3,999 research outputs found
Pretender punishment induced by chemical signalling in a queenless ant
Animal societies are stages for both conflict and cooperation. Reproduction is often monopolized by one or a few individuals who behave aggressively to prevent subordinates from reproducing (for example, naked mole-rats, wasps and ants). Here we report an unusual mechanism by which the dominant individual maintains reproductive control. In the queenless ant Dinoponera quadriceps, only the alpha female reproduces. If the alpha is challenged by another female she chemically marks the pretender who is then punished by low-ranking females. This cooperation between alpha and low-rankers allows the alpha to inflict punishment indirectly, thereby maintaining her reproductive primacy without having to figh
Quantum Link Models with Many Rishon Flavors and with Many Colors
Quantum link models are a novel formulation of gauge theories in terms of
discrete degrees of freedom. These degrees of freedom are described by quantum
operators acting in a finite-dimensional Hilbert space. We show that for
certain representations of the operator algebra, the usual Yang-Mills action is
recovered in the continuum limit. The quantum operators can be expressed as
bilinears of fermionic creation and annihilation operators called rishons.
Using the rishon representation the quantum link Hamiltonian can be expressed
entirely in terms of color-neutral operators. This allows us to study the large
N_c limit of this model. In the 't Hooft limit we find an area law for the
Wilson loop and a mass gap. Furthermore, the strong coupling expansion is a
topological expansion in which graphs with handles and boundaries are
suppressed.Comment: Lattice2001(theorydevelop), poster by O. Baer and talk by B.
Schlittgen, 6 page
Capitalism and natural rights: Marx, Locke and the moral justification of capitalism: inaugural lecture delivered at Rhodes University
Inaugural lecture delivered at Rhodes UniversityRhodes University Libraries (Digitisation)ONE of the commonplaces among political philosophers and theorists is the contempt with which Marx regarded Natural Rights theory. In 1843 he wrote that "the so-called rights of man, the droit de l'homme as distinct from the droit du citoyen, are nothing but the rights of a member of civil society, that is the rights of egoistic man, of man separated from other men and from the community." And again "the real man is recognised only in the shape of the egoistic individual, the true man is recognised only in the shape of the abstract citoyen."1 Marx saw Natural Rights as means for the justification of capitalism, and so, as justifying inequalities of wealth and property-ownership. And of course it is true that many writers, in supporting Natural Rights, have stressed, as Stuart Brown expresses it, that "They are the rights of a man to the protection of what is in his interest. The moral interests of one man may differ radically from those of another. Different men may have radically different needs and capacities. And these differences, in conjunction with unavoidable differences in opportunity, produce differences in estate. "2 Expressions of this kind make clear the point of Marx's critique. I wish tonight to argue and to attempt to establish two main theses. The first is that, despite Marx's expressed attitudes to Natural Rights, his own theory of capitalism cannot easily be disentangled from Natural Rights theory, and, if my argument is right, it in fact depends upon it. Secondly, I shall try to show, through an examination of the theories of John Locke, that if Natural Rights theory is to be taken seriously, it is at odds with the very capitalist theory which it is generally taken to support, and that Natural Rights cannot therefore provide an adequate under-pinning of capitalism, at least not without generating self-contradictions within the theory of Natural Rights. If the arguments which I shall present are right, I shall hope to have established what might be termed two paradoxes
Astrophysical S-factors for fusion reactions involving C, O, Ne and Mg isotopes
Using the Sao Paulo potential and the barrier penetration formalism we have
calculated the astrophysical factor S(E) for 946 fusion reactions involving
stable and neutron-rich isotopes of C, O, Ne, and Mg for center-of-mass
energies E varying from 2 MeV to 18-30 MeV (covering the range below and above
the Coulomb barrier). We have parameterized the energy dependence S(E) by an
accurate universal 9-parameter analytic expression and present tables of fit
parameters for all the reactions. We also discuss the reduced 3-parameter
version of our fit which is highly accurate at energies below the Coulomb
barrier, and outline the procedure for calculating the reaction rates. The
results can be easily converted to thermonuclear or pycnonuclear reaction rates
to simulate various nuclear burning phenomena, in particular, stellar burning
at high temperatures and nucleosynthesis in high density environments.Comment: 30 pages including 11 tables, 4 figures, ADNDT, accepte
QCD as a Quantum Link Model
QCD is constructed as a lattice gauge theory in which the elements of the
link matrices are represented by non-commuting operators acting in a Hilbert
space. The resulting quantum link model for QCD is formulated with a fifth
Euclidean dimension, whose extent resembles the inverse gauge coupling of the
resulting four-dimensional theory after dimensional reduction. The inclusion of
quarks is natural in Shamir's variant of Kaplan's fermion method, which does
not require fine-tuning to approach the chiral limit. A rishon representation
in terms of fermionic constituents of the gluons is derived and the quantum
link Hamiltonian for QCD with a U(N) gauge symmetry is expressed in terms of
glueball, meson and constituent quark operators. The new formulation of QCD is
promising both from an analytic and from a computational point of view.Comment: 27 pages, including three figures. ordinary LaTeX; Submitted to Nucl.
Phys.
QUANTIFYING THE COST OF SUBSTANDARD PATENTS: SOME PRELIMINARY EVIDENCE
The purpose of patent policy is to balance the incentive to invent against the ability of the economy to utilize and incorporate new inventions and innovations. Substandard patents that upset this balance impose deadweight losses and other costs on the economy. In this paper, we examine some of the deadweight losses that result from granting substandard patents in the United States. Under plausible assumptions, we find that the economic losses resulting from the grant of substandard patents can reach 4.5 billion annually. This brings the total deadweight loss created by our dented patent system to be at least $25.5 billion annually. These estimates may be viewed as conservative because they do not take into account other economic costs from our existing patent system, such as the consumer welfare losses from granting monopoly rents to patent holders that have not, in the end, invented a novel product, or the full social value of the innovations lost
A quantum Monte Carlo algorithm realizing an intrinsic relaxation
We propose a new quantum Monte Carlo algorithm which realizes a relaxation
intrinsic to the original quantum system. The Monte Carlo dynamics satisfies
the dynamic scaling relation and is independent of the Trotter
number. Finiteness of the Trotter number just appears as the finite-size
effect. An infinite Trotter number version of the algorithm is also formulated,
which enables us to observe a true relaxation of the original system. The
strategy of the algorithm is a compromise between the conventional worldline
local flip and the modern cluster loop flip. It is a local flip in the
real-space direction and is a cluster flip in the Trotter direction. The new
algorithm is tested by the transverse-field Ising model in two dimensions. An
accurate phase diagram is obtained.Comment: 9 pages, 4 figure
Ultrafast supercontinuum spectroscopy of carrier multiplication and biexcitonic effects in excited states of PbS quantum dots
We examine the multiple exciton population dynamics in PbS quantum dots by
ultrafast spectrally-resolved supercontinuum transient absorption (SC-TA). We
simultaneously probe the first three excitonic transitions over a broad
spectral range. Transient spectra show the presence of first order bleach of
absorption for the 1S_h-1S_e transition and second order bleach along with
photoinduced absorption band for 1P_h-1P_e transition. We also report evidence
of the one-photon forbidden 1S_{h,e}-1P_{h,e} transition. We examine signatures
of carrier multiplication (multiexcitons for the single absorbed photon) from
analysis of the first and second order bleaches, in the limit of low absorbed
photon numbers (~ 10^-2), at pump energies from two to four times the
semiconductor band gap. The multiexciton generation efficiency is discussed
both in terms of a broadband global fit and the ratio between early- to
long-time transient absorption signals.. Analysis of population dynamics shows
that the bleach peak due to the biexciton population is red-shifted respect the
single exciton one, indicating a positive binding energy.Comment: 16 pages, 5 figure
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