1,174 research outputs found
Consciousness makes a difference: A reluctant dualistâs confession
This paperâs outline is as follows. In sections 1-3 I give an exposi-tion of the Mind-Body Problem, with emphasis on what I believe to be the heart of the problem, namely, the Percepts-Qualia Nonidentity and its incompatibility with the Physical Closure Paradigm. In 4 I present the âQualia Inaction Postulateâ underlying all non-interactionist theo-ries that seek to resolve the above problem. Against this convenient postulate I propose in section 5 the âBafflement ArÂŹgument,â which is this paper's main thesis. Sections 6-11 critically disÂŹcuss attempts to dismiss the Bafflement Argument by the âBafÂŹflement=MisÂŹperception Equation.â Section 12 offers a refutation of all such attempts in the form of a concise âAsymmetry Proof.â Section 13 points out the bearing of the Bafflement Argument on the evolutionary role of consciousness while section 14 acknowledges the price that has to be paid for it in terms of basic physical principles. Section 15 summarizes the paper, pointing out the inescapability of interactionist dualism
Nonlocal Effects of Partial Measurements and Quantum Erasure
Partial measurement turns the initial superposition not into a definite
outcome but into a greater probability for it. The probability can approach
100%, yet the measurement can undergo complete quantum erasure. In the EPR
setting, we prove that i) every partial measurement nonlocally creates the same
partial change in the distant particle; and ii) every erasure inflicts the same
erasure on the distant particle's state. This enables an EPR experiment where
the nonlocal effect does not vanish after a single measurement but keeps
"traveling" back and forth between particles. We study an experiment in which
two distant particles are subjected to interferometry with a partial "which
path" measurement. Such a measurement causes a variable amount of correlation
between the particles. A new inequality is formulated for same-angle
polarizations, extending Bell's inequality for different angles. The resulting
nonlocality proof is highly visualizable, as it rests entirely on the
interference effect. Partial measurement also gives rise to a new form of
entanglement, where the particles manifest correlations of multiple
polarization directions. Another novelty in that the measurement to be erased
is fully observable, in contrast to prevailing erasure techniques where it can
never be observed. Some profound conceptual implications of our experiment are
briefly pointed out.Comment: To be published in Phys. Rev. A 63 (2001). 19 pages, 12 figures,
RevTeX 3.
Observational evidence for the shrinking of bright maser spots
The nature of maser emission means that the apparent angular size of an
individual maser spot is determined by the amplification process as well as by
the instrinsic size of the emitting cloud. Highly sensitive MERLIN radio
interferometry images spatially and spectrally resolve water maser clouds
around evolved stars. We measured the properties of clouds around the red
supergiant S Per and the AGB stars IK Tau, RT Vir, U Her and U Ori, to test
maser beaming theory. Spherical clouds are expected to produce an inverse
relationship between maser intensity and apparent size, which would not be seen
from cylindrical or slab-like regions. We analysed the maser properties, in
order to estimate the saturation state, and investigated the variation of
observed spot size with intensity and across the spectral line profiles.
Circumstellar masers emanate from discrete clouds from about one to 20 AU in
diameter depending on the star. Most of the maser features have negative
excitation temperatures close to zero and modest optical depths, showing that
they are mainly unsaturated. Around S Per and (at most epochs) RT Vir and IK
Tau, the maser component size shrinks with increasing intensity. In contrast,
the masers around U Ori and U Her tend to increase in size, with a larger
scatter. The water masers from S Per, RT Vir and IK Tau are mainly beamed into
spots with an observed angular size much smaller than the emitting clouds and
smallest of all at the line peaks. This suggests that the masers are
amplification-bounded, emanating from approximately spherical clouds. Many of
the masers around U Her and U Ori have apparent sizes which are more similar to
the emitting clouds and have less or no dependence on intensity, suggesting
that these masers are matter-bounded. This is consistent with an origin in
flattened clouds and these two stars have shown other behaviour indicating the
presence of shocks.Comment: 17 pages, 26 figure files, accepted by A&A 2010 Oct 2
Type I Superconductivity upon Monopole Condensation in Seiberg-Witten Theory
We study the confinement scenario in N=2 supersymmetric SU(2) gauge theory
near the monopole point upon breaking of N=2 supersymmetry by the adjoint
matter mass term. We confirm claims made previously that the
Abrikosov-Nielsen-Olesen string near the monopole point fails to be a BPS state
once next-to-leading corrections in the adjoint mass parameter taken into
account. Our results shows that type I superconductivity arises upon monopole
condensation. This conclusion allows us to make qualitative predictions on the
structure of the hadron mass spectrum near the monopole point.Comment: LaTex, 25 pages. Minor changes. To be published in NP
1â1=Counterfactual:on the potency and significance of quantum non-events
We study the unique role played in quantum mechanics by non-events or âcounterfactualsâ. Our earlier analysis of âquantum oblivionâ has revealed some subtle stages in the measurement process, which may end up in self-cancellation. To these findings, we now add two insights derived by two time-symmetric interpretations of quantum mechanics. (i) Like all quantum interactions, the non-event is formed by the conjunction of forward-plus-backward-evolving wave functions. (ii) Then, it is another feature of such dual evolutions, namely the involvement of negative masses and energies, that enables Nature to make some events âunhappenâ while leaving causal traces
The Nature of Deeply Buried Ultraluminous Infrared Galaxies: A Unified Model for Highly Obscured Dusty Galaxy Emission
We present models of deeply buried ultraluminous infrared galaxy (ULIRG)
spectral energy distributions (SEDs) and use them to construct a
three-dimensional diagram for diagnosing the nature of observed ULIRGs. Our
goal is to construct a suite of SEDs for a very simple model ULIRG structure,
and to explore how well this simple model can (by itself) explain the full
range of observed ULIRG properties. We use our diagnostic to analyze archival
Spitzer Space Telescope IRS spectra of ULIRGs and find that: (1) In general,
our model does provide a comprehensive explanation of the distribution of
mid-IR ULIRG properties; (2) >75% (in some cases 100%) of the bolometric
luminosities of the most deeply buried ULIRGs must be powered by a
dust-enshrouded active galactic nucleus; (3) an unobscured "keyhole" view
through <~10% of the obscuring medium surrounding a deeply buried ULIRG is
sufficient to make it appear nearly unobscured in the mid-IR; and (4) the
observed absence of deeply buried ULIRGs with large PAH equivalent widths is
naturally explained by our models showing that deep absorption features are
"filled-in" by small quantities of foreground unobscured PAH emission (e.g.,
from the host galaxy disk) at the level of ~1% the bolometric nuclear
luminosity. The modeling and analysis we present will also serve as a powerful
tool for interpreting the high angular resolution spectra of high-redshift
sources to be obtained with the James Webb Space Telescope.Comment: 20 pages, 14 figures. Accepted for publication in the Ap
Detections of water ice, hydrocarbons, and 3.3um PAH in z~2 ULIRGs
We present the first detections of the 3um water ice and 3.4um amorphous
hydrocarbon (HAC) absorption features in z~2 ULIRGs. These are based on deep
rest-frame 2-8um Spitzer IRS spectra of 11 sources selected for their
appreciable silicate absorption. The HAC-to-silicate ratio for our z~2 sources
is typically higher by a factor of 2-5 than that observed in the Milky Way.
This HAC `excess' suggests compact nuclei with steep temperature gradients as
opposed to predominantly host obscuration. Beside the above molecular
absorption features, we detect the 3.3um PAH emission feature in one of our
sources with three more individual spectra showing evidence for it. Stacking
analysis suggests that water ice, hydrocarbons, and PAH are likely present in
the bulk of this sample even when not individually detected. The most
unexpected result of our study is the lack of clear detections of the 4.67um CO
gas absorption feature. Only three of the sources show tentative signs of this
feature and at significantly lower levels than has been observed in local
ULIRGs. Overall, we find that the closest local analogs to our sources, in
terms of 3-4um color, HAC-to-silicate and ice-to-silicate ratios, as well as
low PAH equivalent widths are sources dominated by deeply obscured nuclei. Such
sources form only a small fraction of ULIRGs locally and are commonly believed
to be dominated by buried AGN. Our sample suggests that, in absolute number,
such buried AGN are at least an order of magnitude more common at z~2 than
today. The presence of PAH suggests that significant levels of star-formation
are present even if the obscured AGN typically dominate the power budget.Comment: 39 pages, 14 figures, accepted for publication in Ap
AGN Dusty Tori: II. Observational Implications of Clumpiness
From extensive radiative transfer calculations we find that clumpy torus
models with \No \about 5--15 dusty clouds along radial equatorial rays
successfully explain AGN infrared observations. The dust has standard Galactic
composition, with individual cloud optical depth \tV \about 30--100 at visual.
The models naturally explain the observed behavior of the 10\mic silicate
feature, in particular the lack of deep absorption features in AGN of any type.
The weak 10\mic emission feature tentatively detected in type 2 QSO can be
reproduced if in these sources \No drops to \about 2 or \tV exceeds \about 100.
The clouds angular distribution must have a soft-edge, e.g., Gaussian profile,
the radial distribution should decrease as or . Compact tori can
explain all observations, in agreement with the recent interferometric evidence
that the ratio of the torus outer to inner radius is perhaps as small as \about
5--10. Clumpy torus models can produce nearly isotropic IR emission together
with highly anisotropic obscuration, as required by observations. In contrast
with strict variants of unification schemes where the viewing-angle uniquely
determines the classification of an AGN into type 1 or 2, clumpiness implies
that it is only a probabilistic effect; a source can display type 1 properties
even from directions close to the equatorial plane. The fraction of obscured
sources depends not only on the torus angular thickness but also on the cloud
number \No. The observed decrease of this fraction at increasing luminosity can
be explained with a decrease of either torus angular thickness or cloud number,
but only the latter option explains also the possible emergence of a 10\mic
emission feature in QSO2.Comment: To appear in ApJ September 20, 200
MOLPOP-CEP: An Exact, Fast Code for Multi-Level Systems
We present MOLPOP-CEP, a universal line transfer code that allows the exact
calculation of multi-level line emission from a slab with variable physical
conditions for any arbitrary atom or molecule for which atomic data exist. The
code includes error control to achieve any desired level of accuracy, providing
full confidence in its results. Publicly available, MOLPOP-CEP employs our
recently developed Coupled Escape Probability (CEP) technique, whose
performance exceeds other exact methods by orders of magnitude. The program
also offers the option of an approximate solution with different variants of
the familiar escape probability method. As an illustration of the MOLPOP-CEP
capabilities we present an exact calculation of the Spectral Line Energy
Distribution (SLED) of the CO molecule and compare it with escape probability
results. We find that the popular large-velocity gradient (LVG) approximation
is unreliable at large CO column densities. Providing a solution of the
multi-level line transfer problem at any prescribed level of accuracy,
MOLPOP-CEP is removing any doubts about the validity of its final results.Comment: 10 pages, 3 figures, accepted for publication in A&
Weak Measurement of the Arrival Times of Single Photons and Pairs of Entangled Photons
In this paper we propose a setup for the weak measurement of photon arrival
time. It is found that the weak values of this arrival time can lie far away
from the expectation value, and in principle also in regions forbidden by
special relativity. We discuss in brief the implications of these results as
well as their reconciliation with the principle of causality. Furthermore, an
analysis of the weak arrival times of a pair of photons in a Bell state shows
that these weak arrival times are correlated.Comment: 4 pages, 1 figur
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