Nonconservation of global quantum numbers in RS-type models

作者:Tibor Torma 刊名: 上传者:段忠宝

【摘要】In Randall-Sundrum type scenarios the effective size of the extra dimension remains unconstrained. A TeV-scale brane tension without orbifold boundary conditions would allow phenomenologically observable processes at high energy colliders. Among others; the brane could fragment into bubbles that fly away for good or return within a time ≤ O(1mm)/c. Particles trapped on the bubbles may fake nonconservation of global or electric charges. In this letter we explore the generic (model independent) features of these bubbles. We describe the brane dynamics by a scalar field coupled derivatively to the energy momentum tensor by dimension-8 operators. Mass is generated to this field by any brane stabilization mechanism. The bubbles may be stabilized by the Casimir effect. When the threshold energy of √ s ~ brane tension ≥ TeV is reached; bubbles with TeV ?1 size are copiously produced. At lower √ s; smaller bubbles can be produced (if they exist) with strongly suppressed probability. Our world may be a 4-dimensional flat submanifold of a strongly curved 5-dimensional spacetime [1–3]. One such scenario [1] may explain the gauge hierarchy problem when the 5-dimensional curvature radius is at the Planck scale and spacetime is a thin “sandwich” between two 4-dimensional surfaces. The surfaces may be stabilized at a distance somewhat exceeding the Planck length by supposing scalar fields in the “bulk” and proper type of interactions [4]. Alternatively [2]; an infinite sized fifth dimension is also conceivable with effectively 4-dimensional gravity on one “brane”. The bulk is a slice ofAdS5 with only gravity living there; with a negative cosmological constant Λ5. The brane is stabilized by requiring that the metric is symmetric (“orbifold symmetry”) in the fifth coordinate. The flatness our world is ensured by the (extreme) fine tuning of the tension of the brane Λ4 = 12kM 3 5 ; where M5 is the 5-dimensional Planck mass and k ?1 = ( ?Λ5 12M 5 )?1/2 is the AdS length. The resulting strength of the 4-dimensional effective gravity comes out to be M4 = (M 3 5 /k) ; identified with the Planck mass 10GeV . In these models the hierarchy problem is not addressed; though. Another version of the same set of ideas appeared in [3]; where it is shown that a world confined to a third brane with small positive tension located inside the