Gravitációs terek aszimptotikus viselkedésének elméleti vizsgálata = Theoretical investigations of asymptotic properties of gravitational fields

Olyan általános numerikus eljárást fejlesztettünk ki, amelynek segítségével különféle gömbszimmetrikus, nemlineáris hiperbolikus fejlődési egyenletnek eleget tevő rendszerek evolúcióját tudjuk tanulmányozni. A sugárzási jelenségek hű leírását a konformis kompaktifikáció alkalmazásával biztosítottuk. Mind numerikus, mind pedig analitikus módszerekkel leírtuk az SU(2)Yang-Mills-Higgs rendszerek gerjesztett mágneses monopólusainak időfejlődését. Analitikus eszközök felhasználásával megmutattuk, hogy a tömeges mezőkidőfejlődése során szükségképpen nagyfrekvenciás rezgésekből felépülő, önhasonló módon táguló energia-héjak rendszere alakul ki. Megmutattuk, hogy a phi^4-es önkölcsönható potenciállal rendelkező skalárelméletek oszcillon típusú állapotai nem lehetnek tisztán periodikusak. A gravitációhoz minimálisan csatolt skalártér esetén az Einstein-anyagrendszert leíró téregyenletek egy kevert elliptikus-hiperbolikus rendszert alkotnak. Megmutattuk, hogy ezekből az egyenletekből az evolúciós vektormező megfelelő megválasztása révén egy elsőrendű szimmetrikus, tisztán hiperbolikus rendszert nyerhetünk. Lényegében tetszőleges kezdőérték problémák és tetszőleges gravitáció-anyag csatolt rendszerei esetében meghatároztuk azokat a feltételeket, amelyek téridőszimmetriák létezését biztosíthatják az időfejlődési tartományban. | We have developed a generic numerical method that is suitable to study the evolution of spherically symmetric non-linear systems satisfying hyperbolic equations. In order to have a method proper to study the true radiation processes the conformal rescaling have been applied. We have described the evolution of excited magnetic monopoles in thetheory of SU(2) Yang-Mills-Higgs systems by both numerical andanalytic methods. By making use of an analytic approach we have demonstrated that the evolution of massive fields can be characterised by the appearance of self-similarly expanding energy-shells built up from high frequency oscillations. We have shown that the oscillon states appearing already in thesimplest scalar theory with a phi^4 type self-interaction term cannot be purely period states. In minimally coupled Einstein matter theories the field equations in general are known to form a mixed elliptic-hyperbolic system. We have demonstrated that by a suitable choice for the time evolution vectorfield these equations turn into a simple first order symmetric hyperbolic system. We have determined the conditions that guarantee the existence of spacetime symmetries in the entire Cauchy development for essentially arbitrary initial value problem associated with arbitrary gravity matter systems

The Inadvisability of Nonuniformity in the Licensing of Cover Songs

In February 2015, the U.S. Copyright Office released a report entitled Copyright and the Music Marketplace, which summarizes its study of the music industry and recommends significant revisions to copyright law in response to the rapidly changing demands of the industry. Among its recommendations, the Copyright Office proposes an amendment to section 115(a)(2) of the Copyright Act. Currently, section 115(a)(2), referred to as the compulsory licensing provision of copyright law, permits someone to record a new version of a previously recorded and publicly distributed song, regardless of the format of the newly recorded version. The revised section 115(a)(2) would require someone who wishes to distribute a cover recording of a song to seek a license from the copyright owner for dissemination via interactive new media and digital downloads. However, distribution of cover songs in physical formats still would be subject to compulsory licensing. The Copyright Office’s suggested amendment to section 115(a)(2) would create nonuniformity for creators of cover recordings based on the intended format of the newly recorded song. This approach seems contrary to the Copyright Office’s guiding principles and reasoning behind its recommendations for other changes to copyright law in the Music Marketplace report that emphasize the importance of harmonization of the rules for music licensing. For example, the Copyright Office supports harmonizing the rules that govern terrestrial radio with the rules concerning digital and satellite radio by broadening the sound recording performance right to include terrestrial broadcasts and including terrestrial uses under sections 112 and 114 licenses. According to the report, the creation of a terrestrial radio performance right would adhere to the Office’s principle that “analogous uses should be treated alike.” Yet, the recommendation for section 115(a)(2) would produce different treatments of digital and physical formats of works. A potential licensee who is the digital distributor of a cover song would no longer have the option of a compulsory license if the licensee does not want to contact the copyright owner or the copyright owner does not wish to license the song, but the potential licensee could distribute the same cover song in a physical format, such as a compact disc (CD), under the current compulsory licensing system. This Article concludes this recommendation is inadvisable because it creates inconsistencies in licensing musical works when harmonization is critical for the music industry, and it places an unjustifiable burden on musicians and distributors seeking to rerecord songs in digital formats. The U.S. Copyright Office should either recommend the elimination of the compulsory licensing system for music or suggest format-neutral changes to the current system. Because of the lack of need and purpose for a compulsory licensing system for musical works today, the Article suggests that the Office develop a recommendation that includes the repeal of section 115

On the Cover

Frontismatter of the issue and explanation of the cover illustration, courtesy of the Linda Hall Library of Science, Engineering & Technology