Biomolecular sensing using surface micromachined silicon plates

Micromachined sensors to detect surface stress changes associated with interactions between an immobilized chemically selective receptor and a target analyte are presented. The top isolated sensing surface of a free-standing silicon plate is prepared with a thin Au layer, followed by a covalent attachment of chemical or biomolecule forming a chemically-selective surface. Surface stress changes in air are measured capacitively due to the formation of an alkanethiol self-assembled monolayer (SAM). Detection of biomolecular binding in liquid samples is measured optically using the streptavidin-biotin complex and AM. tuberculosis antigen-antibody system used for clinical tuberculosis (TB) diagnosis

QCD Effective action at high temperature and small chemical potential

We present a construction of an effective Yang-Mills action for QCD, from the expansion of the fermionic determinant in terms of powers of the chemical potential at high temperature, for the case of massless quarks. We analyze this expansion in the perturbative region and find that it gives extra spurious information. We propose for the non-perturbative sector a simplified effective action which, in principle, contains only the relevant information.Comment: 3 pages. To appear in the proceedings of the 7th Conference on Strong & Electroweak Matter (SEWM06), BNL, May 200

Derivative expansion of quadratic operators in a general 't Hooft gauge

A derivative expansion technique is developed to compute functional determinants of quadratic operators, non diagonal in spacetime indices. This kind of operators arise in general 't Hooft gauge fixed Lagrangians. Elaborate applications of the developed derivative expansion are presented.Comment: 40 pages, to appear in Phys. Rev.

Interplay of quark and meson degrees of freedom in a near-threshold resonance

We investigate the interplay of quark and meson degrees of freedom in a physical state representing a near-threshold resonance for the case of a single continuum channel. We demonstrate that such a near-threshold resonance may possess quite peculiar properties if both quark and meson dynamics generate weakly coupled near-threshold poles in the S-matrix. In particular, the scattering t-matrix may possess zeros in this case. We also discuss possible implications for production reactions as well as studies within lattice QCD.Comment: LaTeX2e, 11 pages, minor typo corrections, to appear in Eur.Phys.J.

Massive quantum fields in a conical background

Representations of the Klein-Gordon and Dirac propagators are determined in a $N$ dimensional conical background for massive fields twisted by an arbitrary angle $2\pi\sigma$. The Dirac propagator is shown to be obtained from the Klein-Gordon propagator twisted by angles $2\pi\sigma\pm {\cal D}/2$ where ${\cal D}$ is the cone deficit angle. Vacuum expectation values are determined by a point-splitting method in the proper time representation of the propagators. Analogies with the Aharonov-Bohm effect are pointed out throughout the paper and a conjecture on an extension to fields of arbitrary spin is given.Comment: Propagator (11) is rewritten in a more convenient form and the one before that is amended. A more concise expression is given for the energy density of a twisted spinor. The references contain minor correction

Higher-Spin Theory and Space-Time Metamorphoses

Introductory lectures on higher-spin gauge theory given at 7 Aegean workshop on non-Einstein theories of gravity. The emphasis is on qualitative features of the higher-spin gauge theory and peculiarities of its space-time interpretation. In particular, it is explained that Riemannian geometry cannot play a fundamental role in the higher-spin gauge theory. The higher-spin symmetries are argued to occur at ultra high energy scales beyond the Planck scale. This suggests that the higher-spin gauge theory can help to understand Quantum Gravity. Various types of higher-spin dualities are briefly discussed.Comment: 37 pages, no figures; V2: references adde

Non-perturbative quenched propagator beyond the infrared approximation

A new approach to the quenched propagator in QED beyond the IR limit is proposed. The method is based on evolution equations in the proper time.Comment: 13 pages, 1 figure; Misprint on reference correcte

Nonperturbative late time asymptotics for heat kernel in gravity theory

Recently proposed nonlocal and nonperturbative late time behavior of the heat kernel is generalized to curved spacetimes. Heat kernel trace asymptotics is dominated by two terms one of which represents a trivial covariantization of the flat-space result and another one is given by the Gibbons-Hawking integral over asymptotically-flat infinity. Nonlocal terms of the effective action generated by this asymptotics might underly long- distance modifications of the Einstein theory motivated by the cosmological constant problem. New mechanisms of the cosmological constant induced by infrared effects of matter and graviton loops are briefly discussed.Comment: 22 pages, LaTeX, final version, to be published in Phys. Rev.

Renormalization-Group Improved Effective Potential for Interacting Theories with Several Mass Scales in Curved Spacetime

The renormalization group (RG) is used in order to obtain the RG improved effective potential in curved spacetime. This potential is explicitly calculated for the Yukawa model and for scalar electrodynamics, i.e. theories with several (namely, more than one) mass scales, in a space of constant curvature. Using the $\lambda \varphi^4$-theory on a general curved spacetime as an example, we show how it is possible to find the RG improved effective Lagrangian in curved spacetime. As specific applications, we discuss the possibility of curvature induced phase transitions in the Yukawa model and the effective equations (back-reaction problem) for the $\lambda \varphi^4$-theory on a De Sitter background.Comment: 18 pages, LaTeX file, UB-ECM-PF 93/2

Ultraviolet Complete Quantum Gravity

An ultraviolet complete quantum gravity theory is formulated in which vertex functions in Feynman graphs are entire functions and the propagating graviton is described by a local, causal propagator. The cosmological constant problem is investigated in the context of the ultraviolet complete quantum gravity.Comment: 11 pages, no figures. Changes to text. Results remain the same. References added. To be published in European Physics Journal Plu