1,370 research outputs found
Monumental Questions and How We Honor Them
We are in another moment where who and how we memorialize is being reconsidered in communities small and large. My colleague, Zachary Bray, and I proposed this symposium to the Kentucky Law Journal because the topic reflected our shared interests in the debate over memorials and which historical narrative should triumph in the public square. We arrive at the question from different intellectual paths, but the common concern is over when and how stakeholders can and will revise that narrative through the regulation of monuments. These revisions often come in the form of calls for, it not outright, removal outhouse materials that do not fit with the communities current or aspirant view of itself and its history
No-Hair Theorem for Spontaneously Broken Abelian Models in Static Black Holes
The vanishing of the electromagnetic field, for purely electric
configurations of spontaneously broken Abelian models, is established in the
domain of outer communications of a static asymptotically flat black hole. The
proof is gauge invariant, and is accomplished without any dependence on the
model. In the particular case of the Abelian Higgs model, it is shown that the
only solutions admitted for the scalar field become the vacuum expectation
values of the self-interaction.Comment: 8 pages, 2 figures, RevTeX; some changes to match published versio
Plasmon attenuation and optical conductivity of a two-dimensional electron gas
In a ballistic two-dimensional electron gas, the Landau damping does not lead
to plasmon attenuation in a broad interval of wave vectors q << k_F. Similarly,
it does not contribute to the optical conductivity \sigma (\omega, q) in a wide
domain of its arguments, E_F > \omega > qv_F, where E_F, k_F and v_F are,
respectively, the Fermi energy, wavevector and velocity of the electrons. We
identify processes that result in the plasmon attenuation in the absence of
Landau damping. These processes are: the excitation of two electron-hole pairs,
phonon-assisted excitation of one pair, and a direct plasmon-phonon conversion.
We evaluate the corresponding contributions to the plasmon linewidth and to the
optical conductivity.Comment: 8 pages, 4 figures; final form, misprints correcte
Lowland river responses to intraplate tectonism and climate forcing quantified with luminescence and cosmogenic 10Be
Intraplate tectonism has produced large-scale folding that steers regional drainage systems, such as the 1600 km-long Cooper Ck, en route to Australia’s continental depocentre at Lake Eyre. We apply cosmogenic 10Be exposure dating in bedrock, and luminescence dating in sediment, to quantify the erosional and depositional response of Cooper Ck where it incises the rising Innamincka Dome. The detachment of bedrock joint-blocks during extreme floods governs the minimum rate of incision (17.4±6.5 mm/ky) estimated using a numerical model of episodic erosion calibrated with our 10Be measurements. The last big-flood phase occurred no earlier than ~112–121ka. Upstream of the Innamincka Dome long-term rates of alluvial deposition, partly reflecting synclinal-basin subsidence, are estimated from 47 luminescence dates in sediments accumulated since ~270 ka. Sequestration of sediment in subsiding basins such as these may account for the lack of Quaternary accumulation in Lake Eyre, and moreover suggests that notions of a single primary depocentre at base-level may poorly represent lowland, arid-zone rivers. Over the period ~75–55 ka Cooper Ck changed from a bedload- dominant, laterally-active meandering river to a muddy anabranching channel network up to 60 km wide. We propose that this shift in river pattern was a product of base-level rise linked with the slowly deforming syncline–anticline structure, coupled with a climate-forced reduction in discharge. The uniform valley slope along this subsiding alluvial and rising bedrock system represents an adjustment between the relative rates of deformation and the ability of greatly enhanced flows at times during the Quaternary to incise the rising anticline. Hence, tectonic and climate controls are balanced in the long term
On 't Hooft's S-matrix Ansatz for quantum black holes
The S-matrix Ansatz has been proposed by 't Hooft to overcome difficulties
and apparent contradictions of standard quantum field theory close to the black
hole horizon. In this paper we revisit and explore some of its aspects. We
start by computing gravitational backreaction effects on the properties of the
Hawking radiation and explain why a more powerful formalism is needed to encode
them. We then use the map bulk-boundary fields to investigate the nature of
exchange algebras satisfied by operators associated with ingoing and outgoing
matter. We propose and comment on some analogies between the non covariant form
of the S-matrix amplitude and liquid droplet physics to end up with
similarities with string theory amplitudes via an electrostatic analogy. We
finally recall the difficulties that one encounters when trying to incorporate
non linear gravity effects in 't Hooft's S-matrix and observe how the inclusion
of higher order derivatives might help in the black hole microstate counting.Comment: 22 Pages. Latex Fil
Ten Proofs of the Generalized Second Law
Ten attempts to prove the Generalized Second Law of Thermodyanmics (GSL) are
described and critiqued. Each proof provides valuable insights which should be
useful for constructing future, more complete proofs. Rather than merely
summarizing previous research, this review offers new perspectives, and
strategies for overcoming limitations of the existing proofs. A long
introductory section addresses some choices that must be made in any
formulation the GSL: Should one use the Gibbs or the Boltzmann entropy? Should
one use the global or the apparent horizon? Is it necessary to assume any
entropy bounds? If the area has quantum fluctuations, should the GSL apply to
the average area? The definition and implications of the classical,
hydrodynamic, semiclassical and full quantum gravity regimes are also
discussed. A lack of agreement regarding how to define the "quasi-stationary"
regime is addressed by distinguishing it from the "quasi-steady" regime.Comment: 60 pages, 2 figures, 1 table. v2: corrected typos and added a
footnote to match the published versio
Does a Computer have an Arrow of Time?
In [Sch05a], it is argued that Boltzmann's intuition, that the psychological
arrow of time is necessarily aligned with the thermodynamic arrow, is correct.
Schulman gives an explicit physical mechanism for this connection, based on the
brain being representable as a computer, together with certain thermodynamic
properties of computational processes. [Haw94] presents similar, if briefer,
arguments. The purpose of this paper is to critically examine the support for
the link between thermodynamics and an arrow of time for computers. The
principal arguments put forward by Schulman and Hawking will be shown to fail.
It will be shown that any computational process that can take place in an
entropy increasing universe, can equally take place in an entropy decreasing
universe. This conclusion does not automatically imply a psychological arrow
can run counter to the thermodynamic arrow. Some alternative possible explana-
tions for the alignment of the two arrows will be briefly discussed.Comment: 31 pages, no figures, publication versio
General Relativistic Mean Field Theory for Rotating Nuclei
We formulate a general relativistic mean field theory for rotating nuclei
starting from the special relativistic model Lagrangian. The
tetrad formalism is adopted to generalize the model to the accelerated frame.Comment: 13 pages, REVTeX, no figures, submitted to Phys. Rev. Lett., the word
`curved' is replaced by `non-inertial' or `accelerated' in several places to
clarify the physical situation interested, some references are added, more
detail discussions are given with omitting some redundant sentence
Cold Plasma Wave Analysis in Magneto-Rotational Fluids
This paper is devoted to investigate the cold plasma wave properties. The
analysis has been restricted to the neighborhood of the pair production region
of the Kerr magnetosphere. The Fourier analyzed general relativistic
magnetohydrodynamical equations are dealt under special circumstances and
dispersion relations are obtained. We find the -component of the complex
wave vector numerically. The corresponding components of the propagation
vector, attenuation vector, phase and group velocities are shown in graphs. The
direction and dispersion of waves are investigated.Comment: 22 pages, 18 figures, accepted for publication in Astrophys. Space
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