from an incoherent quasi-two-dimensional c-axis transport in underdoped to a coherent metallic transport in overdoped cuprates. Furthermore, due to a very small sub-gap current, the singularity allows unambiguous extraction of the superconducting gap, without distortion by self-heating. The mechanism of interlayer (c-axis) transport in cuprate high temperature superconductors remains an actively debated subject. A qualitative difference between metallic in-plane and non-metallic out-of-plane resistivities [1] is a strong indication for predominantly incoherent nature of c-axis transport, which is achieved by interlayer hopping or tunneling [2][3][4][5][6][7]. The tunneling nature of c-axis transport leads to appearance of the intrinsic Josephson effect between CuO 2 planes in layered Bi 2 Sr 2 CaCu 2 O 8+δ (Bi-2212) cuprates at temperatures below T c [8]. However, the electronic system in cuprates is not strictly two-dimensional. This has been demonstrated by observation of bonding-antibonding bilayer splitting of electronic bands [9]. Indications for coherent transport were obtained in strong magnetic fields [10]. Since the two dimensional superconductivity is suppressed by fluctuations [11], presence or absence of the coherent metallic transport in the c-axis direction, i.e., in the third dimension, and the mechanism of interlayer coupling remain to be important issues for understanding high temperature superconductivity.The intrinsic Josephson effect provides an accurate way of probing weak interlayer coupling in cuprates. Due to a d-wave symmetry of the order parameter, the product of the Josephson critical current I c and the normal resistance R n in intrinsic junctions should strongly depend on the coherence (momentum conservation) upon tunneling. The I c R n is maximum ∼ ∆/e for coherent, and zero for completely incoherent tunneling [12]. Here ∆ is the maximum value of the superconducting energy gap. Analysis of I c R n in intrinsic Josephson junctions indicated that in overdoped Bi-2212 interlayer tunneling is predominantly coherent I c R n ∼ ∆/e [13,14]. However, eI c R n /∆ rapidly decreases upon opening of the pseudogap in the underdoped state [13,14]. This may either * Electronic address: Vladimir.Krasnov@fysik.su.se indicate that interlayer tunneling becomes progressively more incoherent with decreasing doping [13], or that the Fermi surface i...

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Limits on the time variation of the Fermi constantGFbased on type Ia supernova observations

Abstract: The light curve of a type Ia supernova decays at a rate set by the β-decay lifetimes of the 56 Ni and 56 Co produced in the explosion. This makes such a light curve sensitive

Cited by 10 publications

References 22 publications

Momentum-space anisotropy and pseudogaps: A comparative cluster dynamical mean-field analysis of the doping-driven metal-insulator transition in the two-dimensional Hubbard model

Momentum-space anisotropy and pseudogaps: A comparative cluster dynamical mean-field analysis of the doping-driven metal-insulator transition in the two-dimensional Hubbard model

Constraining spacetime variations of nuclear decay rates from light curves of type Ia supernovae

Observation of a subharmonic gap singularity in interlayer tunneling characteristics ofBi2Sr2CaCu2O8+δ

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