Cosmic acceleration and crossing of in non-minimal modified Gauss–Bonnet gravity

Modified Gauss–Bonnet, i.e., f(G) gravity is a possible explanation of dark energy. Late time cosmology for the f(G) gravity non-minimally coupled with a free massless scalar field have been investigated in Ref. [S. Nojiri, S.D. Odintsov, P.V. Tretyakov, Phys. Lett. B 651 (2007) 224, arXiv:0704.2520 [hep-th]; S. Nojiri, S.D. Odintsov, P.V. Tretyakov, Progr. Theor. Phys. Suppl. 172 (2008) 81, arXiv:0710.5232]. In this Letter we generalize the work of Ref. [S. Nojiri, S.D. Odintsov, P.V. Tretyakov, Phys. Lett. B 651 (2007) 224, arXiv:0704.2520 [hep-th]; S. Nojiri, S.D. Odintsov, P.V. Tretyakov, Progr. Theor. Phys. Suppl. 172 (2008) 81, arXiv:0710.5232] by including scalar potential in the matter Lagrangian which is non-minimally coupled with modified Gauss–Bonnet gravity. Also we obtain the conditions for having a much more amazing problem than the acceleration of the universe, i.e. crossing of ω=−1, in f(G) non-minimally coupled with tachyonic Lagrangian.     

The effects of the N atom collective Lamb shift on single photon superradiance

The problem of single photon collective spontaneous emission, a.k.a. superradiance, from N atoms prepared by a single photon pulse of wave vector k₀ has been the subject of recent interest. It has been shown that a single photon absorbed uniformly by the N atoms will be followed by spontaneous emission in the same direction [M. Scully, E. Fry, C.H.R. Ooi, K. Wodkiewicz, Phys. Rev. Lett. 96 (2006) 010501; M. Scully, Laser Phys. 17 (2007) 635]; and in extensions of this work we have found a new kind of cavity QED in which the atomic cloud acts as a cavity containing the photon [A.A. Svidzinsky, J.T. Chang, M.O. Scully, Phys. Rev. Lett. 100 (2008) 160504]. In most of our studies, we have neglected virtual photon (“Lamb shift”) contributions. However, in a recent interesting paper, Friedberg and Mannassah [R. Friedberg, J.T. Manassah, Phys. Lett. A 372 (2008) 2514] study the effect of virtual photons investigating ways in which such effects can modify the time dependence and angular distributions of collective single photon emission. In the present Letter, we show that such virtual transitions play no essential role in our problem. The conclusions of [M. Scully, E. Fry, C.H.R. Ooi, K. Wodkiewicz, Phys. Rev. Lett. 96 (2006) 010501; M. Scully, Laser Phys. 17 (2007) 635; A.A. Svidzinsky, J.T. Chang, M.O. Scully, Phys. Rev. Lett. 100 (2008) 160504] stand as published. However, the N atom Lamb shift is an interesting problem in its own right and we here extend previous work both analytically and numerically.     

Canonical connections of Finsler metrics and Finslerian connections on Riemannian metrics

A concept of canonical connection of a Finsler metric is developed. Connections that are compatible with Finsler metrics are compared with the canonical connection itself. They are also compared with the corresponding Cartan connection. A necessary and sufficient condition on metric Finsler connections is given for the metric to be Riemannian. This study unearths different ways in which Finsler geometry could be used to generalize the theory of general relativity.     

Bi-metric pseudo-Finslerian spacetimes

Finsler spacetimes have become increasingly popular within the theoretical physics community over the last two decades. However, because physicists need to use pseudo-Finsler structures to describe propagation of signals, there will be nonzero null vectors in both the tangent and cotangent spaces — this causes significant problems in that many of the mathematical results normally obtained for “usual” (Euclidean signature) Finsler structures either do not apply, or require significant modifications to their formulation and/or proof. We shall first provide a few basic definitions, explicitly demonstrating the interpretation of bi-metric theories in terms of pseudo-Finsler norms. We shall then discuss the tricky issues that arise when trying to construct an appropriate pseudo-Finsler metric appropriate to bi-metric spacetimes. Whereas in Euclidian signature the construction of the Finsler metric typically fails only at the zero vector, in Lorentzian signature the Finsler metric is typically ill-defined on the entire null cone. Consequently it is not a good idea to try to encode bi-metricity into pseudo-Finsler geometry. One has to be very careful when applying the concept of pseudo-Finsler geometry in physics.     

Piezonuclear reactions - do they really exist?

In a number of recent articles in this journal F. Cardone and collaborators have claimed the observation of several striking nuclear phenomena which they attribute to “piezonuclear reactions”. One such claim [F. Cardone, R. Mignani, A. Petrucci, Phys. Lett. A 373 (2009) 1956] is that subjecting a solution of ²²⁸Th to cavitation leads to a “transformation” of thorium nuclei that is 10⁴ times faster than the normal nuclear decay for this isotope. In a “Comment” [G. Ericsson, S. Pomp, H. Sjöstrand, E. Traneus, Phys. Lett. A 373 (2009) 3795] to the thorium work, we have criticized the evidence provided for this claim. In a “Reply” [F. Cardone, R. Mignani, A. Petrucci, Phys. Lett. A 373 (2009) 3797] Cardone et al. answer only some minor points but avoid addressing the real issue. The information provided in their Reply displays a worrying lack of control of their experimental situation and the data they put forward as evidence for their claims. We point out several shortcomings and errors in the described experimental preparations, set-up and reporting, as well as in the data analysis. We conclude that the evidence presented by Cardone et al. is insufficient to justify their claims of accelerated thorium decay (by “piezonuclear reactions” or otherwise).     

Comment on “Correlation between future and past photon events” by A. Widom et al.

Widom, Srivastava, and Sassaroli [Phys. Lett. A 203 (1995) 255] have published a calculation which purports to show that “future events can effect present events”. In this note an error in their calculation is identified.     

Missing ordinal patterns in correlated noises

Recent research aiming at the distinction between deterministic or stochastic behavior in observational time series has looked into the properties of the “ordinal patterns” [C. Bandt, B. Pompe, Phys. Rev. Lett. 88 (2002) 174102]. In particular, new insight has been obtained considering the emergence of the so-called “forbidden ordinal patterns” [J.M. Amigó, S. Zambrano, M.A. F Sanjuán, Europhys. Lett. 79 (2007) 50001]. It was shown that deterministic one-dimensional maps always have forbidden ordinal patterns, in contrast with time series generated by an unconstrained stochastic process in which all the patterns appear with probability one. Techniques based on the comparison of this property in an observational time series and in white Gaussian noise were implemented. However, the comparison with correlated stochastic processes was not considered. In this paper we used the concept of “missing ordinal patterns” to study their decay rate as a function of the time series length in three stochastic processes with different degrees of correlation: fractional Brownian motion, fractional Gaussian noise and, noises with f^−k power spectrum. We show that the decay rate of “missing ordinal patterns” in these processes depend on their correlation structures. We finally discuss the implications of the present results for the use of these properties as a tool for distinguishing deterministic from stochastic processes.     

Pt-induced structures on Si(1 1 0) studied by STM

The structures induced by platinum (Pt) adsorption on Si(1 1 0) surface have been studied by scanning tunneling microscopy (STM) for coverage up to 2 monolayers (ML). Three surface phases have been found to form: “5×4”, “13×2” and “6×5” for Pt coverages 0.3, 0.5 and 1 ML respectively. All structures are formed by one-dimensional rows aligned along the direction. At the coverage >1 ML islands of, probably, Pt silicide start to form in form of 1D nanowires.     

Overwriting information: Correlations,physical costs,and environment models

In this sequel to our previous study of the entropic and energetic costs of information erasure [N.G. Anderson, Phys. Lett. A 372 (2008) 5552], we consider direct overwriting of classical information encoded in a quantum-mechanical memory system interacting with a heat bath. Lower bounds on physical costs of overwriting – in both “single-shot” and “sequential” overwriting scenarios – are obtained from globally unitary quantum dynamics and entropic inequalities alone, all within a referential approach that grounds information content in correlations between physical system states. A heterogeneous environment model, required for consistent treatment of sequential overwriting, is introduced and used to establish and relate bounds for various cases.     

Reply to the Comment by F. Kožíšek et al. on “Evidence for the existence of stable-water-clusters at room temperature and normal pressure” [Phys. Lett. A 373 (2009) 3872]

After discussing various points raised in a recent comment by F. Ko?íšek et al., who claim that our Letter “Evidence for the existence of stable-water-clusters at room temperature and normal pressure” (Phys. Lett. A 373 (2009) 3872) is unclear and the evidence is scant, we conclude that their arguments are wrong.     

Explicit Formula for the Natural and Projectively Equivariant Quantization

In [Prog Theor Phys Suppl 49(3):173–196, 1999], Lecome conjectured the existence of a natural and projectively equivariant quantization. In [math.DG/0208171, Submitted], Bordemann proved this existence using the framework of Thomas–Whitehead connections. In [Lett Math Phys 72(3):183–196, 2005], we gave a new proof of the same theorem thanks to the Cartan connections. After these works, there was no explicit formula for the quantization. In this paper, we give this formula using the formula in terms of Cartan connections given in [Lett Math Phys 72(3):183–196, 2005]. This explicit formula constitutes the generalization to any order of the formulae at second and third orders soon published by Bouarroudj in [Lett Math Phys 51(4):265–274, 2000] and [C R Acad Sci Paris Sér I Math 333(4):343–346, 2001].     

The Transition Metal Complex (η-C5H5)Fe(CO)2Cl in Its Neutral, Anionic, and Cationic States—Density Functional Theory Calculations and Mass Spectroscopical Investigations

In this contribution, we report density functional theory calculations on the transition metal complex (η⁵-C₅H₅)Fe(CO)₂Cl and its fragments in differently charged states (anionic, neutral, cationic). The results are compared to literature data. The work is motivated by the long-term objective of a charge reversal or “NeNePo” (negative-neutral-positive) experiment (Wolf, Sommerer, Rutz, Schreiber, Leisner, Wöste, and Berry, Phys. Rev. Lett.74, 4177-4180 (1995)). The calculated data explain results from preliminary mass spectroscopical experiments on anions. The calculations show that the complex could be well suited for a successful “NeNePo” experiment.     

Study of Strange Quark Mass in CFL Phase

[1]M.Alford,K.Rajagopal,and F.Wilczek,Phys.Lett.B 422 (1998) 247; Nucl.Phys.B 537 (1999) 443. [2]M.Gyulassy and L.McLerran,arXiv:nucl-th/0405013;E.V.Shuryak,arXiv:hep-ph/0405066. [3]K.Rajagopal and F.Wilczek,hep-ph/0011333. [4]M.Alford,Chris Kouvaris,and K.Rajagopal,hepph/0406137. [5]Y.Nambu and G.Jona-Lasinio,Phys.Rev.122 (1961)345. [6]R.T.Cahill and C.D.Roberts,Phys.Rev.D 32 (1985)2419. [7]R.T.Cahill and Susan M.Ganner,hep-ph/9812491. [8]A.W.Steiner,S.Reddy,and M.Prakash,Phys.Rev.D 66 (2002) 094007. [9]P.Amore,M.C.Birse,J.A.McGovern,and N.R.Walet,Phys.Rev.D 65 (2002) 074005. [10]M.Alford and K.Rajagopal,JHEP 0206 (2002) 031. [11]Xiao-Fu Li,Yu-Xin Liu,Hong-Shi Zong,and En-GuangZhao,Phys.Rev.C 58 (1998) 1195. [12]H.Reinhardt,Phys.Lett.B 244 (1990) 2. [13]Steven Weinberg,The Quantum Theory of Fields,Vol.2,Cambridge University Press,Cambridge (1996) p.348.     

Probing compositeness with Higgs Boson decays at the LHC

We study how massive ghost-free gravity \(f(R)\) -modified theories, MGFTs, can be encoded into generic off-diagonal Einstein spaces. Using “auxiliary” connections completely defined by the metric fields and adapted to nonholonomic frames with associated nonlinear connection structure, we decouple and integrate in certain general forms the field equations in MGFT. Imposing additional nonholonomic constraints, we can generate Levi-Civita, LC, configurations and mimic MGFT effects via off-diagonal interactions of effective Einstein and/or Einstein–Cartan gravity with nonholonomically induced torsion. We show that imposing nonholonomic constraints it is possible reproduce very specific models of massive \(f(R)\) gravity studied in Cai et al. (arXiv:1307.7150, 2013), Klusoňet al. (Phys Lett B 726:918, 2013), Nojiri and Odintov (Phys Lett B 716:377, 2012) and Nojiri et al. (JCAP 1305:020, 2013). The cosmological evolution of ghost-free off-diagonal Einstein spaces is investigated. Certain compatibility of MGFT cosmology to small off-diagonal deformations of \(\Lambda \) CDM models is established.     

Comment on “Towards a large deviation theory for strongly correlated systems”

I comment on a recent paper by Ruiz and Tsallis [Phys. Lett. A 376 (2012) 2451] claiming to have found a “q-exponential” generalization of the large deviation principle for strongly correlated random variables. I show that the basic scaling results that they find numerically can be reproduced with a simple example involving independent random variables, and are not specifically related to the q-exponential function. In fact, identical scaling results can be obtained with any other power-law deformations of the exponential. Thus their results do not conclusively support their claim of a q-exponential generalization of the large deviation principle.     

Simulation of turbulence in mode-locked lasers

We establish the connection between a paper by Kartner et al. [F.X. Kartner, D.M. Zumbuhl, N. Matuschek, Phys. Rev. Lett. 82 (1999) 4428] entitled “Turbulence in mode-locked lasers”, and earlier work on the role of noise in mode-locked laser systems. We present numerical results that broadly support the analytical results of Kartner et al.     

Global Monopole in Kalb–Ramond Background

In recent, S. SenGupta and S. Sur [Phys. Lett. B 502 (2001) 350] have obtained static vacuum solutions of the gravitational field equations in back ground space time with torsion. The torsion is identified with the field strength of a second-rank anti-symmetric tensor field, namely Kalb-Ramond field. In this work, we present the solutions for the metric outside a monopole resulting from the breaking of a global 0(3) symmetry in Kalb-Ramond background. A comparison is made with the corresponding results predicted by general relativity.     

Rebuttal on “anti-gravitation” by S. Hossenfelder

Hossenfelder proposes in [S. Hossenfelder, Phys. Lett. B 636 (2006) 119] and [S. Hossenfelder, gr-qc/0605083] a symmetry between gravitating and anti-gravitating particles by superposing a negative charge to classical relativity. This Letter explicitly shows that the latter proposal does not address any of the difficulties that arise in such context. On the contrary, the “world-lines” of the anti-gravitating particles are defined as observer-dependent entities and no attempt whatsoever to dynamically restore local boost invariance is made. Both papers simply focus on the erroneous construction of a new bundle attached to a preferred timelike vector field, although the author gives the impression that no such preference is needed.