Increasing optical metamaterials functionality

Gold Split Ring Resonators (SRRs) were fabricated on silicon substrates by electron beam lithography and lift-off, with overall dimensions of approximately 200 nm. Reflectance spectra from the SRRs are similar to those published elsewhere. New devices are proposed based on the additional functionality afforded by the use of a silicon substrate

On the Summation of Feynman Graphs

A functional method to achieve the summation of all Feynman graphs relevant to a particular Field Theory process is suggested, and applied to QED, demonstrating manifestly gauge invariant calculations of the dressed photon propagator in approximations of increas- ing complexity. These lead in a natural way to the extraction of the leading logarithmic divergences of every perturbative order, and to a demonstration of the possible cancellation of all such divergences in the calculation of the (inverse of the) photon's wavefunction renormalization constant Z3. This analysis provides a qualitative understanding of why the measured value of the renormalized fine structure constant is, approximately, 1/137

The Influence of the Degree of Heterogeneity on the Elastic Properties of Random Sphere Packings

The macroscopic mechanical properties of colloidal particle gels strongly depend on the local arrangement of the powder particles. Experiments have shown that more heterogeneous microstructures exhibit up to one order of magnitude higher elastic properties than their more homogeneous counterparts at equal volume fraction. In this paper, packings of spherical particles are used as model structures to computationally investigate the elastic properties of coagulated particle gels as a function of their degree of heterogeneity. The discrete element model comprises a linear elastic contact law, particle bonding and damping. The simulation parameters were calibrated using a homogeneous and a heterogeneous microstructure originating from earlier Brownian dynamics simulations. A systematic study of the elastic properties as a function of the degree of heterogeneity was performed using two sets of microstructures obtained from Brownian dynamics simulation and from the void expansion method. Both sets cover a broad and to a large extent overlapping range of degrees of heterogeneity. The simulations have shown that the elastic properties as a function of the degree of heterogeneity are independent of the structure generation algorithm and that the relation between the shear modulus and the degree of heterogeneity can be well described by a power law. This suggests the presence of a critical degree of heterogeneity and, therefore, a phase transition between a phase with finite and one with zero elastic properties.Comment: 8 pages, 6 figures; Granular Matter (published online: 11. February 2012

A New Approach to Analytic, Non-Perturbative and Gauge-Invariant QCD

Following a previous calculation of quark scattering in eikonal approximation, this paper presents a new, analytic and rigorous approach to the calculation of QCD phenomena. In this formulation a basic distinction between the conventional "idealistic" description of QCD and a more "realistic" description is brought into focus by a non-perturbative, gauge-invariant evaluation of the Schwinger solution for the QCD generating functional in terms of the exact Fradkin representations of the Green's functional and the vacuum functional. Because quarks exist asymptotically only in bound states, their transverse coordinates can never be measured with arbitrary precision; the non-perturbative neglect of this statement leads to obstructions that are easily corrected by invoking in the basic Lagrangian a probability amplitude which describes such transverse imprecision. The second result of this non-perturbative analysis is the appearance of a new and simplifying output called "Effective Locality", in which the interactions between quarks by the exchange of a "gluon bundle" - which "bundle" contains an infinite number of gluons, including cubic and quartic gluon interactions - display an exact locality property that reduces the several functional integrals of the formulation down to a set of ordinary integrals. It should be emphasized that "non-perturbative" here refers to the effective summation of all gluons between a pair of quark lines, but does not (yet) include a summation over all closed-quark loops which are tied by gluon-bundle exchange to the rest of the "Bundle Diagram". As an example of the power of these methods we offer as a first analytic calculation the quark-antiquark binding potential of a pion, and the corresponding three-quark binding potential of a nucleon, obtained in a simple way from relevant eikonal scattering approximations.Comment: 38 pages, 3 figures in REVTeX. Collections of follow-on work of Eur. Phys. J. C65, pp. 395-411 (2010). arXiv admin note: text overlap with arXiv:1103.4179, arXiv:1104.4663, arXiv:1003.293

Non-perturbative QCD amplitudes in quenched and eikonal approximations

Even though approximated, strong coupling non-perturbative QCD amplitudes remain very difficult to obtain. In this article, in eikonal and quenched approximations, physical insights are presented that rely on the newly-discovered property of Effective Locality.Comment: Revised version (28 pages and 1 figure in REVTeX). Follow-up work of Eur. Phys. J. C65, pp. 395-411 (2010), (arXiv:1204.2038 [hep-ph]), and Ann. Phys. 327, pp. 2666-2690 (2012), (arXiv:1203.6137 [hep-ph]

Exact Path-Integral Representations for the TT-Matrix in Nonrelativistic Potential Scattering

Several path integral representations for the $T$-matrix in nonrelativistic potential scattering are given which produce the complete Born series when expanded to all orders and the eikonal approximation if the quantum fluctuations are suppressed. They are obtained with the help of "phantom" degrees of freedom which take away explicit phases that diverge for asymptotic times. Energy conservation is enforced by imposing a Faddeev-Popov-like constraint in the velocity path integral. An attempt is made to evaluate stochastically the real-time path integral for potential scattering and generalizations to relativistic scattering are discussed.Comment: 6 pages, 2 figures. Contribution to the workshop "Relativistic Description of Two- and Three-Body Systems in Nuclear Physics", ETC*, October 19-23, 2009. v2: typo corrected, matches published version + additional reference

Prevalensi miopia pada murid SD GMIM II Kauditan Kabupaten Minahasa Utara Propinsi Sulawesi Utara

Myopia umumnya dideraita oleh usia usia sekolah antara 7 – 17 tahun. Walaupun gangguan penglihatan ini masih bisa dikoreksi dengan pe,berian kaca mata, akan tetapi gangguan ini banyak menimbulkan masalah belajar pada anak usia sekolah. Tujuan penelitian ini adalah untuk mendapatkan gambaran kesehatan mata khususnya gambaran kemampuan visus pada murid sekolah SD GMIM II Kauditan, Kabupaten Minahasa Utara, Propinsi Sulawesi Utara. Hasil penelitian menunjukan bahwa prevalensi myopia pada SD GMIM II Kauditan, Kabupaten Minahasa Utara sebesar 25,3%, dengan sebaran merata pada murid laki-laki dan perempuan, dan terjadi pada satu mata atau kedua mata. Kesimpulan bahwa gangguan visus myopia masih kerap terjadi pada anak usia sekolah, dan perlu penelitian lanjut tentang faktor resiko terjadinya myopia ini sehingga edukasi dan tindakan khusus lainnya bisa diambil untuk penanganan masalah gangguan visus ini.  Myopia umumnya dideraita oleh usia usia sekolah antara 7 – 17 tahun. Walaupun gangguan penglihatan ini masih bisa dikoreksi dengan pe,berian kaca mata, akan tetapi gangguan ini banyak menimbulkan masalah belajar pada anak usia sekolah. Tujuan penelitian ini adalah untuk mendapatkan gambaran kesehatan mata khususnya gambaran kemampuan visus pada murid sekolah SD GMIM II Kauditan, Kabupaten Minahasa Utara, Propinsi Sulawesi Utara. Hasil penelitian menunjukan bahwa prevalensi myopia pada SD GMIM II Kauditan, Kabupaten Minahasa Utara sebesar 25,3%, dengan sebaran merata pada murid laki-laki dan perempuan, dan terjadi pada satu mata atau kedua mata. Kesimpulan bahwa gangguan visus myopia masih kerap terjadi pada anak usia sekolah, dan perlu penelitian lanjut tentang faktor resiko terjadinya myopia ini sehingga edukasi dan tindakan khusus lainnya bisa diambil untuk penanganan masalah gangguan visus ini.

Invasive Allele Spread under Preemptive Competition

We study a discrete spatial model for invasive allele spread in which two alleles compete preemptively, initially only the "residents" (weaker competitors) being present. We find that the spread of the advantageous mutation is well described by homogeneous nucleation; in particular, in large systems the time-dependent global density of the resident allele is well approximated by Avrami's law.Comment: Computer Simulation Studies in Condensed Matter Physics XVIII, edited by D.P. Landau, S.P. Lewis, and H.-B. Schuttler, (Springer, Heidelberg, Berlin, in press