Two-point correlation function of density perturbations in a large void universe

Nishikawa, Ryusuke; Yoo, Chul-Moon; Nakao, Ken–ichi

doi:10.1103/physrevd.88.123520

Cited by 7 publications

(20 citation statements)

References 93 publications

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“…While the simplest scenario is the screening of the spin 1/2 by a single screening channel, in the last years the research on Kondo systems has been extended to systems in which in addition to the spin degeneracy, there is also degeneracy in other orbital degree of freedom, leading usually to a higher symmetry of the model, such as the SU(4) one [17,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50]. The presence of both orbital and spin degrees of freedom can trigger exotic environments for developing the Kondo physics.…”

Section: Introductionmentioning

confidence: 99%

Two-stage three-channel Kondo physics for an FePc molecule on the Au(1 1 1) surface

Fernández¹,

Roura‐Bas²,

Camjayi³

et al. 2018

J. Phys.: Condens. Matter

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We study an impurity Anderson model to describe an iron phthalocyanine (FePc) molecule on Au(1 1 1), motivated by previous results of scanning tunneling spectroscopy (STS) and theoretical studies. The model hybridizes a spin doublet consisting in one hole at the [Formula: see text] orbital of iron and two degenerate doublets corresponding to one hole either in the 3d or in the 3d orbital (called π orbitals) with two degenerate Hund-rule triplets with one hole in the 3d orbital and another one in a π orbital. We solve the model using a slave-boson mean-field approximation (SBMFA). For reasonable parameters we can describe very well the observed STS spectrum between sample bias -60 mV to 20 mV. For these parameters the Kondo effect takes place in two stages, with different energy scales [Formula: see text] corresponding to the Kondo temperatures related with the hopping of the z and π orbitals respectively. There is a strong interference between the different channels and the Kondo temperatures, particularly the lowest one is strongly reduced compared with the value in the absence of the competing channel.

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Section: Introductionmentioning

confidence: 99%

Two-stage three-channel Kondo physics for an FePc molecule on the Au(1 1 1) surface

Fernández¹,

Roura‐Bas²,

Camjayi³

et al. 2018

J. Phys.: Condens. Matter

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“…The region shaded by dashed lines in Fig. 6 represents the domain in which the approximation scheme adopted in our previous works [65,66] is applicable. The region shaded by solid lines in Fig.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

“…Since the growth factor of the density contrast in the homogeneous and isotropic universe model is a function of only t, the dependence of the growth factor on µ and r ′ o in the huge void universe model can be a strong discriminator for these two models. In our previous works [65,66], we studied the linear perturbations in the huge void universe model without any distinctions between relativistic and non-relativistic perturbations, by treating the background huge void as an isotropic perturbation in the background model of the homogeneous and isotropic universe filled with dust. By contrast, the method of analysis based on the tidal approximation is applicable, even if the background void structure is highly nonlinear.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

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Newtonian self-gravitating system in a relativistic huge void universe model

Nishikawa

Nakao

Yoo

2016

J. Cosmol. Astropart. Phys.

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We consider a test of the Copernican Principle through observations of the large-scale structures, and for this purpose we study the self-gravitating system in a relativistic huge void universe model which does not invoke the Copernican Principle. If we focus on the the weakly self-gravitating and slowly evolving system whose spatial extent is much smaller than the scale of the cosmological horizon in the homogeneous and isotropic background universe model, the cosmological Newtonian approximation is available. Also in the huge void universe model, the same kind of approximation as the cosmological Newtonian approximation is available for the analysis of the perturbations contained in a region whose spatial size is much smaller than the scale of the huge void: the effects of the huge void are taken into account in a perturbative manner by using the Fermi-normal coordinates. By using this approximation, we derive the equations of motion for the weakly selfgravitating perturbations whose elements have relative velocities much smaller than the speed of light, and show the derived equations can be significantly different from those in the homogeneous and isotropic universe model, due to the anisotropic volume expansion in the huge void. We linearize the derived equations of motion and solve them. The solutions show that the behaviors of linear density perturbations are very different from those in the homogeneous and isotropic universe model. *

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“…These occupations, the tunneling matrix elements (coupling to the leads) and the voltages at the four leads can be controlled independently. The system was proposed by Büsser et al [27] to control spinpolarized currents and is being subject of intense theoretical research [28,29,31,32,34,35]. Comparing experiment with numerical-renormalization-group (NRG) calculation, Keller et al found evidence of SU(4) Kondo behavior.…”

Section: Introductionmentioning

confidence: 99%

Restoring the SU(4) Kondo regime in a double quantum dot system

Tosi

Roura‐Bas

Aligia

2015

J. Phys.: Condens. Matter

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We calculate the spectral density and occupations of a system of two capacitively coupled quantum dots, each one connected to its own pair of conducting leads, in a regime of parameters in which the total couplings to the leads for each dot Γ(i) are different. The system has been used recently to perform pseudospin spectroscopy by controlling independently the voltages of the four leads. For an odd number of electrons in the system, equal coupling to the leads Γ1 = Γ2, equal dot levels E1 = E2 and sufficiently large interdot repulsion U12 the system lies in the SU(4) symmetric point of spin and pseudospin degeneracy in the Kondo regime. In the more realistic case Γ1 ≠ Γ2, pseudospin degeneracy is broken and the symmetry is reduced to SU(2). Nevertheless, we find that the essential features of the SU(4) symmetric case are recovered by appropriately tuning the level difference δ = E2 - E1. After this tuning, the system behaves as an SU(4) Kondo one at low energies. Our results are relevant for experiments which look for signatures of SU(4) symmetry in the Kondo regime of similar systems.

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Two-point correlation function of density perturbations in a large void universe

Cited by 7 publications

References 93 publications

Two-stage three-channel Kondo physics for an FePc molecule on the Au(1 1 1) surface

Two-stage three-channel Kondo physics for an FePc molecule on the Au(1 1 1) surface

Newtonian self-gravitating system in a relativistic huge void universe model

Restoring the SU(4) Kondo regime in a double quantum dot system

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