Authors Of Ref Research Articles

Free energy and specific heat near a quantum critical point of a metal

We analyze free energy and specific heat for fermions interacting with gapless bosons at a quantum-critical point (QCP) in a metal. We use the Luttinger-Ward-Eliashberg formula for the free energy in the normal state, which includes contributions from bosons, fermions, and their interaction, all expressed via fully dressed fermionic and bosonic propagators. The sum of the last two contributions is the free energy $F_\gamma$ of an effective low-energy model of fermions with boson-mediated dynamical 4-fermion interaction $V (\Omega_m) \propto 1/|\Omega_m|^\gamma$ (the $\gamma-$model). This purely electronic model has been used to analyze the interplay between non-Fermi liquid (non-FL) behavior and pairing near a QCP, which are both independent of the upper energy cutoff $\Lambda$. However, the specific heat $C_\gamma (T)$, obtained from $F_\gamma$, does depend on $\Lambda$. We argue that this dependence is spurious and cancels out, once we include the contribution from bosons. We compare our $C(T)$ with the one obtained within the $\gamma-$model using recently proposed regularization of $F_\gamma$. We argue that for $\gamma <1$, the full $C(T)$ and the regularized $C_\gamma (T)$ differ by a $\gamma-$dependent prefactor, while for $\gamma >1$, the full $C(T)$ is the sum of $ C_\gamma (T)$ and the specific heat of free bosons with fully dressed mass. For these $\gamma$, $C_\gamma (T)$ is negative. The authors of Ref. [1] argued that a negative $ C_\gamma (T)$ implies that the normal state becomes unstable at some distance to a QCP. In our calculation, both terms in $C(T)$ come from the same source, and $ C_\gamma (T)$ is smaller as long as vertex corrections can be safely neglected. We then argue that the normal state remains stable even at a QCP.

On The Calculation Of The Average Value Of The Strong Coupling Constant α_s, Using The Best Linear Unbiased Estimator (Blue) Method

Experiments to measure a single physical quantity often produce several estimates based on the same data, and which are hence correlated. We describe how to combine these correlated estimates in order to provide the best single answer, and also how to check whether the correlated estimates are mutually consistent.&#x0D; We discuss the properties of our technique, and illustrate its application by using it for a specific experiment which measured the strong coupling constant .In this work, we computed the mean value of the strong coupling constant by relying on the three measurement values of ATLAS.&#x0D; We present a method to calculate the mean value of the strong coupling constant and the uncertainty about this value at a centre of-mass energy 7Tev, 8Tev and 13Tev based on the results obtained in ref[1].&#x0D; We get the result , we will compare it with the result obtained by the authors of ref[1], which is .

Two-loop five-parton leading-colour finite remainders in the spinor-helicity formalism

We present all two-loop five-parton leading-colour finite remainders in the spinor-helicity formalism by analysing numerical evaluations of their known expressions in terms of Mandelstam invariants. Recasting them in terms of spinor-helicity variables allows us to obtain expressions which are more compact, faster to evaluate, numerically more stable and manifestly free from poles of higher order than necessary. At the same time, due to the better scaling of our reconstruction strategy with the complexity of the input, we required one order of magnitude fewer numerical samples to complete the analytical reconstruction than were needed by the authors of ref. [1], albeit using higher numerical working precision. This places our reconstruction technique as an alternative to the finite-field single-numerator reconstruction for future applications.

QCD axion on hilltop by a phase shift of \u03c0.

We show that the initial misalignment angle of the QCD axion (or axion-like particles) can be set very close to π, if the QCD axion has a mixing with another heavy axion which induces the phase shift ≈ π after inflation. In the simplest case, the heavy axion plays the role of the inflaton, and we call such inflation as “πnflation”. The basic idea was first proposed by Daido and the present authors in ref. [1] in 2017 and more recently discussed in ref. [2]. We show that the QCD axion with a decay constant fa ≳ 3 × 109 GeV can explain dark matter by the πnflation mechanism. A large fraction of the parameter region has an overlap with the projected sensitivity of ORGAN, MADMAX, TOORAD and IAXO. We also study implications for the effective neutrino species and isocurvature perturbations. The πnflation can provide an initial condition for the hilltop inflation in the axion landscape, and in a certain set-up, a chain of the hilltop inflation may take place.

Scalar quasinormal modes of Kerr−AdS5

An analytic expression for the scalar quasinormal modes of the generic, spinning Kerr-$\mathrm{AdS_5}$ black holes was previously proposed by the authors in ref. 1, in terms of transcendental equations involving the Painlev\'e VI (PVI) $\tau$ function. In this work, we carry out a numerical investigation of the modes for generic rotation parameters, comparing implementations of expansions for the PVI $\tau$ function both in terms of conformal blocks (Nekrasov functions) and Fredholm determinants. We compare the results with standard numerical methods for the subcase of Schwarzschild black holes. We then derive asymptotic formulas for the angular eigenvalues and the quasinormal modes in the small black hole limit for generic scalar mass and discuss, both numerically and analytically, the appearance of superradiant modes.

Comment on “Cosmic evolution in Brans-Dicke chameleon cosmology” by Mubasher Jamil et al.

The authors of Ref. \cite{1-2}, investigated cosmic evolution in an external interacting model of scalar tensor gravity namely Brans Dicke chameleon scenario. The procedure of this work contains novelties but, it shall be observed from this comment, their report faces three fundamental drawbacks. One of them concerns the energy conservation equation, and the other two flaws are about mathematical mistakes. In the scalar tensor gravity models, a well-known method, in order to obtain conservation equation one must combine Friedmann equations with modified Klein-Gordon equation. But in Ref. \cite{1-2}, by virtue of the mentioned approach one would not be able to achieve a correct result for conservation equation. In addition, one can readily realize that their mathematical mistakes lead to different results compared to the present report.

4D N = 1 SYM supercurrent on the lattice in terms of the gradient flow

The gradient flow [1–5] gives rise to a versatile method to construct renor-malized composite operators in a regularization-independent manner. By adopting this method, the authors of Refs. [6–9] obtained the expression of Noether currents on the lattice in the cases where the associated symmetries are broken by lattice regularization. We apply the same method to the Noether current associated with supersymmetry, i.e., the supercurrent. We consider the 4D N = 1 super Yang–Mills theory and calculate the renormalized supercurrent in the one-loop level in the Wess–Zumino gauge. We then re-express this supercurrent in terms of the flowed gauge and flowed gaugino fields [10].

Comment on “Lattice gluon and ghost propagators and the strong coupling in pure SU(3) Yang-Mills theory: Finite lattice spacing and volume effects”

The authors of ref. Phys.Rev. D94 (2016) no.1, 014502 reported about a careful analysis of the impact of lattice artifacts on the $SU(3)$ gauge-field propagators. In particular, they found that the low-momentum behavior of the renormalized propagators depends on the lattice bare coupling and interpreted this fact as the result of it being affected by finite lattice spacing artifacts. We do not share this interpretation and present here a different and more suitable explanation for these results.

Two-atom interaction energies with one atom in an excited state: van der Waals potentials versus level shifts

I revisit the problem of the interaction between two dissimilar atoms with one atom in an excited state, recently addressed by the authors of Refs.[1-3], and for which precedent approaches have given conflicting results. In the first place, I discuss to what extent Refs.[1], [2] and [3] provide equivalent results. I show that the phase-shift rate of the two-atom wave function computed in Ref.[1], the van der Waals potential of the excited atom in Ref.[2] and the level shift of the excited atom in Ref.[3] possess equivalent expressions in the quasistationary approximation. In addition, I show that the level shift of the ground state atom computed in Ref.[3] is equivalent to its van der Waals potential. A diagrammatic representation of all those quantities is provided. The equivalences among them are however not generic. In particular, it is found that for the case of the interaction between two identical atoms excited, the phase-shift rate and the van der Waals potentials differ. Concerning the conflicting results of previous approaches in regards to the spatial oscillation of the interactions, I conclude in agreement with Refs.[1,3] that they refer to different physical quantities. The impacts of free-space dissipation and finite excitation rates on the dynamics of the potentials are analyzed. In contrast to Ref.[3], the oscillatory versus monotonic spatial forms of the potentials of each atom are found not to be related to the reversible versus irreversible nature of the excitation transfer involved.

Comment on “High-temperature soft magnetic properties of antiperovskite nitrides ZnNFe3 and AlNFe3” by Yankun Fu, Shuai Lin, and Bosen Wang, J. Magn. Magn. Mater. 378 (2015) 54–58

The authors of the aforementioned manuscript have recently claimed the synthesis of the ternary nitrides ZnNFe3 (=ZnFe3N) and AlNFe3 (=AlFe3N), ordered substituted variants of the binary phase γ‘-Fe4N [1]. While soft ferromagnets of such kind are presently attracting lots of attention, their history dates back for more than half a century. In particular, Al-substituted γ‘-Fe4N has already been mentioned in 1961 [2], and the existence of AlFe3N has also been claimed in 2009 [3] from a two-step ammonolysis reaction combining a high-temperature sintering step and a low-temperature nitriding reaction [4]. Nonetheless, one of us had to withdraw the latter claim after finding out, by means of scanning-electron microscopy and elemental mapping, that all samples of “AlFe3N” consisted of an intimate solid mixture of γ‘-Fe4N and amorphous Al2O3[5]. From what follows, we have strong reasons to believe that the authors of Ref. [1] overlooked our findings [5] and also did not synthesize ZnFe3N and AlFe3N.

Erratum: Next-gen immunohistochemistry

Nat. Methods 11, 381–383 (2014); published online 28 March 2014; corrected after print 23 May 2014 In the version of this article initially published, the surname of the first author of ref. 1 was misspelled as “Geisen”; the correct spelling is “Giesen.” The error has been corrected in the HTML and PDF versions of the article.

Anomalous vibrational properties of cubic boron arsenide

BoronbasedIII-Vcompounds withzincblendelatticehavebeen best known for the excellent mechanical and thermalproperties of cubic boron nitride (c-BN). Cubic BN has thehighestsecondtodiamondhardnessandthermalconductivity,highbulkmodulus,alowfrictioncoefficient,andhighmeltingpoint [1]. Recently, BAs, another member of this family,is predicted to have thermal conductivity on par with thatof diamond [2]. This result is somewhat surprising for theseries c-BN, BP, BAs, and BSb, where the most importantproperties needed for an outstanding thermal conductivityvary in a way that BAs is not particularly distinguishable.The authors of Ref. [2] ascribe the diamondlike value ofthermalconductivitytoanadvantageouscombinationoflatticevibrationalpropertiesofBAsasalargefrequencygapbetweenoptical and acoustic modes, close packing (bunching) ofacoustic branches, and weak influence of isotopes on phononscattering. Cubic BAs, however, has been studied very little,andmanyofthecomputationallypredictedpropertiesstillneedto be tested experimentally.In this paper, we present a Raman study of the vibrationalproperties of BAs complemented with density-functionalperturbation theory (DFPT) lattice dynamics simulations. TheRamanspectraofBAspreparedwithnaturalisotopicabundantboron

Charge Density Wave Transition in EuAl4

Charge Density Wave Transition in EuAl₄

Reply to Comment on “Experimental Test of an Event-Based Corpuscular Model Modification as an Alternative to Quantum Mechanics”

We have presented an experimental result, where we show that the predictions of an Event-Based Corpuscular Model (EBCM) from Ref. 2, a model that belongs to a class of non-ergodic models first described by Buonomano, are inconsistent with our measurements. We concluded that traditional quantum mechanics adequately describes our experiment, where pure single photons were used, and that our findings agree with earlier verification experiments by Summhammer, where a poissonian source of heavy particles was used. In their comment, Michielsen et al. disagree with the above conclusions. The central point of their argument is that EBCM predictions would be compatible with the observation, if the Mach–Zehnder interferometer (MZI) under test is modeled as a single system, and not as two independent, non-communicating beam splitters (BS). Unfortunately, the physics of interaction and a quantitative model of communication among the parts of MZI that would make it possible to reduce the model to effectively one memory register are not offered. Furthermore, no modification for a verification experiment that would guarantee the absence of an unspecified interaction is offered. An argument resorting to communication between the MZI parts is not a surprise. It is identical to invoking a locality loophole in Bell inequalities: when one considers communication among the different parts of the experimental apparatus, it is well known that hidden variable models can reproduce the results of Quantum Mechanics (QM). But by invoking an undescribed locality loophole, the EBCM and its verification experiment largely loses its appeal, because it becomes a sub-class of hidden variable theories falsifiable via a locality loophole free Bell test. In this sense, the class of local variable theories with noncommunicating memories per each optical element was by far more interesting and unique, because they provide an independent way for testing. We point out that the argument of Michielsen et al. begs the question by suggesting that more experiments are needed while providing no details on how one may avoid any and all interactions that may lead to replacing the two independent registers in the two beam splitters (as originally proposed in their model) with one collective register. Ultimately, we believe that it is not possible to suggest an experiment, even in principle, that would allow a test similar to that from Ref. 2 with the two beam splitters outside of the light cone, i.e., where one could guarantee that no sub-luminal communication occurs, because the ‘‘message carriers’’ are photons that travel with a luminal speed. Given that this loophole can never be closed, it is really hard to define what ‘‘independent’’ means. In view of this, it is unfortunate that Michielsen et al. do not offer any discussion on how to ensure that optical parts are ‘‘independent’’. Particularly, no details are offered on how to reduce independent BSs to a single system that guarantees that the functionality of the device before and after reduction is consistent with QM. How would that reduction occur in nature? Is this reduction adiabatic or discontinuous? How can one control the transition from a set of non-interacting EBCM elements to a single EBCM element? In other words, where are new registers located, and why are they to be moved from the BS as initially asserted, and how does such a device reproduce laws of QM before, during and after such a drastic transition? We believe that, by invoking a non-formalized locality loophole, Michielsen et al. commend the experimental efforts of Ref. 1, acknowledging that all other aspects of the experiment are flawless. That is, the authors of Ref. 1 conducted a fair experiment, in strict accordance with their initial theoretical proposal, and free of an unintentional bias. In conclusion, the comment does not explain how and why the EBCM model is modified to overcome the Ref. 1 test. Further, it neither clarifies the relevance of the model in its new version nor proposes new tests of it. By invoking a non-formalized locality loophole, the authors implicitly moved their model to a much larger class of local realism models.

Monitoring Anesthesiologists’ and Anesthesiology Departments’ Managerial Performance

Monitoring Anesthesiologists’ and Anesthesiology Departments’ Managerial Performance

Erratum: Experimental demonstration of optical transport, sorting and self-arrangement using a 'tractor beam'

Nature Photon. 7, 123–127 (2013); published online 20 January 2013; corrected after print 6 February 2013. In this version of this Letter originally published, the surname of the first author of ref. 26 should have been “Zhang” and the reference should have read: 26. Zhang, L. & Marston, P. L. Geometrical interpretation of negative radiation forces of acoustical Bessel beams on spheres.

Comment on “Fermi surface reconstruction in hole-dopedt−Jmodels without long-range antiferromagnetic order”

The authors of Ref.1introduced a new microscopicconstruction of a fractionalized Fermi liquid (FL∗) phase inat−Jmodel in a regime where no long-range order ispresent and no symmetry is broken. Such a FL∗-like modelof small hole pockets enclosing a volume determined by thedensity of dopant carriers alone is most suitable to describethe pseudogap phase of the cuprate superconductors. Thistheoretical framework is in good agreement with a numberof recent experimental results

Response to “Stripy Nanoparticles Revisited”

In a paper entitled "Stripy Nanoparticles Revisited", Levy and co-workers contest the interpretation of scanning tunneling microscopy images of monolayer protected gold nanoparticles that our group has presented. We show that the two arguments they use are based on flawed assumptions and contradict each other. We also show new evidence for the existence of stripe-like domains on mixed monolayer-coated gold nanoparticles. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Comment on “Finite Size Corrections to the Radiation Reaction Force in Classical Electrodynamics”

In [1, arXiv:1005.2617] effective field theory methods have been employed to compute the equations of motion of a spherically symmetric charged shell of radius R, taking into account the radiation reaction force exerted by the shell's own electromagnetic field up to O(R^2). The authors of Ref. [1] have stated that the known result for the self force of the shell as can be found from Eq. (16.28) of the textbook of Jackson [2] (see also Chap. 4 in the review of Pearle [3]) is incorrect, in that the term linear in R should be absent. We claim that this conclusion of Ref. [1] is incorrect, and that the textbook result, Eq. (1) does hold.

Erratum: Phonon-cavity electromechanics

Nature Physics http://dx.doi.org/10.1038/nphys2277 (2012); 1 April 2012; corrected after print 26 April 2012. In the version of this Letter originally published, the name of the first author of ref. 21 should have read 'De Liberato, S.'. This error has been corrected in the HTML and PDF versions of the Letter.