Vacuum fluctuations of a massless spin- field around multiple cosmic strings

Aliev, Alikram N.; Hortaçsu, M.; Ozdemir, Nese

doi:10.1088/0264-9381/14/12/008

Cited by 45 publications

(21 citation statements)

References 22 publications

(32 reference statements)

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“…Here one would expect a force acting between them due to the vacuum fluctuations in analogy with the force between conducting planes whereby there should be no distance dependent singularities. This was done in [188,189] for a scalar field, in [190] for a spinor and in [191] for the electromagnetic field. Let us note that the same holds for magnetic strings, [192], and can easily be generalized to cosmic strings carrying magnetic flux.…”

Section: Vacuum Interaction Between Cosmic Stringsmentioning

confidence: 99%

“…(4.192) follow for dimensional reasons and the number σ has to be calculated. In [189] this had been done for the massless scalar field with the result σ = 4/(15π), in [190] for the massless spinor field with the same result and in [191] for the electromagnetic field with the result of σ being twice the value of the scalar field. The force acting between the strings is attractive.…”

Section: Vacuum Interaction Between Cosmic Stringsmentioning

confidence: 99%

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New developments in the Casimir effect

2001

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We provide a review of both new experimental and theoretical developments in the Casimir effect. The Casimir effect results from the alteration by the boundaries of the zero-point electromagnetic energy. Unique to the Casimir force is its strong dependence on shape, switching from attractive to repulsive as function of the size, geometry and topology of the boundary. Thus the Casimir force is a direct manifestation of the boundary dependence of quantum vacuum. We discuss in depth the general structure of the infinities in the field theory which are removed by a combination of zeta-functional regularization and heat kernel expansion. Different representations for the regularized vacuum energy are given. The Casimir energies and forces in a number of configurations of interest to applications are calculated. We stress the development of the Casimir force for real media including effects of nonzero temperature, finite conductivity of the boundary metal and surface roughness. Also the combined effect of these important factors is investigated in detail on the basis of condensed matter physics and quantum field theory at nonzero temperature. The experiments on measuring the Casimir force are also reviewed, starting first with the older measurements and finishing with a detailed presentation of modern precision experiments. The latter are accurately compared with the theoretical results for real media. At the end of the review we provide the most recent constraints on the corrections to Newtonian gravitational law and other hypothetical long-range interactions at submillimeter range obtained from the Casimir force measurements.

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Section: Vacuum Interaction Between Cosmic Stringsmentioning

confidence: 99%

Section: Vacuum Interaction Between Cosmic Stringsmentioning

confidence: 99%

New developments in the Casimir effect

2001

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“…A. C. thanks N. Ozdemir for kindly providing details of the calculations in ref. [24]. Funding from MCyT (Spain) through grant MAT2002-0495-C02-01 and from the European Union Contract No.…”

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confidence: 99%

Electronic properties of curved graphene sheets

2007

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A model is proposed to study the electronic structure of slightly curved graphene sheets with an arbitrary number of pentagon-heptagon pairs and Stone-Wales defects based on a cosmological analogy. The disorder induced by curvature produces characteristic patterns in the local density of states that can be observed in scanning tunnel and transmission electron microscopy.PACS numbers: 75.10. Jm, 75.10.Lp, 75.30.Ds The recent synthesis of single or few layers of graphite [1,2] allows to test the singular transport properties predicted in early theoretical studies [3,4,5,6] and experiments [7]. The discovery of a substantial field effect [8] and of ferromagnetic behavior [9] allows to envisage graphene as a reasonable replacement of nanotubes in electronic applications. Disorder plays a very important role in the electronic properties of low dimensional materials.Substitution of an hexagon by an n-sided ring in the hexagonal lattice without affecting the threefold coordination of the carbon atoms leads to the warping of the graphene sheet. Rings with n > 6 (n < 6), induce locally positive (negative) curvature. Inclusion of an equal number of pentagons and heptagonal rings would keep the flatness of the sheet at large scales and produce a flat structure with curved portions that would be structurally stable and have distinct electronic properties. This defects give rise to long range modifications in the electronic wave function that affect the electronics in a way different from that produced by vacancies or other impurities modelled by local potentials. Pentagon-heptagon pairs and Stone-Wales defects made of two adjacent heptagons and two pentagons form naturally in experiments of ion bombarded nanotubes as a mechanism to reduce the dangling bonds in large vacancies [10] and have been observed to form in situ in single graphene layers by highresolution transmission electron microscopy (TEM) [11].We propose a method, based on a cosmological analogy, to compute the electronic structure and transport properties of curved graphene sheets consisting of an arbitrary number of topological defects located at fixed positions of the lattice. We see that, unlike vacancies and voids, the combination of positive and negative curvature gives rise to characteristic inhomogeneous patterns in the density of states that affect the transport properties of the layers and can be observed in scanning tunnel (STM) and electron transmission spectroscopy (ETS). The present analysis can help in the experimental characterization of graphene samples and in the correct analysis of STM images. The results obtained can be related to recent Electrostatic Force Microscopy (EFM) measurements that indicate large potential differences between micrometer large regions on the surface of highly oriented graphite [12] and to the suppression of magnetorresistance in single layered graphene reported in [13]. We apply the formalism to present the corrections to the local density of states induced by pentagon-heptagon pairs and Stone-Wales defects in the...

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“…(3.28), which seems too small. However, the possible force [13] of attraction between parallel strings (or the process of string accumulation [14]) could make a bundle of multi-strings from the cosmic strings, and the constant value of rotation velocities around the bundle become much larger [27] and could be comparable to the measured one [2]. The flatness of spiral galaxy rotation curves might be their remaining property, which has been preserved from the era when the pregalaxies were made of the cosmic strings.…”

Section: Summary and Discussionmentioning

confidence: 99%

“…However, the value of rotation velocities around a bundle of a few hundred cosmic strings might be comparable to the measured value. [2] Even though such multi-string structure surrounded by the outer void region could be constructed by the possible force [13] of attraction between parallel strings or by the process of string accumulation, [14] we present a more concrete field-theoretical two-dilaton model, in illustration of the domain-wall structure [15] of strings. The flatness of spiral galaxy rotation curves might be due to the constant value of rotation velocities around the remnants of the multi-string, which has been possibly preserved because of the scaling property of the cosmic string network.…”

Section: Introductionmentioning

confidence: 99%