2,015 research outputs found
Leading QCD-induced four-loop contributions to the -function of the Higgs self-coupling in the SM and vacuum stability
We present analytical results for the leading top-Yukawa and QCD contribution
to the -function for the Higgs self-coupling of the Standard
Model at four-loop level, namely the part independently
confirming a result given in [1]. We also give the contribution of the anomalous dimension of the Higgs field as well as the terms
to the top-Yukawa -function which can also be
derived from the anomalous dimension of the top quark mass. We compare the
results with the RG functions of the correlators of two and four scalar
currents in pure QCD and find a new relation between the anomalous dimension
of the QCD vacuum energy and the anomalous dimension
appearing in the RG equation of the correlator of two scalar currents. Together
with the recently computed top-Yukawa and QCD contributions to
[2,3] the -functions presented here constitute the leading four-loop
contributions to the evolution of the Higgs self-coupling. A numerical estimate
of these terms at the scale of the top-quark mass is presented as well as an
analysis of the impact on the evolution of up to the Planck scale and
the vacuum stability problem.Comment: v2: This is the version accepted by JHEP; extended discussion of the
numerics and vacuum stability analysis; references added; plot adde
Four-loop renormalization of QCD with a reducible fermion representation of the gauge group: anomalous dimensions and renormalization constants
We present analytical results at four-loop level for the renormalization
constants and anomalous dimensions of an extended QCD model with one coupling
constant and an arbitrary number of fermion representations. One example of
such a model is the QCD plus gluinos sector of a supersymmetric theory where
the gluinos are Majorana fermions in the adjoint representation of the gauge
group.
The renormalization constants of the gauge boson, ghost and fermion fields
are analytically computed as well as those for the ghost-gluon vertex, the
fermion-gluon vertex and the fermion mass. All other renormalization constants
can be derived from these. Some of these results were already produced in
Feynman gauge for the computation of the beta-function of this model, which was
recently published. Here we present results for an arbitrary gauge parameter.Comment: v2: version accepted by JHEP, extended discussion of the treatment of
Majorana spinor
Avenues and incentives for commercial use of a low-gravity environment
The scientific and commercial utilization of the low-g environments for materials research and for process and product development is considered. Any products of commercial interest which necessitate processing in space will probably be low volume, high value items. To encourage the commercialization of materials processing in low-g, NASA, in parallel with establishing and demonstrating the scientific/technological precepts for analyzing and using a low-g environment, is establishing the legal and management mechanisms to share in the cost and risk of early commercial ventures, and is now working with commercial firms on a case-by basis to explore applications of this new technology to specific needs of the company
Commercialization of Materials Processing in Space
The primary motivation of the Materials Processing in Space program is the scientific and commercial utilization of the effects of the unique environments of space on material processes. The reduction or elimination of the pervasive influences of gravity on Earth-based process mechanisms affords opportunities for understanding and improving ground-based processing or producing select materials in space which, typically, would be of low volume, high value commercial interest. Additionally, the unlimited, if not hard vacuum of space affords equally interesting influences on material processes. To evolve the commercialization of Materials Processing in Space, the program seeks to establish and demonstrate the scientific/technological precepts for analyzing and using the space environment and, in parallel, to establish the legal and management mechanisms to implement commercial ventures
Cavity-assisted squeezing of a mechanical oscillator
We investigate the creation of squeezed states of a vibrating membrane or a
movable mirror in an opto-mechanical system. An optical cavity is driven by
squeezed light and couples via radiation pressure to the membrane/mirror,
effectively providing a squeezed heat-bath for the mechanical oscillator. Under
the conditions of laser cooling to the ground state, we find an efficient
transfer of squeezing with roughly 60% of light squeezing conveyed to the
membrane/mirror (on a dB scale). We determine the requirements on the carrier
frequency and the bandwidth of squeezed light. Beyond the conditions of ground
state cooling, we predict mechanical squashing to be observable in current
systems.Comment: 7.1 pages, 3 figures, submitted to PR
Opto-mechanical transducers for long-distance quantum communication
We describe a new scheme to interconvert stationary and photonic qubits which
is based on indirect qubit-light interactions mediated by a mechanical
resonator. This approach does not rely on the specific optical response of the
qubit and thereby enables optical quantum interfaces for a wide range of solid
state spin and charge based systems. We discuss the implementation of quantum
state transfer protocols between distant nodes of a large scale network and
evaluate the effect of the main noise sources on the resulting state transfer
fidelities. For the specific examples of electronic spin qubits and
superconducting charge qubits we show that high fidelity quantum communication
protocols can be implemented under realistic experimental conditions.Comment: Version as accepted by PR
Paper Session I-A - Advanced Solid Rocket Motor (ASRM)
The Advanced Solid Rocket Motor (ASRM) is a150-in. diameter segmented motor design that incorporates substantive design changes to improve the reliability and design safety margins of the space shuttle system. The new motor thrust characteristics are tailored to preclude the necessity for throttling the Space Shuttle Main Engines (SSME) during the period of maximum dynamic pressure. This reduces or eliminates about 175 criticality 1/1R failure modes for the shuttle system. Furthermore, the ASRM is designed to provide a 12,000 Ib payload improvement which will support space station development and other critical NASA missions.
To achieve the level of process control and automation needed for high quality, reproducibility, and improved reliability, NASA concluded that a substantially new modern, fully-automated facility is required. Sites selected to produce and test the ASRM are the TVA Yellow Creek Mississippi site and the Stennis Space Center site, respectively.
The ASRM design/program evolved from Phase A studies conducted in late 1986 and Phase B studies conducted from mid-1987 to April 1988. All major solid propulsion contractors participated in these studies. The study results culminated in the release of an ASRM Request for Proposals (phase C/D) October 31, 1988. Authority to proceed (ATP) with the Development and Verification Program is currently planned for April 1, 1989, with the first ASRM Shuttle development flight tentatively scheduled for late 1994
- …