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Pulsating Stellar Atmospheres  [PDF]
Dimitar D. Sasselov
Physics , 1997,
Abstract: We review the basic concepts, the present state of theoretical models, and the future prospects for theory and observations of pulsating stellar atmospheres. Our emphasis is on radially pulsating cool stars, which dynamic atmospheres provide a general example for the differences with standard static model atmospheres.
Mode selection in pulsating stars  [PDF]
R. Smolec
Physics , 2013, DOI: 10.1017/S1743921313014439
Abstract: In this review we focus on non-linear phenomena in pulsating stars the mode selection and amplitude limitation. Of many linearly excited modes only a fraction is detected in pulsating stars. Which of them and why (the problem of mode selection) and to what amplitude (the problem of amplitude limitation) are intrinsically non-linear and still unsolved problems. Tools for studying these problems are briefly discussed and our understanding of mode selection and amplitude limitation in selected groups of self-excited pulsators is presented. Focus is put on classical pulsators (Cepheids and RR Lyrae stars) and main sequence variables (delta Scuti and beta Cephei stars). Directions of future studies are briefly discussed.
Pulsating variable stars in the Magellanic Clouds  [PDF]
Gisella Clementini
Physics , 2009,
Abstract: Pulsating variable stars can be powerful tools to study the structure, formation and evolution of galaxies. I discuss the role that the Magellanic Clouds' pulsating variables play in our understanding of the whole Magellanic System, in light of results on pulsating variables produced by extensive observing campaigns like the MACHO and OGLE microlensing surveys. In this context, I also briefly outline the promise of new surveys and astrometric missions which will target the Clouds in the near future.
Asteroseismology of Pulsating Stars  [PDF]
Santosh Joshi,Yogesh C. Joshi
Physics , 2015, DOI: 10.1007/s12036-015-9327-z
Abstract: The success of helioseismology is due to its capability of measuring p-mode oscillations in the Sun. This allows us to extract informations on the internal structure and rotation of the Sun from the surface to the core. Similarly, asteroseismology is the study of the internal structure of the stars as derived from stellar oscillations. In this review we highlight the progress in the observational asteroseismology, including some basic theoretical aspects. In particular, we discuss our contributions to asteroseismology through the study of chemically peculiar stars under the "Nainital-Cape Survey" project being conducted at ARIES, Nainital since 1999. This survey aims to detect new rapidly-pulsating Ap (roAp) stars in the northern hemisphere. We also discuss the contribution of ARIES towards the asteroseismic study of the compact pulsating variables. We comment on the future prospects of our project in the light of the new optical 3.6-m telescope to be install at Devasthal (ARIES). Finally, we present a preliminary optical design of the high-speed imaging photometers for this telescope.
Stable Knotted Strings  [PDF]
Rui Dilao,Ricardo Schiappa
Physics , 1997, DOI: 10.1016/S0370-2693(97)00556-X
Abstract: We solve the Cauchy problem for the relativistic closed string in Minkowski space $M^{3+1}$, including the cases where the initial data has a knot like topology. We give the general conditions for the world sheet of a closed knotted string to be a time periodic surface. In the particular case of zero initial string velocity the period of the world sheet is proportional to half the length ($\ell$) of the initial string and a knotted string always collapses to a link for $t=\ell/4$. Relativistic closed strings are dynamically evolving or pulsating structures in spacetime, and knotted or unknotted like structures remain stable over time. The generation of arbitrary $n$-fold knots, starting with an initial simple link configuration with non zero velocity is possible.
The Onset of Chaos in Pulsating Variable Stars  [PDF]
David G. Turner,Leonid N. Berdnikov,J. R. Percy,Mohamed Abdel-Sabour Abdel-Latif
Physics , 2011,
Abstract: Random changes in pulsation period occur in cool pulsating Mira variables, Type A, B, and C semiregular variables, RV Tauri variables, and in most classical Cepheids. The physical processes responsible for such fluctuations are uncertain, but presumably originate in temporal modifications of the envelope convection in such stars. Such fluctuations are seemingly random over a few pulsation cycles of the stars, but are dominated by the regularity of the primary pulsation over the long term. The magnitude of stochasticity in pulsating stars appears to be linked directly to their dimensions, although not in simple fashion. It is relatively larger in M supergiants, for example, than in short-period Cepheids, but is common enough that it can be detected in visual observations for many types of pulsating stars. Although chaos was discovered in such stars 80 years ago, detection of its general presence in the group has only been possible in recent studies.
Amplitude Variations in Pulsating Yellow Supergiants  [PDF]
John R. Percy,Rufina Y. -H. Kim
Physics , 2014,
Abstract: It was recently discovered that the amplitudes of pulsating red giants and supergiants vary significantly on time scales of 20-30 pulsation periods. Here, we analyze the amplitude variability in 29 pulsating yellow supergiants (5 RVa, 4 RVb, 9 SRd, 7 long-period Cepheid, and 4 yellow hypergiant stars), using visual observations from the AAVSO International Database, and Fourier and wavelet analysis using the AAVSO's VSTAR package. We find that these stars vary in amplitude by factors of up to 10 or more (but more typically 3-5), on a mean time scale (L) of 33 +/- 4 pulsation periods (P). Each of the five sub-types shows this same behavior, which is very similar to that of the pulsating red giants, for which the median L/P was 31. For the RVb stars, the lengths of the cycles of amplitude variability are the same as the long secondary periods, to within the uncertainty of each.
Monodromic strings  [PDF]
C. Klimcik,S. Parkhomenko
Mathematics , 2000,
Abstract: We argue that apart from the standard closed and open strings one may consider a third possibility that we call monodromic strings. The monodromic string propagating on a target looks like an ordinary open string (a mapping from a segment to the target) but its space of states is isomorphic to that of a closed string. It is shown that the monodromic strings naturally appear in T-dualizing closed strings moving on simply connected targets. As a nontrivial topology changing example we show that the monodromic strings on a compact Poisson-Lie group are T-dual to the standard closed strings propagating on the noncompact dual PL group.
Pulsating enophthalmos in association with an orbital varix  [cached]
Prabhakaran Venkatesh,Selva Dinesh
Indian Journal of Ophthalmology , 2009,
Abstract: We report a case of pulsating enophthalmos secondary to orbital varix associated with orbital bony defects. A 64-year-old female with pulsating enophthalmos of the right eye was found to have a right orbital mass with bony defects of the orbit. Valsalva maneuver failed to induce proptosis. The diagnosis of orbital varix was confirmed by exploratory orbitotomy. During general anesthesia for orbitotomy, proptosis of the right eye was noted. Ophthalmologists should be aware of the association between orbital varices and cranial bony defects and encephaloceles. Proptosis induced by general anesthesia and positive pressure ventilation suggests an underlying distensible venous anomaly.
Properties of pulsating solitons in dissipative systems

Wu Liang,Guo Zhi-Jie,Song Li-Jun,

中国物理 B , 2010,
Abstract: In this paper, a set of detailed numerical simulations of pulsating solitons in certain regions, where the pulsating solitons exist, have been carried out. The results show that the transformation between pulsating soliton and fronts can be realised through a series of period-doubling bifurcations, while there exist many kinds of special solutions. The complete transformation diagram has been obtained when the value of nonlinear gain varies within a definite range. The detailed analysis of the diagram reveals that the pulsating soliton experiences period-doubling bifurcations for smaller values of the nonlinear gain. For larger values of it, the pulsating solitons show chaotic behaviour and complex pulse splitting except for some special bifurcations. With the value of nonlinear gain increasing further, the pulse profiles resume pulsating, but the pulse energy is much higher than before and the pulse centre may move along the propagation direction.
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