73,052 research outputs found
Probing the SUSY breaking scale at an collider
If supersymmetry is spontaneously at a low energy scale then the resulting
gravitino would be very light. The interaction strength of the longitudinal
components of such a light gravitino to electron-selectron pair then becomes
comparable to that of electroweak interactions. Such a light gravitino could
modify the cross-section for e^_L e^_R-->\tilde {e}_L\tilde {e}_R from its
MSSM value. Precision measurement of this cross-section could therefore be used
to probe the low energy SUSY breaking scale.Comment: Plain Tex, 7 pages, No figure
Total energy differences between SiC polytypes revisited
The total energy differences between various SiC polytypes (3C, 6H, 4H, 2H,
15R and 9R) were calculated using the full-potential linear muffin-tin orbital
method using the Perdew-Wang-(91) generalized gradient approximation to the
exchange-correlation functional in the density functional method. Numerical
convergence versus k-point sampling and basis set completeness are demonstrated
to be better than 1 meV/atom. The parameters of several generalized anisotropic
next-nearest-neighbor Ising models are extracted and their significance and
consequences for epitaxial growth are discussed.Comment: 8 pages, 3 figures, Latex, uses epsfig and revte
Quantum Isometrodynamics
Classical Isometrodynamics is quantized in the Euclidean plus axial gauge.
The quantization is then generalized to a broad class of gauges and the
generating functional for the Green functions of Quantum Isometrodynamics (QID)
is derived. Feynman rules in covariant Euclidean gauges are determined and QID
is shown to be renormalizable by power counting. Asymptotic states are
discussed and new quantum numbers related to the "inner" degrees of freedom
introduced. The one-loop effective action in a Euclidean background gauge is
formally calculated and shown to be finite and gauge-invariant after
renormalization and a consistent definition of the arising "inner" space
momentum integrals. Pure QID is shown to be asymptotically free for all
dimensions of "inner" space whereas QID coupled to the Standard Model
fields is not asymptotically free for D <= 7. Finally nilpotent BRST
transformations for Isometrodynamics are derived along with the BRST symmetry
of the theory and a scetch of the general proof of renormalizability for QID is
given.Comment: 38 page
A Study on the Noise Threshold of Fault-tolerant Quantum Error Correction
Quantum circuits implementing fault-tolerant quantum error correction (QEC)
for the three qubit bit-flip code and five-qubit code are studied. To describe
the effect of noise, we apply a model based on a generalized effective
Hamiltonian where the system-environment interactions are taken into account by
including stochastic fluctuating terms in the system Hamiltonian. This noise
model enables us to investigate the effect of noise in quantum circuits under
realistic device conditions and avoid strong assumptions such as maximal
parallelism and weak storage errors. Noise thresholds of the QEC codes are
calculated. In addition, the effects of imprecision in projective measurements,
collective bath, fault-tolerant repetition protocols, and level of parallelism
in circuit constructions on the threshold values are also studied with emphasis
on determining the optimal design for the fault-tolerant QEC circuit. These
results provide insights into the fault-tolerant QEC process as well as useful
information for designing the optimal fault-tolerant QEC circuit for particular
physical implementation of quantum computer.Comment: 9 pages, 9 figures; to be submitted to Phys. Rev.
Comment on ``Majoron emitting neutrinoless double beta decay in the electroweak chiral gauge extensions''
We point out that if the majoron-like scheme is implemented within a 331
model, there must exist at least three different mass scales for the scalar
vacuum expectation values in the model.Comment: 4 pages, no figures, Revtex. To be published in Physical Review
Limits on Ï„ lepton-flavor violating decays into three charged leptons
A search for the neutrinoless, lepton-flavor violating decay of the τ lepton into three charged leptons has been performed using an integrated luminosity of 468  fb^(-1) collected with the BABAR detector at the PEP-II collider. In all six decay modes considered, the numbers of events found in data are compatible with the background expectations. Upper limits on the branching fractions are set in the range (1.8–3.3)×10^(-8) at 90% confidence level
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