Self-force and synchrotron radiation in odd space-time dimensions

Classical electrodynamics in flat 3+1 space-time has a very special retarded propagator delta(x^2) localized on the light cone, so that a particle does not interact with its past field. However, this is an exception, and in flat odd-dimensional space-times as well as generic curved spaces this is not so. In this work we show that the so called self-force is not only non-zero, but it matches (in 2+1 dimensions) the radiation reaction force derived from the radiation intensity.Comment: 9 pages, 1 figur

Formal Properties as the Basis for Value in Music

This paper defends the thesis that value in a piece of music is based in its formal properties rather than its non-formal properties. Two arguments are presented to support this conclusion. The first argument shows that if value in music is to be objective, then it must be grounded in a piece\u27s formal properties rather than its non-formal properties. In the second argument, a number of alternate possibilities for grounding value in music are considered and shown to miss the mark or be inadequate. Finally, a number of possible objections against the arguments and conclusion are considered and possible responses to them given

Supererogation and Moral Reasons

This paper is about the paradox of supererogation and why supererogation is morally optional. I argue that supererogation is morally optional because it is supported by both moral reasons and nonmoral reasons. I understand moral reasons to be agent-neutral reasons that apply to everybody while nonmoral reasons are agent-relative reasons that don’t apply to everybody. By understanding supererogation in this way, I have rejected the common assumption that what makes supererogation supererogatory is moral. Instead I argue that the source of supererogation is nonmoral. One important upshot to this is that unlike those who claim that the source of supererogation is moral, I do not have to deny the moral overridingness of moral reasons

Baryons still trace dark matter: probing CMB lensing maps for hidden isocurvature

Compensated isocurvature perturbations (CIPs) are primordial fluctuations that balance baryon and dark-matter isocurvature to leave the total matter density unperturbed. The effects of CIPs on the cosmic microwave background (CMB) anisotropies are similar to those produced by weak lensing of the CMB: smoothing of the power spectrum, and generation of non-Gaussian features. Previous work considered the CIP effects on the CMB power-spectrum but neglected to include the CIP effects on estimates of the lensing potential power spectrum (though its contribution to the non-Gaussian, connected, part of the CMB trispectrum). Here, the CIP contribution to the standard estimator for the lensing potential power-spectrum is derived, and along with the CIP contributions to the CMB power-spectrum, Planck data is used to place limits on the root-mean-square CIP fluctuations on CMB scales, $\Delta_{\rm rms}^2(R_{\rm CMB})$. The resulting constraint of $\Delta_{\rm rms}^2(R_{\rm CMB}) < 4.3 \times 10^{-3}$ using this new technique improves on past work by a factor of $\sim 3$. We find that for Planck data our constraints almost reach the sensitivity of the optimal CIP estimator. The method presented here is currently the most sensitive probe of the amplitude of a scale-invariant CIP power spectrum placing an upper limit of $A_{\rm CIP}< 0.017$ at 95% CL. Future measurements of the large-scale CMB lensing potential power spectrum could probe CIP amplitudes as low as $\Delta_{\rm rms}^2(R_{\rm CMB}) = 8 \times 10^{-5}$ ($A_{\rm CIP} = 3.2 \times 10^{-4}$).Comment: 24 pages, 9 figures; comments welcome; v2 references correcte

Another integrable case in the Lorenz model

A scaling invariance in the Lorenz model allows one to consider the usually discarded case sigma=0. We integrate it with the third Painlev\'e function.Comment: 3 pages, no figure, to appear in J. Phys.

Baryons Still Trace Dark Matter: Probing CMB Lensing Maps For Hidden Isocurvature

Compensated isocurvature perturbations (CIPs) are primordial fluctuations that balance baryon and dark-matter isocurvature to leave the total matter density unperturbed. The effects of CIPs on the cosmic microwave background (CMB) anisotropies are similar to those produced by weak lensing of the CMB: smoothing of the power spectrum and generation of non-Gaussian features. Here, an entirely new CIP contribution to the standard estimator for the lensing-potential power spectrum is derived. Planck measurements of the temperature and polarization power spectrum, as well as estimates of CMB lensing, are used to place limits on the variance of the CIP fluctuations on CMB scales, Δ2rms(RCMB). The resulting constraint of Δ2rms(RCMB)\u3c4.3×10−3 at 95% confidence level (CL) using this new technique improves on past work by a factor of ∼3. We find that for Planck data our constraints almost reach the sensitivity of the optimal CIP estimator. The method presented here is currently the most sensitive probe of the amplitude of a scale-invariant CIP power spectrum, ACIP, placing an upper limit of ACIP\u3c0.017 at 95% CL. Future measurements of the large-scale CMB lensing-potential power spectrum could probe CIP amplitudes as low as Δ2rms(RCMB)=8×10−5 at 95% CL (corresponding to ACIP=3.2×10−4)