Hypervelocity particle capture: Some considerations regarding suitable target media

Hypervelocity particles colliding with passive capture media will be traversed by shock waves; depending on the stress amplitude, the particle may remain solid or it may melt or vaporize. Any capture mechanism considered for cosmic dust collection in low Earth-orbit must be designed such that sample alteration and hence loss of scientific information is minimized. Capture of pristine particles is fundamentally difficult, because the specific heat of melting and even vaporization is exceeded upon impact at typical, geocentric encounter velocities. From the results of calculated and observed melting behaviors it is concluded that shock stresses in excess of 50 GPA should be avoided during hypervelocity particle capture on board Space Station and that stresses 20 GPa, even at 15 km/s collision velocities, should constitute desirable instrument design goals. Some principal characteristics of the capture medium that may satisfy these requirements are identified

The ambivalent shadow of the pre-Wilsonian rise of international law

The generation of American international lawyers who founded the American Society of International Law in 1906 and nurtured the soil for what has been retrospectively called a “moralistic legalistic approach to international relations” remains little studied. A survey of the rise of international legal literature in the U.S. from the mid-19th century to the eve of the Great War serves as a backdrop to the examination of the boosting effect on international law of the Spanish American War in 1898. An examination of the Insular Cases before the US Supreme Court is then accompanied by the analysis of a number of influential factors behind the pre-war rise of international law in the U.S. The work concludes with an examination of the rise of natural law doctrines in international law during the interwar period and the critiques addressed.by the realist founders of the field of “international relations” to the “moralistic legalistic approach to international relation

Impact cratering in reduced-gravity environments: Early experiments on the NASA KC-135 aircraft

Impact experimentation on the NASA KC-135 Reduced-Gravity Aircraft was shown to be possible, practical, and of considerable potential use in examining the role of gravity on various impact phenomena. With a minimal facility, crater dimensional and growth-times were measured, and have demonstrated both agreement and disagreement with predictions. A larger facility with vacuum capability and a high-velocity gun would permit a much wider range of experimentation

Rolling of asymmetric disks on an inclined plane

In a recent papers, Turner and Turner (2010 {\em Am. J. Phys.} {\bf 78} 905-7) and Jensen (2011 {\em Eur. J. Phys.} {\bf 32} 389-397) analysed the motion of asymmetric rolling rigid bodies on a horizontal plane. These papers addressed the common misconception that the instantaneous point of contact of the rolling body with the plane can be used to evaluate the angular momentum $\mathbf L$ and the torque $\boldsymbol\tau$ in the equation of motion $d\mathbf L/dt = \boldsymbol\tau$. To obtain the correct equation of motion, the "phantom torque" or various rules that depend on the motion of the point about which $\mathbf L$ and $\boldsymbol\tau$ are evaluated were discussed. In this paper, I consider asymmetric disks rolling down an inclined plane and describe the most basic way of obtaining the correct equation of motion; that is, to choose the point about which $\mathbf L$ and $\boldsymbol\tau$ are evaluated that is stationary in an inertial frame

The Chagos Islands cases: the empire strikes back

Good governance requires the accommodation of multiple interests in the cause of decision making. However, undue regard for particular sectional interests can take their toll upon public faith in government administration. Historically, broad conceptions of the good of the commonwealth were employed to outweigh the interests of groups that resisted colonisation. In the decision making of the British Empire, the standard approach for justifying the marginalisation of the interests of colonised groups was that they were uncivilised and that particular hardships were the price to be paid for bringing to them the imperial dividend of industrial society. It is widely assumed that with the dismantling of the British Empire, such impulses and their accompanying jurisprudence became a thing of the past. Even as decolonisation proceeded apace after the Second World War, however, the United Kingdom maintained control of strategically important islands with a view towards sustaining its global role. In an infamous example from this twilight period of empire, in the 1960s imperial interests were used to justify the expulsion of the Chagos islanders from the British Indian Ocean Territory (BIOT). Into the twenty-first century, this forced elision of the UK’s interests with the imperial “common good” continues to take centre stage in courtroom battles over the islanders’ rights, being cited before domestic and international tribunals in order to maintain the Chagossians’ exclusion from their homeland. This article considers the new jurisprudence of imperialism which has emerged in a string of decisions which have continued to marginalise the Chagossians’ interests

Higgs mediated Double Flavor Violating top decays in Effective Theories

The possibility of detecting double flavor violating top quark transitions at future colliders is explored in a model-independent manner using the effective Lagrangian approach through the $t \to u_i\tau \mu$ ($u_i=u,c$) decays. A Yukawa sector that contemplates $SU_L(2)\times U_Y(1)$ invariants of up to dimension six is proposed and used to derive the most general flavor violating and CP violating $q_iq_jH$ and $l_il_jH$ vertices of renormalizable type. Low-energy data, on high precision measurements, and experimental limits are used to constraint the $tu_iH$ and $H\tau \mu$ vertices and then used to predict the branching ratios for the $t \to u_i\tau \mu$ decays. It is found that this branching ratios may be of the order of $10^{-4}-10^{-5}$, for a relative light Higgs boson with mass lower than $2m_W$, which could be more important than those typical values found in theories beyond the standard model for the rare top quark decays $t\to u_iV_iV_j$ ($V_i=W,Z,\gamma, g$) or $t\to u_il^+l^-$. %% LHC experiments, by using a total integrated luminosity of $\rm 3000 fb^{-1}$ of data, will be able to rule out, at 95% C.L., DFV top quark decays up to a Higgs mass of 155 GeV/$c^2$ or discover such a process up to a Higgs mass of 147 GeV/$c^2$.Comment: 24 pages, 11 figure

Structure of the neutron-rich N=7 isotones 10Li and 9He

The near threshold structure of the unbound N=7 isotones 10Li and 9He has been investigated using proton removal and breakup from intermediate energy (35 MeV/nucleon) secondary beams of 11Be and 14,15B. The coincident detection of the beam velocity 9Li and 8He fragments and neutrons permitted the relative energy of the in-flight decay of 10Li and 9He to be reconstructed. Both systems were found to exhibited virtual s-wave strength near threshold together with a higher-lying resonance.Comment: 4 pages, 2 figures, Contribution to INPC2010 - "International Nuclear Physics Conference", Vancouver, Canada, 4-9 July 2010, Proceedings to be published in Journal of Physics: Conference Serie

One-loop Beta Functions for the Orientable Non-commutative Gross-Neveu Model

We compute at the one-loop order the beta-functions for a renormalisable non-commutative analog of the Gross Neveu model defined on the Moyal plane. The calculation is performed within the so called x-space formalism. We find that this non-commutative field theory exhibits asymptotic freedom for any number of colors. The beta-function for the non-commutative counterpart of the Thirring model is found to be non vanishing.Comment: 16 pages, 9 figure

Neutrino masses in the Lepton Number Violating MSSM

We consider the most general supersymmetric model with minimal particle content and an additional discrete Z_3 symmetry (instead of R-parity), which allows lepton number violating terms and results in non-zero Majorana neutrino masses. We investigate whether the currently measured values for lepton masses and mixing can be reproduced. We set up a framework in which Lagrangian parameters can be initialised without recourse to assumptions concerning trilinear or bilinear superpotential terms, CP-conservation or intergenerational mixing and analyse in detail the one loop corrections to the neutrino masses. We present scenarios in which the experimental data are reproduced and show the effect varying lepton number violating couplings has on the predicted atmospheric and solar mass^2 differences. We find that with bilinear lepton number violating couplings in the superpotential of the order 1 MeV the atmospheric mass scale can be reproduced. Certain trilinear superpotential couplings, usually, of the order of the electron Yukawa coupling can give rise to either atmospheric or solar mass scales and bilinear supersymmetry breaking terms of the order 0.1 GeV^2 can set the solar mass scale. Further details of our calculation, Lagrangian, Feynman rules and relevant generic loop diagrams, are presented in three Appendices.Comment: 48 pages, 7 figures, v2 references added, typos corrected, published versio

The stability of the O(N) invariant fixed point in three dimensions

We study the stability of the O(N) fixed point in three dimensions under perturbations of the cubic type. We address this problem in the three cases $N=2,3,4$ by using finite size scaling techniques and high precision Monte Carlo simulations. It is well know that there is a critical value $2<N_c<4$ below which the O(N) fixed point is stable and above which the cubic fixed point becomes the stable one. While we cannot exclude that $N_c<3$, as recently claimed by Kleinert and collaborators, our analysis strongly suggests that $N_c$ coincides with 3.Comment: latex file of 18 pages plus three ps figure