360 research outputs found
Exact computation of one-loop correction to energy of spinning folded string in AdS_5 x S^5
We consider the 1-loop correction to the energy of folded spinning string
solution in the AdS_3 part of AdS_5 x S^5. The classical string solution is
expressed in terms of elliptic functions so an explicit computation of the
corresponding fluctuation determinants for generic values of the spin appears
to be a non-trivial problem. We show how it can be solved exactly by using the
static gauge expression for the string partition function (which we demonstrate
to be equivalent to the conformal gauge one) and observing that all the
corresponding second order fluctuation operators can be put into the standard
(single-gap) Lam\'e form. We systematically derive the small spin and large
spin expansions of the resulting expression for the string energy and comment
on some of their applications.Comment: 52 pp, 12 figures; v3: footnote 9 adde
Quantization of Sine-Gordon solitons on the circle: semiclassical vs. exact results
We consider the semiclassical quantization of sine-Gordon solitons on the
circle with periodic and anti-periodic boundary conditions. The 1-loop quantum
corrections to the mass of the solitons are determined using zeta function
regularization in the integral representation. We compare the semiclassical
results with exact numerical calculations in the literature and find excellent
agreement even outside the plain semiclassical regime.Comment: 20 pages, 5 figure
Semiclassical Strings in AdS_5 x S^5 and Automorphic Functions
Using AdS/CFT we derive from the folded spinning string ordinary differential
equations for the anomalous dimension of the dual N=4 SYM twist-two operators
at strong coupling. We show that for large spin the asymptotic solutions have
the Gribov-Lipatov recirocity property. To obtain this result we use a hidden
modular invariance of the energy-spin relation of the folded spinning string.
Further we identify the Moch-Vermaseren-Vogt (MVV) relations, which were first
recognized in plain QCD calculations, as the recurrence relations of the
asymptotic series ansatz.Comment: 4 page
On a generalization of Jacobi's elliptic functions and the Double Sine-Gordon kink chain
A generalization of Jacobi's elliptic functions is introduced as inversions
of hyperelliptic integrals. We discuss the special properties of these
functions, present addition theorems and give a list of indefinite integrals.
As a physical application we show that periodic kink solutions (kink chains) of
the double sine-Gordon model can be described in a canonical form in terms of
generalized Jacobi functions.Comment: 18 pages, 9 figures, 3 table
Statistical modelling of resolved debris discs
Es wurde eine Probe von 39 räumlich aufgelösten Trümmerschreiben mit der Absicht untersucht, Korrelationen zwischen den Zentralsternparametern und den Scheibenparametern zu finden. Eine Hürde war dabei die Entartung zwischen den Staubteilchengrößen und dem Ort des Staubs. Kleine Partikel in großer Entfernung lieferten gleiche Ergebnisse wie große Teilchen näher am Stern. Durch die Scheibenauflösung konnten die Radien mittels einer neuen Methode bestimmt und so die Entartung gebrochen werden. Die Modellierung der spektralen Energieverteilung war die Grundlage der Analyse, wobei 2 verschiedene Modelle genutzt wurden. Der Vergleich beider verdeutlichte, dass sie zu gleichen Korrelationen der Parameter führen, aber auch Unterschiede bei individuellen Scheiben sichtbar sind. Es wurde eine große Streuung der Scheibenradien über den gesamten Bereich der stellaren Leuchtkraft festgestellt. Daher scheint die entgültige Form der Scheibe nicht von temperaturabhängigen Prozessen abhängig zu sein. Der wahre Scheibenradius im Verhältnis zum Schwarzkörperradius zeigte einen Abfall mit zunehmender Leuchtkraft, was eine Schätzung des Radius von unaufgelösten Schreiben erlaubt. Die dominante Teilchengröße steigt leicht mit zunehmender Leuchtkraft an, jedoch ist der Anstieg auch mit einer konstanten Teilchengröße vereinbar. Erwartet wird aber ein steilerer Anstieg, bedingt durch wachsenden Strahlungsdruck. Daher ist ein Abfall der dominanten Teilchengröße in Ausstoßgrößen erkennbar, der hier auch die stärkste Korrelation darstellt. Es wurden mehrere Erklärungen für diesen Abfall untersucht, u.a. ein endliches Reservoir an Oberflächenenergie der kleinsten Staubteilchen und die Rolle der dynamischen Scheibenanregung. Erstere scheint nur von geringer Bedeutung zu sein. Letztere deutet darauf hin, dass die dynamische Anregung mit der Leuchtkraft zunimmt. Scheiben um leuchtkräftigere Sterne könnten daher massereichere Planeten/Planetesimale besitzen
Dust Spreading in Debris Discs: Do Small Grains Cling on to Their Birth Environment?
Debris discs are dusty belts of planetesimals around main-sequence stars,
similar to the asteroid and Kuiper belts in our solar system. The planetesimals
cannot be observed directly, yet they produce detectable dust in mutual
collisions. Observing the dust, we can try to infer properties of invisible
planetesimals. Here we address the question of what is the best way to measure
the location of outer planetesimal belts that encompass extrasolar planetary
systems. A standard method is using resolved images at mm-wavelengths, which
reveal dust grains with sizes comparable to the observational wavelength.
Smaller grains seen in the infrared (IR) are subject to several
non-gravitational forces that drag them away from their birth rings, and so may
not closely trace the parent bodies. In this study, we examine whether imaging
of debris discs at shorter wavelengths might enable determining the spatial
location of the exo-Kuiper belts with sufficient accuracy. We find that around
M-type stars the dust best visible in the mid-IR is efficiently displaced
inward from their birth location by stellar winds, causing the discs to look
more compact in mid-IR images than they actually are. However, around
earlier-type stars where the majority of debris discs is found, discs are still
the brightest at the birth ring location in the mid-IR regime. Thus, sensitive
IR facilities with good angular resolution, such as MIRI on JWST, will enable
tracing exo-Kuiper belts in nearby debris disc systems.Comment: 16 page
Quasi-doubly periodic solutions to a generalized Lame equation
We consider the algebraic form of a generalized Lame equation with five free
parameters. By introducing a generalization of Jacobi's elliptic functions we
transform this equation to a 1-dim time-independent Schroedinger equation with
(quasi-doubly) periodic potential. We show that only for a finite set of
integral values for the five parameters quasi-doubly periodic eigenfunctions
expressible in terms of generalized Jacobi functions exist. For this purpose we
also establish a relation to the generalized Ince equation.Comment: 15 pages,1 table, accepted for publication in Journal of Physics
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