70 research outputs found
Charge transport and phase transition in exciton rings
The macroscopic exciton rings observed in the photoluminescence (PL) patterns
of excitons in coupled quantum wells (CQWs) are explained by a series of
experiments and a theory based on the idea of carrier imbalance, transport and
recombination. The rings are found to be a source of cold excitons with
temperature close to that of the lattice. We explored states of excitons in the
ring over a range of temperatures down to 380 mK. These studies reveal a sharp,
albeit continuous, second order phase transition to a low-temperature ordered
exciton state, characterized by ring fragmentation into a periodic array of
aggregates. An instability at the onset of degeneracy in the cold exciton
system, due to stimulated exciton formation, is proposed as the transition
mechanism.Comment: 8 pages including 4 figure
Stopping of relativistic projectiles in two-component plasmas
Relativistic and correlation contributions to the polarizational energy losses of heavy
projectiles moving in dense two-component plasmas are analyzed within the method of moments
that allows one to reconstruct the Lindhard loss function from its three independently known power
frequency moments. The techniques employed result in a thorough separation of the relativistic
and correlation corrections to the classical asymptotic form for the polarizational losses obtained
by Bethe and Larkin. The above corrections are studied numerically at different values of plasma
parameters to show that the relativistic contribution enhances only slightly the corresponding
value of the stopping power.This research was financially supported by the Spanish Ministerio de Educacion y Ciencia Project No. ENE2010-21116-C02-02 and by the Science Committee of the Ministry of Education and Sciences of the Republic of Kazakhstan under Grants No. 1128/GF, 1129/GF and 1099/GF. IMT acknowledges the hospitality of the al-Farabi Kazakh National University.Arkhipov, YV.; Ashikbayeva, AB.; Askaruly, A.; Davletov, AE.; Tkachenko Gorski, IM. (2013). Stopping of relativistic projectiles in two-component plasmas. EPL. 104(3):35003-p1-35003-p6. https://doi.org/10.1209/0295-5075/104/35003S35003-p135003-p6104
Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy
We review HB stars in a broad astrophysical context, including both variable
and non-variable stars. A reassessment of the Oosterhoff dichotomy is
presented, which provides unprecedented detail regarding its origin and
systematics. We show that the Oosterhoff dichotomy and the distribution of
globular clusters (GCs) in the HB morphology-metallicity plane both exclude,
with high statistical significance, the possibility that the Galactic halo may
have formed from the accretion of dwarf galaxies resembling present-day Milky
Way satellites such as Fornax, Sagittarius, and the LMC. A rediscussion of the
second-parameter problem is presented. A technique is proposed to estimate the
HB types of extragalactic GCs on the basis of integrated far-UV photometry. The
relationship between the absolute V magnitude of the HB at the RR Lyrae level
and metallicity, as obtained on the basis of trigonometric parallax
measurements for the star RR Lyrae, is also revisited, giving a distance
modulus to the LMC of (m-M)_0 = 18.44+/-0.11. RR Lyrae period change rates are
studied. Finally, the conductive opacities used in evolutionary calculations of
low-mass stars are investigated. [ABRIDGED]Comment: 56 pages, 22 figures. Invited review, to appear in Astrophysics and
Space Scienc
Galvanomagnetic and Thermomagnetic Properties of a Nonideal Xenon Plasma at Megabar Pressures in Megagauss Magnetic Fields
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