1,779 research outputs found
Bosonic sector of D=11 superstring action and the critical dimension. Toy model
Bosonic model inspired by D=11 superstring action is investigated. An
appropriate set of variables is find, in which the light-cone quantization
turns out to be possible. It is shown that anomaly terms in the algebra of the
light-cone Poincare generators are absent for the case D=27.Comment: 8 pages, LaTex file, twic
Polysemy in the mental lexicon: relatedness and frequency affect representational overlap
Meaning relatedness affects storage of ambiguous words in the mental lexicon: unrelated meanings(homonymy) are stored separately whereas related senses (polysemy) are stored as one large representational entry. We hypothesised that word frequency could have similar effects on storage, with low-frequency words having high representational overlap and high-frequency words having low representational overlap. Participants performed lexical decision or semantic
categorisation to high- and low-frequency nouns with few and many senses. Results showed a three-way interaction between frequency, task type, and polysemy. Low-frequency words showed a polysemy advantage with lexical decision but a polysemy disadvantage with semantic categorisation, whereas high-frequency words showed the opposite pattern. These results confirmed our hypothesis that relatedness and word frequency have similar effects on storage of ambiguous words
One-loop vacuum amplitude for D-branes in constant electromagnetic field
Following Polchinski's approach we calculate the one-loop vacuum amplitude
for two parallel D-branes connected by open bosonic (neutral or charged)string
in a constant uniform electromagnetic (EM) field. For neutral string, external
EM field contribution appears as multiplier (Born-Infeld type action) of vacuum
amplitude without external EM field. Hence,it gives the alternative way to see
the inducing of Born-Infeld type action for description of D-branes. For
charged string the situation is more complicated, it may indicate the necessity
to modify the induced D-branes action in this case.Comment: Latex file, 9page
One-loop four-graviton amplitude in eleven-dimensional supergravity
We find explicit expression for the one-loop four-graviton amplitude in
eleven-dimensional supergravity compactified on a circle. Represented in terms
of the string coupling (related to the compactification radius) it takes the
form of an infinite sum of perturbative string loop corrections. We also
compute the amplitude in the case of compactification on a 2-torus which is
given by an SL(2,Z) invariant expansion in powers of the torus area. We discuss
the structure of quantum corrections in eleven-dimensional theory and their
relation to string theory.Comment: 14 pages, harvmac. Remarks on the amplitude in uncompactified D=11
space and on explicit structure of R^4 terms adde
On the discourse of construction competitiveness
It is contended that competitiveness is better understood as a discourse rather than as a characteristic that is supposedly possessed. The discourse of competitiveness derives its legitimacy from the enterprise culture that came to dominance during the 1980s. Current popularized theories of competitiveness are constituent parts of this broader discourse, which has had significant material implications for the UK construction sector. The dominant discourse of competitiveness amongst contracting firms is shaped by the need to achieve structural flexibility to cope with fluctuations in demand. Fashionable espoused improvement recipes such as total quality management, business process re-engineering, and lean construction legitimize and reinforce the material manifestations of the enterprise culture. In consequence, the UK industry is characterized by a plethora of hollowed-out firms that have failed to invest in their human capital. While the adopted model may be rational for individual firms, the systemic effect across the sector as a whole equates to a form of anorexia. However, the discourse of competitiveness is by no means monolithic and continues to be contested locally. There have also been numerous counter-discourses that have been mobilized in response to the undesirable externalities of unbridled enterprise. Currently, important counter-discourses promote the ideas of sustainability and corporate social responsibility
Supersymmetric D3 brane action in AdS_5 x S^5
We find the space-time supersymmetric and kappa-invariant action for a
D3-brane propagating in the AdS_5 x S^5 background. As in the previous
construction of the fundamental string action in this maximally supersymmetric
string vacuum the starting point is the corresponding superalgebra su(2,2|4).
We comment on the super Yang-Mills interpretation of the gauge-fixed form of
the action.Comment: 12 pages, latex. v2: misprints corrected, useful representation of
the WZ part of the action added in section
Type IIB superstring action in AdS_5 x S^5 background
We construct the covariant kappa-symmetric superstring action for a type IIB
superstring on AdS_5 x S^5 background. The action is defined as a 2d
sigma-model on the coset superspace SU(2,2|4) / SO(4,1) x SO(5) and is shown to
be the unique one that has the correct bosonic and flat space limits.Comment: 18 pages, latex. v2: Minor corrections, extended comment on conformal
invariance of the 2d theory; v3,v4: Few signs correcte
The Green--Schwarz Superstring in Extended Configuration Space and Infinitely Reducible First Class Constraints Problem
The Green--Schwarz superstring action is modified to include some set of
additional (on-shell trivial) variables. A complete constraints system of the
theory turns out to be reducible both in the original and in additional
variable sectors. The initial first class constraints and second
class ones are shown to be unified with first and second class
constraints from the additional variables sector, resulting with
-covariant and linearly independent constraint sets. Residual
reducibility proves to fall on second class constraints only.Comment: 14 pages, LaTe
Resonant production of fermions in an axial background
We consider the resonant production of fermions from an oscillating axial
background. The classical evolution of the axial field is given by that of a
massive pseudovector field, as suggested by the renormalizability of the
theory. We look upon both the massive and the massless fermion production from
a perturbative point of view. We obtain the corresponding spectrum and angular
distributions for the different spins or helicities in the particular case of a
spatial-like axial field. We also extend our study to the non-perturbative
regime in the massless case and compare the results with the perturbative ones.Comment: 16 pages, LaTeX, 12 figures; new comments and references added,
version to appear in Phys. Rev.
On SO(32) heterotic - type I superstring duality in ten dimensions
We provide some additional evidence in favour of the strong - weak coupling
duality between the SO(32) heterotic and type I superstring theories by
comparing terms quartic in the gauge field strength in their low-energy
effective actions. We argue that these terms should not receive higher-loop
string corrections so that duality should relate the leading-order perturbative
coefficients in the two theories. In particular, we demonstrate that the
coefficient of the -term in the one-loop (torus) part of the SO(32)
heterotic string action is exactly the same as the coefficient of the
-term in the tree-level (disc) part of the type I action.Comment: 11 pages, harvmac. Several comments added, final version to appear in
Physics Letters
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