2,382 research outputs found
The accretion of migrating giant planets
Most studies concerning the growth and evolution of massive planets focus
either on their accretion or their migration only. In this work we study both
processes concurrently to investigate how they might mutually affect each
other. We modeled a 2-dimensional disk with a steady accretion flow onto the
central star and embed a Jupiter mass planet at 5.2 au. The disk is locally
isothermal and viscosity is modeled using a constant . The planet is
held on a fixed orbit for a few hundred orbits to allow the disk to adapt and
carve a gap. After this period, the planet is released and free to move
according to the gravitational interaction with the gas disk. The mass
accretion onto the planet is modeled by removing a fraction of gas from the
inner Hill sphere, and the removed mass and momentum can be added to the
planet. Our results show that a fast migrating planet is able to accrete more
gas than a slower migrating planet. Utilizing a tracer fluid we analyzed the
origin of the accreted gas which comes predominantly originating from the inner
disk for a fast migrating planet. In case of slower migration the fraction of
gas from the outer disk increases. We also found that even for very high
accretion rates in some cases gas crosses the planetary gap from the inner to
the outer disk. Our simulations show that the crossing of gas changes during
the migration process as the migration rate slows down. Therefore classical
type II migration where the planet migrates with the viscous drift rate and no
gas crosses the gap is no general process but may only occur for special
parameters and at a certain time during the orbital evolution of the planet.Comment: 9 pages, 14 figures, accepted for publication in A&
On a CFT limit of planar -deformed SYM theory
We show that an integrable four-dimensional non-unitary field theory that was
recently proposed as a certain limit of the -deformed
SYM theory is incomplete and not conformal -- not even in the planar limit. We
complete this theory by double-trace couplings and find conformal one-loop
fix-points when admitting respective complex coupling constants. These
couplings must not be neglected in the planar limit, as they can contribute to
planar multi-point functions. Based on our results for certain two-loop planar
anomalous dimensions, we propose tests of integrability.Comment: LaTeX, 3 pages, 1 Figur
A piece of cake: the ground-state energies in gamma_i-deformed N=4 SYM theory
In the non-supersymmetric gamma_i-deformed N=4 SYM theory, the scaling
dimensions of the operators tr[Z^L] composed of L scalar fields Z receive
finite-size wrapping and prewrapping corrections in the 't Hooft limit. In this
paper, we calculate these scaling dimensions to leading wrapping order directly
from Feynman diagrams. For L>=3, the result is proportional to the maximally
transcendental `cake' integral. It matches with an earlier result obtained from
the integrability-based Luescher corrections, TBA and Y-system equations. At
L=2, where the integrability-based equations yield infinity, we find a finite
rational result. This result is renormalization-scheme dependent due to the
non-vanishing beta-function of an induced quartic scalar double-trace coupling,
on which we have reported earlier. This explicitly shows that conformal
invariance is broken - even in the 't Hooft limit.Comment: 21 pages, LaTeX, BibTeX, pstricks, feynm
The complete one-loop dilatation operator of planar real beta-deformed N=4 SYM theory
We determine the missing finite-size corrections to the asymptotic one-loop
dilatation operator of the real -deformed SYM theory for
the gauge groups and in the 't Hooft limit. In the case,
the absence of the field components leads to a new kind of finite-size
effect, which we call prewrapping. We classify which states are potentially
affected by prewrapping at generic loop orders and comment on the necessity to
include it into the integrability-based description. As a further result, we
identify classes of -point correlation functions which at all loop orders in
the planar theory are given by the values of their undeformed counterparts.
Finally, we determine the superconformal multiplet structure and one-loop
anomalous dimensions of all single-trace states with classical scaling
dimension .Comment: Latex, feynmp, pstricks, 37 pages, 6 tables, v2: formulations
improved, references added, typos corrected, v3: typos corrected, matches
published versio
On-Shell Methods for the Two-Loop Dilatation Operator and Finite Remainders
We compute the two-loop minimal form factors of all operators in the SU(2)
sector of planar N=4 SYM theory via on-shell unitarity methods. From the UV
divergence of this result, we obtain the two-loop dilatation operator in this
sector. Furthermore, we calculate the corresponding finite remainder functions.
Since the operators break the supersymmetry, the remainder functions do not
have the property of uniform transcendentality. However, the leading
transcendentality part turns out to be universal and is identical to the
corresponding BPS expressions. The remainder functions are shown to satisfy
linear relations which can be explained by Ward identities of form factors
following from R-symmetry.Comment: 24 pages; v2: typos corrected, some formulations clarified, matches
published versio
Integrating Abstract Caches with Symbolic Pipeline Analysis
Static worst-case execution time analysis of real-time tasks is based on abstract models that capture the timing behavior of the processor on which the tasks run. For complex processors, task-level execution time bounds are obtained by a state space exploration which involves the abstract model and the program. Partial state space exploration is not sound. Symbolic methods using binary decision diagrams (BDDs) allow for a full state space exploration of the pipeline, thereby maintaining soundness. Caches are too large to admit an efficient BDD representation. On the other hand, invariants of the cache state can be computed efficiently using abstract interpretation. How to integrate abstract caches with symbolic-state pipeline analysis is an open question. We propose a semi-symbolic domain to solve this problem. Statistical data from industrial-level software and WCET tools indicate that this new domain will enable an efficient analysis
Migration of massive planets in accreting disks
Massive planets that open a gap in the accretion disk are believed to migrate
with exactly the viscous speed of the disk, a regime termed type II migration.
Population synthesis models indicate that standard type II migration is too
rapid to be in agreement with the observations. We study the migration of
massive planets between and
corresponding to 0.2 to 2 Jupiter masses . in order to estimate the
migration rate in comparison to type II migration. We follow the evolution of
planets embedded in two-dimensional, locally isothermal disks with non-zero
mass accretion which is explicitly modelled using suitable in- and outflow
boundary conditions to ensure a specific accretion rate. After a certain
relaxation time we release the planet and measure its migration through the
disk and the dependence on parameters such as viscosity, accretion rate and
planet mass. We study accreting and non-accretion planets. The inferred
migration rate of the planet is determined entirely by the disk torques acting
on it and is completely independent of the viscous inflow velocity, so there is
no classical type II migration regime. Depending on the local disk mass the
migration rate can be faster or slower than type II migration. From the torques
and the accretion rate profile in the disk we see that the gap formed by the
planet does not separate the inner from the outer disk as necessary for type II
migration, rather gas crosses the gap or is accreted onto the planet.Comment: 10 pages, 16 figures, accepted for publication in A&
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