9,049 research outputs found
Normal ordering and boundary conditions for fermionic string coordinates
We build up normal ordered products for fermionic open string coordinates
consistent with boundary conditions. The results are obtained considering the
presence of antisymmetric tensor fields. We find a discontinuity of the normal
ordered products at string endpoints even in the absence of the background. We
discuss how the energy momentum tensor also changes at the world-sheet boundary
in such a way that the central charge keeps the standard value at string end
points.Comment: In this revised version we clarify the issue of consistency between
supersymmetry and boundary conditions and stress the fact that we are
considering flat space. we also add two more reference
Normal ordering and boundary conditions in open bosonic strings
Boundary conditions play a non trivial role in string theory. For instance
the rich structure of D-branes is generated by choosing appropriate
combinations of Dirichlet and Neumann boundary conditions. Furthermore, when an
antisymmetric background is present at the string end-points (corresponding to
mixed boundary conditions) space time becomes non-commutative there.
We show here how to build up normal ordered products for bosonic string
position operators that satisfy both equations of motion and open string
boundary conditions at quantum level. We also calculate the equal time
commutator of these normal ordered products in the presence of antisymmetric
tensor background.Comment: 7 pages no figures, References adde
¿Ingresan los alumnos a la Universidad con un adecuado desarrollo de los niveles de razonamiento?
Characterization of the CBC2 readout ASIC for the CMS strip-tracker high-luminosity upgrade
The CMS Binary Chip 2 (CBC2) is a full-scale prototype ASIC developed for the front-end readout of the high-luminosity upgrade of the CMS silicon strip tracker. The 254-channel, 130 nm CMOS ASIC is designed for the binary readout of double-layer modules, and features cluster-width discrimination and coincidence logic for detecting high-PT track candidates. The chip was delivered in January 2013 and has since been bump-bonded to a dual-chip hybrid and extensively tested. The CBC2 is fully functional and working to specification: we present the result of electrical characterization of the chip, including gain, noise, threshold scan and power consumption, together with the performance of the stub finding logic. Finally we will outline the plan for future developments towards the production version
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