550 research outputs found
Human Rights and Intellectual Property: Mapping the Global Interface
Human Rights and Intellectual Property: Mapping the Global Interface explores the intersections between intellectual property and human rights law and policy. The relationship between these two fields has captured the attention of governments, policymakers, and activist communities in a diverse array of international and domestic political and judicial venues. These actors often raise human rights arguments as counterweights to the expansion of intellectual property in areas including freedom of expression, public health, education, privacy, agriculture, and the rights of indigenous peoples. At the same time, the creators and owners of intellectual property are asserting a human rights justification for the expansion of legal protections. The book explores the legal, institutional, and political implications of these competing claims in three ways: (1) by offering a framework for exploring the connections and divergences between these subjects; (2) by identifying the pathways along which jurisprudence, policy, and political discourse are likely to evolve; and (3) by serving as a teaching and learning resource for scholars, activists, and students. This excerpt contains the book\u27s table of contents, preface, and concluding chapter
Quantum nature of black holes
I reconsider Hawking's analysis of the effects of gravitational collapse on
quantum fields, taking into account interactions between the fields. The
ultra-high energy vacuum fluctuations, which had been considered to be an
awkward peripheral feature of the analysis, are shown to play a key role. By
interactions, they can scatter particles to, or create pairs of particle at,
ultra-high energies. The energies rapidly become so great that quantum gravity
must play a dominant role. Thus the vicinities of black holes are essentially
quantum-gravitational regimes.Comment: 7 pages, 5 figures. Honorable mention in the 2004 Gravity Research
Foundation Essay Competitio
Moving Mirrors and Thermodynamic Paradoxes
Quantum fields responding to "moving mirrors" have been predicted to give
rise to thermodynamic paradoxes. I show that the assumption in such work that
the mirror can be treated as an external field is invalid: the exotic
energy-transfer effects necessary to the paradoxes are well below the scales at
which the model is credible. For a first-quantized point-particle mirror, it
appears that exotic energy-transfers are lost in the quantum uncertainty in the
mirror's state. An accurate accounting of these energies will require a model
which recognizes the mirror's finite reflectivity, and almost certainly a model
which allows for the excitation of internal mirror modes, that is, a
second-quantized model.Comment: 7 pages, Revtex with Latex2
Red-shifts near black holes
A simple ordinary differential equation is derived governing the red-shifts
of wave-fronts propagating through a non-stationary spherically symmetric
space-time. Approach to an event horizon corresponds to approach to a fixed
point; in general, the phase portrait of the equation illuminates the
qualitative features of the geometry. In particular, the asymptotics of the
red-shift as a horizon is approached, a critical ingredient of Hawking's
prediction of radiation from black holes, are easily brought out. This
asympotic behavior has elements in common with the universal behavior near
phase transitions in statistical physics. The validity of the Unruh vacuum for
the Hawking process can be understood in terms of this universality. The
concept of surface gravity is extended to to non-stationary spherically
symmetric black holes. Finally, it is shown that in the non-stationary case,
Hawking's predicted flux of radiation from a black hole would be modified.Comment: 20 pages, plain Tex, IOP macros, 4 eps figures, accepted by CQ
`Operational' Energy Conditions
I show that a quantized Klein-Gordon field in Minkowski space obeys an
`operational' weak energy condition: the energy of an isolated device
constructed to measure or trap the energy in a region, plus the energy it
measures or traps, cannot be negative. There are good reasons for thinking that
similar results hold locally for linear quantum fields in curved space-times. A
thought experiment to measure energy density is analyzed in some detail, and
the operational positivity is clearly manifested.
If operational energy conditions do hold for quantum fields, then the
negative energy densities predicted by theory have a will-o'-the-wisp
character: any local attempt to verify a total negative energy density will be
self-defeating on account of quantum measurement difficulties. Similarly,
attempts to drive exotic effects (wormholes, violations of the second law,
etc.) by such densities may be defeated by quantum measurement problems. As an
example, I show that certain attempts to violate the Cosmic Censorship
principle by negative energy densities are defeated.
These quantum measurement limitations are investigated in some detail, and
are shown to indicate that space-time cannot be adequately modeled classically
in negative energy density regimes.Comment: 18 pages, plain Tex, IOP macros. Expanded treatment of measurement
problems for space-time, with implications for Cosmic Censorship as an
example. Accepted by Classical and Quantum Gravit
HCN(1-0) enhancement in the bar of NGC 2903
We have mapped the \hcn emission from two spiral galaxies, NGC2903 and
NGC3504 to study the gas properties in the bars. The HCN(1-0) emission is
detected in the center and along the bar of NGC2903. The line ratio
HCN(1-0)/CO(1-0) ranges from 0.07 to 0.12 with the lowest value in the center.
The enhancement of HCN(1-0) emission along the bar indicates a higher fraction
of dense molecular gas in the bar than at the center. The mass of dense
molecular gas in the center (2.2x 10^7 Msun) is about 6 times lower than that
in the bar (1.2x 10^8 Msun). The total star formation rate (SFR) is estimated
to be 1.4 Msun/yr, where the SFR at the center is 1.9 times higher than that in
the bar. The time scale of consumption of the dense molecular gas in the center
is about 3x 10^7 yr which is much shorter than that in the bar of about 2 to 10
x 10^8 yr. The dynamical time scale of inflow of the gas from the bar to the
center is shorter than the consumption time scale in the bar, which suggests
that the star formation (SF) activity at the center is not deprived of fuel. In
the bar, the fraction of dense molecular gas mass relative to the total
molecular gas mass is twice as high along the leading edge than along the
central axis of the bar. The \hcn emission has a large velocity dispersion in
the bar, which can be attributed partially to the streaming motions indicative
of shocks along the bar. In NGC3504, the HCN(2-0) emission is detected only at
the center. The fraction of dense molecular gas mass in the center is about
15%. Comparison of the SFR with the predictions from numerical simulations
suggest that NGC2903 harbors a young type B bar with a strong inflow of gas
toward the center whereas NGC3504 has an older bar and has already passed the
phase of inflow of gas toward the center.Comment: Acceoted for publication in A&A, 12 figure
Molecular dark matter in galaxies
Clouds containing molecular dark matter in quantities relevant for star
formation may exist in minihaloes of the type of cold dark matter included in
many cosmological simulations or in the regions of some galaxies extending far
beyond their currently known boundaries. We have systematically explored
parameter space to identify conditions under which plane-parallel clouds
contain sufficient column densities of molecular dark matter that they could be
reservoirs for future star formation. Such clouds would be undetected or at
least appear by current observational criteria to be uninteresting from the
perspective of star formation. We use a time-dependent PDR code to produce
theoretical models of the chemistry and emission arising in clouds for our
chosen region of parameter space. We then select a subset of model clouds with
levels of emission that are low enough to be undetectable or at least
overlooked by current surveys. The existence of significant column densities of
cold molecular dark matter requires that the background radiation field be
several or more orders of magnitude weaker than that in the solar
neighbourhood. Lower turbulent velocities and cosmic ray induced ionization
rates than typically associated with molecular material within a kpc of the Sun
are also required for the molecular matter to be dark. We find that there is a
large region within the parameter space that results in clouds that might
contain a significant mass of molecular gas whilst remaining effectively
undetectable or at least not particularly noticeable in surveys. We note
briefly conditions under which molecular dark matter may contain a dynamically
interesting mass.Comment: 9 pages, 2 figures, accepted for publication in A&A; additional
concluding paragraph added at proof stag
Effective Area-Elasticity and Tension of Micro-manipulated Membranes
We evaluate the effective Hamiltonian governing, at the optically resolved
scale, the elastic properties of micro-manipulated membranes. We identify
floppy, entropic-tense and stretched-tense regimes, representing different
behaviors of the effective area-elasticity of the membrane. The corresponding
effective tension depends on the microscopic parameters (total area, bending
rigidity) and on the optically visible area, which is controlled by the imposed
external constraints. We successfully compare our predictions with recent data
on micropipette experiments.Comment: To be published in Phys. Rev. Let
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