1,152 research outputs found
N=2 Superstrings with (1,2m) Spacetime Signature
We show that the superstring in real dimensions, with
criticality achieved by including background charges in the two real time
directions, exhibits a ``coordinate-freezing'' phenomenon, whereby the momentum
in one of the two time directions is constrained to take a specific value for
each physical state. This effectively removes this time direction as a physical
coordinate, leaving the theory with real spacetime signature. Norm
calculations for low-lying physical states suggest that the theory is ghost
free.Comment: 8 page
The Impacts of Information Privacy, Monetary Reward, and Buyersâ Protection Excess on Consumersâ Utility Using E-payment Gateways: A Conjoint Analysis
This paper reports our findings on the impacts of information privacy, financial reward, and buyersâ protection excess on consumersâ utility using E-payment Gateways. We invited users of the G2C E-government Portal of Hong Kong to participate in an online experiment and collected data from 1,795 subjects. From our conjoint analysis, we find that monetary reward has the most significant impact on consumersâ utility among the six design attributes of E-payment Gateways investigated in this study, i.e. monetary reward, online transfer of information, acceptability, buyersâ protection excess, anonymity, and physical control. We also observe that there is a gender impact on the relative importance of these attributes
Anomaly Freedom and Realisations for Super- Strings
We construct new multi-field realisations of the super- algebra,
which are important for building super- string theories. We derive the
structure of the ghost vacuum for such theories, and use the result to
calculate the intercepts. These results determine the conditions for physical
states in the super- string theory.Comment: 22 page
The Complete Spectrum of the String
We obtain the complete physical spectrum of the string, for arbitrary
. The constraints freeze coordinates, while the remaining
coordinates appear in the currents only {\it via} their energy-momentum tensor.
The spectrum is then effectively described by a set of ordinary Virasoro-like
string theories, but with a non-critical value for the central charge and a
discrete set of non-standard values for the spin-2 intercepts. In particular,
the physical spectrum of the string includes the usual massless states of
the Virasoro string. By looking at the norms of low-lying states, we find
strong indications that all the strings are unitary.Comment: 28 page
Embedding of the Bosonic String into the String
We investigate new realisations of the algebra with arbitrary central
charge, making use of the fact that this algebra can be linearised by the
inclusion of a spin-1 current. We use the new realisations with and
to build non-critical and critical BRST operators. Both of these
can be converted by local canonical transformations into a BRST operator for
the Virasoro string with , together with a Kugo-Ojima topological term.
Consequently, these new realisations provide embeddings of the Virasoro string
into non-critical and critical strings.Comment: 11 pages. (Some referencing changes
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Effects of free surface and heterogeneous residual internal stress on stress-driven grain growth in nanocrystalline metals
By reevaluating the experimental study of Zhang et al. (2005), here we demonstrate that the extent of grain growth, previously proposed to be solely driven by external stress, may have been significantly overestimated. A new physical mechanism, termed as free surface assisted stress-driven grain growth (or self-mechanical annealing), is proposed and discussed in detail. Representing the cooperative effect of free surface and heterogeneous residual internal stress, the proposed mechanism is considered more favorable than the traditional pure stress-driven mechanism for interpreting the abnormal grain growth widely observed in deforming nanocrystalline metals at room temperature
Analytic doubly periodic wave patterns for the integrable discrete nonlinear Schroedinger (Ablowitz-Ladik) model
We derive two new solutions in terms of elliptic functions, one for the dark
and one for the bright soliton regime, for the semi-discrete cubic nonlinear
Schroedinger equation of Ablowitz and Ladik. When considered in the complex
plane, these two solutions are identical. In the continuum limit, they reduce
to known elliptic function solutions. In the long wave limit, the dark one
reduces to the collision of two discrete dark solitons, and the bright one to a
discrete breather.Comment: 12 pages, 2 figures. To appear, Physics Letters
Simultaneous saccharification and fermentation of steam exploded duckweed: Improvement of the ethanol yield by increasing yeast titre
This study investigated the conversion of Lemna minor biomass to bioethanol. The biomass was pre-treated by steam explosion (SE, 210 °C, 10 min) and then subjected to simultaneous saccharification and fermentation (SSF) using CellicĂ CTec 2 (20 U or 0.87 FPU gï°1 substrate) cellulase plus b-glucosidase (2 U gï°1 substrate) and a yeast inoculum of 10% (v/v or 8.0 ï° 107 cells mLï°1). At a substrate concentration of 1% (w/v) an ethanol yield of 80% (w/w, theoretical) was achieved. However at a substrate concentration of 20% (w/v), the ethanol yield was lowered to 18.8% (w/w, theoretical). Yields were considerably improved by increasing the yeast titre in the inoculum or preconditioning the yeast on steam exploded liquor. These approaches enhanced the ethanol yield up to 70% (w/w, theoretical) at a substrate concen- tration of 20% (w/v) by metabolising fermentation inhibitors
Non-Markovian dynamics for an open two-level system without rotating wave approximation: Indivisibility versus backflow of information
By use of the two measures presented recently, the indivisibility and the
backflow of information, we study the non-Markovianity of the dynamics for a
two-level system interacting with a zero-temperature structured environment
without using rotating wave approximation (RWA). In the limit of weak coupling
between the system and the reservoir, and by expanding the time-convolutionless
(TCL) generator to the forth order with respect to the coupling strength, the
time-local non-Markovian master equation for the reduced state of the system is
derived. Under the secular approximation, the exact analytic solution is
obtained and the sufficient and necessary conditions for the indivisibility and
the backflow of information for the system dynamics are presented. In the more
general case, we investigate numerically the properties of the two measures for
the case of Lorentzian reservoir. Our results show the importance of the
counter-rotating terms to the short-time-scale non-Markovian behavior of the
system dynamics, further expose the relations between the two measures and
their rationality as non-Markovian measures. Finally, the complete positivity
of the dynamics of the considered system is discussed
Stabilization and pumping of giant vortices in dilute Bose-Einstein condensates
Recently, it was shown that giant vortices with arbitrarily large quantum
numbers can possibly be created in dilute Bose-Einstein condensates by
cyclically pumping vorticity into the condensate. However, multiply quantized
vortices are typically dynamically unstable in harmonically trapped nonrotated
condensates, which poses a serious challenge to the vortex pump procedure. In
this theoretical study, we investigate how the giant vortices can be stabilized
by the application of a Gaussian potential peak along the vortex core. We find
that achieving dynamical stability is feasible up to high quantum numbers. To
demonstrate the efficiency of the stabilization method, we simulate the
adiabatic creation of an unsplit 20-quantum vortex with the vortex pump.Comment: 8 pages, 6 figures; to be published in J. Low Temp. Phys., online
publication available at http://dx.doi.org/10.1007/s10909-010-0216-
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