7,936 research outputs found
Some Recent Developments in Sphalerons
We review briefly the sphaleron and list some of its properties. We summarize
some of the results in models which have an extended scalar sector. We also
present our work on models dealing with physics beyond the standard model. We
focus on the energy of the sphaleron which is important in determining the rate
of baryon number violation at the electroweak scale.Comment: Tex, 5 pages (one figure available by request), to appear in
Proceedings of Beyond the Standard Model IV, Lake Tahoe, CA, Dec. 199
Some Phenomenology of the top quark with non-standard couplings
In this talk I will use effective lagrangian and discuss possible new physics
associated with top quark.Comment: 5 pages, Latex, figures available by reques
Weaving independently generated photons into an arbitrary graph state
The controlled Z (CZ) operations acting separately on pairs of qubits are
commonly adopted in the schemes of generating graph states, the multi-partite
entangled states for the one-way quantum computing. For this purpose, we
propose a setup of cascade CZ operation on a whole group of qubits in sequence.
The operation of the setup starts with entangling an ancilla photon to the
first photon as qubit, and this ancilla automatically moves from one
entanglement link to another in assisting the formation of a string in graph
states. The generation of some special types of graph states, such as the
three-dimensional ones, can be greatly simplified in this approach. The setup
presented uses weak nonlinearities, but an implementation using probabilistic
linear optics is also possible.Comment: 6 pages, 7 figures. Accepted by Phys. Rev.
Highly Efficient Processing Multi-photon States
How to implement multi-qubit gates is an important problem in quantum
information processing. Based on cross phase modulation, we present an approach
to realizing a family of multi-qubit gates that deterministically operate on
single photons as the qubits. A general -qubit unitary operation is a
typical example of these gates. The approach greatly relax the requirement on
the resources, such as the ancilla photons and coherent beams, as well as the
number of operations on the qubits. The improvement in this framework may
facilitate large scale quantum information processing.Comment: to be published in Scientific Reports. 14 pages, 5 figures (plus 5
pages and 2 figures in supplementary materials
A Framework for Extracting Semantic Guarantees from Privacy
Statistical privacy views privacy definitions as contracts that guide the
behavior of algorithms that take in sensitive data and produce sanitized data.
For most existing privacy definitions, it is not clear what they actually
guarantee.
In this paper, we propose the first (to the best of our knowledge) framework
for extracting semantic guarantees from privacy definitions. That is, instead
of answering narrow questions such as "does privacy definition Y protect X?"
the goal is to answer the more general question "what does privacy definition Y
protect?"
The privacy guarantees we can extract are Bayesian in nature and deal with
changes in an attacker's beliefs. The key to our framework is an object we call
the row cone. Every privacy definition has a row cone, which is a convex set
that describes all the ways an attacker's prior beliefs can be turned into
posterior beliefs after observing an output of an algorithm satisfying that
privacy definition.
The framework can be applied to privacy definitions or even to individual
algorithms to identify the types of inferences they defend against. We
illustrate the use of our framework with analyses of several definitions and
algorithms for which we can derive previously unknown semantics. These include
randomized response, FRAPP, and several algorithms that add integer-valued
noise to their inputs
A groupoidification of the fermion algebra
In this paper, we consider the groupoidification of the fermion algebra. We
construct a groupoid as the categorical analogues of the fermionic Fock space,
and the creation and annihilation operators correspond to spans of groupoids.
The categorical fermionic Fock states have some extra structures comparing with
the normal forms. We also construct a 2-category of spans of groupoids
corresponding to the fermion algebra. The relations of the morphisms in this
2-category are consistent with those in the graphical category which is
represented by string diagrams.Comment: 10 pages, tikz diagram
Electroweak Sphaleron in Large Higgs Boson Mass Limit
Since the TRIVIALITY argument of the Higgs sector requires the existence of
new physics beyond the standard model, there should exist a cutoff
beyond which the standard model will breakdown. The cutoff can be determined
from the position of the Landau pole. We study the effects of this cutoff on
the energy of the electroweak sphaleron, , in the large Higgs boson
mass limit. We found that becomes arbitrarily large as the Higgs
boson mass increases. This is in contrast to the well-known result, which is
held in the standard model and a wide class of its extensions, that
is stable against the variation of the {\it bare} Higgs boson mass. The
physical meaning of this result is discussed.Comment: Iowa State University Preprint, IS-J 5268, December 1993, 10 Pages,
(TeX file
Edge Stability of BN sheets and Its Application for Designing Hybrid BNC Structures
First-principles investigations on the edge energies and edge stresses of
single-layer hexagonal boron-nitride (BN) are presented. The armchair edges of
BN nanoribbons (BNNRs) are more stable in energy than zigzag ones. Armchair
BNNRs are under compressive edge stress while zigzag BNNRs are under tensile
edge stress. The intrinsic spin-polarization and edge saturation play important
roles in modulating the edge stability of BNNRs. The edge energy difference
between BN and graphene could be used to guide the design of the specific
hybrid BNC structures: in an armchair BNC nanoribbon (BNCNR), BN domains are
expected to grow outside of C domains, while the opposite occurs in a zigzag
BNCNR. More importantly, armchair BNCNRs can reproduce unique electronic
properties of armchair graphene nanoribbons (GNRs), which are expected to be
robust against edge functionalization or disorder. Within certain C/BN ratio,
zigzag BNCNRs may exhibit intrinsic half-metallicity without any external
constraints. These unexpected electronic properties of BNCNRs may offer unique
opportunities to develop nanoscale electronics and spintronics beyond
individual graphene and BN. Generally, these principles for designing BNC could
be extended to other hybrid nanostructures.Comment: 6 figure
Suppression of spin-polarization in graphene nanoribbon by edge defect and impurity
We investigate the effect of edge defects (vacancies) and impurities
(substitutional dopants) on the robustness of spin-polarization in graphene
nanoribbons (GNRs) with zigzag edges, using density-functional-theory
calculations. We found that the stability of the spin state and its magnetic
moments decrease continuously with increasing concentration of defects or
impurities. The system generally becomes non-magnetic at the concentration of
one edge defect (impurity) per 10 angstrom. The spin suppression is shown to be
caused by reduction and removal of edge states at the Fermi energy. Our
analysis implies an important criterion on the GNR samples for spintronics
applications.Comment: 10 pages, 5 figure
Breaking optomechanical cooling limit by two drive fields on a membrane-in-middle system
We present a theoretical scheme for ground state cooling of a mechanical
resonator in a membrane-in-middle optomechanical system (OMS) driven by two
red-detuned drive fields. The details of dynamical evolution of OMS are
provided, and the effect of system conditions on cooling results are
systematically studied. Most importantly, the setups with two drives are found
to be capable of achieving better cooling results than the theoretical cooling
limit with single cavity. Even an improvement by one order of thermal phonon
number is possible with proper combination of the cavity damping rate and drive
intensity.Comment: 10 pages, 6 figures, accepted by Physical Review
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