Vacuum tunneling in gravity

Topologically non-trivial vacuum structure in gravity models with Cartan variables (vielbein and contortion) is considered. We study the possibility of vacuum space-time tunneling in Einstein gravity assuming that the vielbein may play a fundamental role in quantum gravitational phenomena. It has been shown that in the case of RP3 space topology the tunneling between non-trivial topological vacuums can be realized by means of Eguchi-Hanson gravitational instanton. In Riemann-Cartan geometric approach to quantum gravity the vacuum tunneling can be provided by means of contortion quantum fluctuations. We define double self-duality condition for the contortion and give explicit self-dual configurations which can contribute to vacuum tunneling amplitude.Comment: 11 pages, 1 fig. is added, final versio

Cho and Pak reply to Lamm et al. comment on "A Convergent Series for the QED Effective Action"

Cho and Pak reply to Lamm et al. [hep-th/0007108] comment on "A Convergent Series for the Effective Action of QED" [hep-th/0006057].Comment: 1 pag

Monopoles and Knots in Skyrme Theory

We show that the Skyrme theory actually is a theory of monopoles which allows a new type of solitons, the topological knots made of monopole-anti-monopole pair,which is different from the well-known skyrmions. Furthermore, we derive a generalized Skyrme action from the Yang-Mills action of QCD, which we propose to be an effective action of QCD in the infra-red limit. We discuss the physical implications of our results.Comment: 4 pages. Phys. Rev. Lett. in pres

Color Reflection Invariance and Monopole Condensation in QCD

We review the quantum instability of the Savvidy-Nielsen-Olesen (SNO) vacuum of the one-loop effective action of SU(2) QCD, and point out a critical defect in the calculation of the functional determinant of the gluon loop in the SNO effective action. We prove that the gauge invariance, in particular the color reflection invariance, exclude the unstable tachyonic modes from the gluon loop integral. This guarantees the stability of the magnetic condensation in QCD.Comment: 28 pages, 3 figures, JHEP styl

Simultaneously imaging of dielectric properties and topography in a PbTiO_3 crystal by near-field scanning microwave microscopy

We use a near-field scanning microwave microscope to simultaneously image the dielectric constant, loss tangent, and topography in a PbTiO_3 crystal. By this method, we study the effects of the local dielectric constant and loss tangent in the geometry of periodic domains on the measured resonant frequency, and quality factor. We also carry out theoretical calculations and the results agree well with the experimental data and reveal the anisotropic nature of dielectric constant