3,046 research outputs found
Goldstone boson counting in linear sigma models with chemical potential
We analyze the effects of finite chemical potential on spontaneous breaking
of internal symmetries within the class of relativistic field theories
described by the linear sigma model. Special attention is paid to the emergence
of ``abnormal'' Goldstone bosons with quadratic dispersion relation. We show
that their presence is tightly connected to nonzero density of the Noether
charges, and formulate a general counting rule. The general results are
demonstrated on an SU(3)xU(1) invariant model with an SU(3)-sextet scalar
field, which describes one of the color-superconducting phases of QCD.Comment: 10 pages, REVTeX4, 4 eps figures, v2: general discussion in Sec. IV
expanded and improved, references added, other minor corrections throughout
the tex
From Sociology and Economics to World History
World History has only recently emerged as a distinctive and vibrant field of study. Its origins arose from a cross-fertilization of economics, history, and comparative sociology, and from particular conjunctions of people and places in the 1980s and 1990s. World historians now, thanks to unprecedented access to quantitative historical data and international networks of scholars, can develop increasingly precise, formal, and detailed accounts of changes and comparisons across historical periods. However, our goal is not to create new master narratives or theories that predict a grand historical trajectory for mankind; rather we seek to better understand the similarities and differences among societies, and the likely consequences of those similarities and differences.World History has only recently emerged as a distinctive and vibrant field of study. Its origins arose from a cross-fertilization of economics, history, and comparative sociology, and from particular conjunctions of people and places in the 1980s and 1990s. World historians now, thanks to unprecedented access to quantitative historical data and international networks of scholars, can develop increasingly precise, formal, and detailed accounts of changes and comparisons across historical periods. However, our goal is not to create new master narratives or theories that predict a grand historical trajectory for mankind; rather we seek to better understand the similarities and differences among societies, and the likely consequences of those similarities and differences
The Once and Future Middle Kingdom: Chinaâs Return to Dominance in the Global Economy
Im 16. und 17. Jahrhundert fĂŒhrten alle Wege nach China. Die Nachfrage Europas nach chinesischer Seide, Keramik und Tee fĂŒhrte die europĂ€ischen Kaufleute in den Orient. Als Europa industrialisiert war, dominierten die EuropĂ€er den Welthandel, indem sie eine Reihe von StĂŒtzpunkten und Kolonien in Afrika, im Indischen Ozean und in China errichteten. Heute versucht China, diesen âdeviantenâ Trend umzukehren und China wieder zu seiner ânormalenâ Position als fĂŒhrende Wirtschaftsmacht zu verhelfen. China strebt nach einer FĂŒhrungsrolle in den Bereichen Wind- und Sonnenenergie, kĂŒnstlicher Intelligenz, ElektromobilitĂ€t und Quantencomputer, um die beherrschende Macht unter den Volkswirtschaften des 21. Jahrhunderts zu werden. AuĂerdem errichtet China eigene StĂŒtzpunkte quer durch den Indischen Ozean und nach SĂŒdeuropa, um seine Kontrolle ĂŒber diese Handelsrouten wiederherzustellen. Wenn China Erfolghat, wird es die letzten zweihundert Jahre der Weltwirtschaftsgeschichte umkehren und seine frĂŒhere Rolle als Hauptakteur in der globalen Wirtschaft wiederherstellen.In the sixteenth and seventeenth centuries, all roads led to China. Europeâs demand for Chinese silks, ceramics, and tea led European traders to the Orient. Then as Europe industrialized, Europeans came to dominate world trade, building a string of bases and colonies around Africa, across the Indian Ocean, and in China. Today, China is seeking to reverse this âdeviantâ trend and restore China to its ânormalâ position as the worldâs dominant economy. Seeking leadership in wind and solar power, artificial intelligence, electric vehicles, and quantum computing to become the dominant power among twenty-first century economies, China is also building its own set of bases across the Indian Ocean and into southern Europe to reassert its control of these trade routes. If China succeeds, it will reverse the last two hundred years of world economic history and reassert its earlier role as the core actor in the global economy
Uterine infusion of bacteria alters the transcriptome of bovine oocytes
Postpartum uterine infection reduces fertility in dairy cattle; however, the mechanisms of uterine infectionâmediated infertility are unknown. Paradoxically, infectionâinduced infertility persists after the resolution of disease. Oocytes are a finite resource, which are present at various stages of development during uterine infection. It is likely that oocyte development is influenced by uterine infectionâinduced changes to the follicular microenvironment. To better understand the impact of infection on oocyte quality we employed global transcriptomics of oocytes collected from heifers after receiving intrauterine infusion of pathogenic Escherichia coli and Trueperella pyogenes . We hypothesized that the oocyte transcriptome would be altered in response to intrauterine infection. A total of 452 differentially expressed genes were identified in oocytes collected from heifers 4 days after bacteria infusion compared to vehicle infusion, while 539 differentially expressed genes were identified in oocytes collected from heifers 60 days after bacteria infusion. Only 42 genes were differentially expressed in bacteriaâinfused heifers at both Day 4 and Day 60. Interferon, HMGB1, ILK, ILâ6, and TGFâbeta signaling pathways were downregulated in oocytes collected at Day 4 from bacteriaâinfused heifers, while interferon, ILK, and ILâ6 signaling were upregulated in oocytes collected at Day 60 from bacteriaâinfused heifers. These data suggest that bacterial infusion alters the oocyte transcriptome differently at Day 4 and Day 60, suggesting different follicle stages are susceptible to damage. Characterizing the longâterm impacts of uterine infection on the oocyte transcriptome aids in our understanding of how infection causes infertility in dairy cattle
Spontaneous symmetry breaking in the linear sigma model at finite chemical potential: One-loop corrections
We investigate spontaneous symmetry breaking within the linear sigma model
with the SU(2)xU(1) internal symmetry at finite chemical potential, which was
suggested as a model for kaon condensation in the CFL phase of dense quark
matter. One-loop corrections to the scalar field effective potential as well as
its propagator are calculated. Particular attention is paid to the type-II
Goldstone boson that appears in the Bose--Einstein condensed phase.
Furthermore, we show that the type-I Goldstone boson -- the superfluid phonon
-- is allowed to decay due to the nonlinearity of its dispersion relation at
high momentum, and determine its decay width.Comment: 13 pages, REVTeX4, 37 eps figures; v2: substantial error in Sec. IV
corrected, references added, other minor corrections; version to appear in
Phys. Rev.
``Induced'' Super-Symmetry Breaking with a Vanishing Vacuum Energy
A new mechanism for symmetry breaking is proposed which naturally avoids the
constraints following from the usual theorems of symmetry breaking. In the
context of super-symmetry, for example, the breaking may be consistent with a
vanishing vacuum energy. A 2+1 dimensional super-symmetric gauge field theory
is explicitly shown to break super-symmetry through this mechanism while
maintaining a zero vacuum energy. This mechanism may provide a solution to two
long standing problems, namely, dynamical super-symmetry breaking and the
cosmological constant problem.Comment: 12 pages, Late
A Quantum Adiabatic Evolution Algorithm Applied to Random Instances of an NP-Complete Problem
A quantum system will stay near its instantaneous ground state if the
Hamiltonian that governs its evolution varies slowly enough. This quantum
adiabatic behavior is the basis of a new class of algorithms for quantum
computing. We test one such algorithm by applying it to randomly generated,
hard, instances of an NP-complete problem. For the small examples that we can
simulate, the quantum adiabatic algorithm works well, and provides evidence
that quantum computers (if large ones can be built) may be able to outperform
ordinary computers on hard sets of instances of NP-complete problems.Comment: 15 pages, 6 figures, email correspondence to [email protected] ; a
shorter version of this article appeared in the April 20, 2001 issue of
Science; see http://www.sciencemag.org/cgi/content/full/292/5516/47
Revisiting Critical Vortices in Three-Dimensional SQED
We consider renormalization of the central charge and the mass of the supersymmetric Abelian vortices in 2+1 dimensions. We obtain
supersymmetric theory in 2+1 dimensions by dimensionally reducing the SQED in 3+1 dimensions with two chiral fields carrying opposite charges.
Then we introduce a mass for one of the matter multiplets without breaking N=2
supersymmetry. This massive multiplet is viewed as a regulator in the large
mass limit. We show that the mass and the central charge of the vortex get the
same nonvanishing quantum corrections, which preserves BPS saturation at the
quantum level. Comparison with the operator form of the central extension
exhibits fractionalization of a global U(1) charge; it becomes 1/2 for the
minimal vortex. The very fact of the mass and charge renormalization is due to
a "reflection" of an unbalanced number of the fermion and boson zero modes on
the vortex in the regulator sector.Comment: 24 pages, 2 figures Minor modifications, reference adde
Stability of the magnetic Schr\"odinger operator in a waveguide
The spectrum of the Schr\"odinger operator in a quantum waveguide is known to
be unstable in two and three dimensions. Any enlargement of the waveguide
produces eigenvalues beneath the continuous spectrum. Also if the waveguide is
bent eigenvalues will arise below the continuous spectrum. In this paper a
magnetic field is added into the system. The spectrum of the magnetic
Schr\"odinger operator is proved to be stable under small local deformations
and also under small bending of the waveguide. The proof includes a magnetic
Hardy-type inequality in the waveguide, which is interesting in its own
Engendering Accountability: Gender Crimes Under International Criminal Law
Gender crimes, such as rape, sexual assault, sexual slavery, and forced prostitution, have always been perpetrated during war, yet the laws of war have been slow to acknowledge these crimes and to bring their perpetrators to justice. This article examines the response of the International Criminal Tribunals for the Former Yugoslavia and Rwanda to this lacuna in international law, and analyzes the mainly positive developments they have made in this area in relation to the definition of rape and to the prosecution of gender crimes as crimes against humanity, war crimes, grave breaches of the Geneva Conventions, and genocide. It also traces the procedural safeguards instituted to facilitate the prosecution of gender crimes. The authors consider the way in which these advances have been taken forward in the Statute of the International Criminal Court, and the usefulness of other responses, such as the truth commissions in Bosnia and Yugoslavia, and the gacaca courts in Rwanda
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