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8821867646576398bdb290a27a4b6e4f8ff71f80
subsection
271
289
Euclidean Conjugation
The "Euclidean Conjugation" acts on \mathbb {C}{P}^1 in an obvious way, \text{⌃}: \left[\pi ^{A^{\prime }}\right] \mapsto \left[\hat{\pi }^{A^{\prime }}\right] . This is now an involution but importantly it has no fix points. Its representation in inhomogeneous coordinates makes it clear that this is just antipodal map...
{ "cite_spans": [] }
1807.11376
New Avenues for Einstein's Gravity: from Penrose's Twistors to Hitchin's Three-Forms
[ "Yannick Herfray" ]
[ "gr-qc", "hep-th", "math-ph", "math.MP" ]
2,018
en
Physics
[ -0.03498334810137749, 0.0006920925807207823, -0.03226649388670921, 0.015553243458271027, -0.002058629645034671, -0.04856763407588005, 0.0257338248193264, 0.048689741641283035, 0.034006502479314804, -0.009478473104536533, -0.027519624680280685, 0.002703501610085368, 0.004101996310055256, -0...
d6c9e30235f868c08f9f190e972b86aa5ff08e15
subsection
272
289
Kahler structure
As one dimensional complex projective space, the Riemann sphere has a natural SU(2)-invariant Kähler structure.\hspace*{-35.56593pt} J&= id\pi ^{A^{\prime }}\partial _{A^{\prime }} -i d\hat{\pi }^{A^{\prime }} \hat{\partial }_{A^{\prime }} = i d\zeta \partial _{\zeta } - i d\overline{\zeta }\partial _{\overline{\zeta }...
{ "cite_spans": [] }
1807.11376
New Avenues for Einstein's Gravity: from Penrose's Twistors to Hitchin's Three-Forms
[ "Yannick Herfray" ]
[ "gr-qc", "hep-th", "math-ph", "math.MP" ]
2,018
en
Physics
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416b4e3a0302316780fed078ebc4c9ca764bf185
subsection
273
289
Holomorphic line bundles over
A holomorphic vector bundle bundle is a complex vector bundle over a complex manifold such that the total space is a complex manifold and the projection operator is holomorphic. Practically, this is equivalent to the fact that transition functions between different trivialisations have to be holomorphic with respect to...
{ "cite_spans": [ { "arxiv_id": "", "doi": "", "end": 911, "openalex_id": "", "raw": "Huygbrechts, D. (2005). Complex Geometry - an introduction.", "source_ref_id": "11e3d334f718807e04b9b599a0588884ef7c88dc", "start": 537 }, { "arxiv_id": "", "doi": ""...
1807.11376
New Avenues for Einstein's Gravity: from Penrose's Twistors to Hitchin's Three-Forms
[ "Yannick Herfray" ]
[ "gr-qc", "hep-th", "math-ph", "math.MP" ]
2,018
en
Physics
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206828e34d231563929cc06b96e2c5ffe19aec9d
subsection
274
289
Holomorphic line bundles over
The most condensed definition uses of homogeneous coordinates:\mathcal {O}(n)S^{\prime }\times \left\lbrace \left( \pi ^{A^{\prime }}, \chi \right) \sim \left( \lambda \pi ^{A^{\prime }}, \lambda ^n\chi \right) \right\rbrace .Then the projection clearly is\begin{array}{ll} \Pi :& \left\lbrace \begin{array}{lll} \mathc...
{ "cite_spans": [] }
1807.11376
New Avenues for Einstein's Gravity: from Penrose's Twistors to Hitchin's Three-Forms
[ "Yannick Herfray" ]
[ "gr-qc", "hep-th", "math-ph", "math.MP" ]
2,018
en
Physics
[ -0.025422455742955208, 0.022263724356889725, -0.035341180860996246, -0.0022679546382278204, 0.018876098096370697, -0.02629225142300129, 0.007210150361061096, 0.009911095723509789, 0.04776247963309288, 0.05243190750479698, -0.035341180860996246, 0.016144633293151855, 0.021805936470627785, 0...
78a204424953da4e214b4f4a22b2e677c5e38215
subsection
275
289
Holomorphic line bundles over
Then the associated section is,s_f: \left\lbrace \begin{array}{lll} \mathbb {C}{P}^1&\rightarrow &\mathcal {O}(n) \\ \\ \left[\pi ^{A^{\prime }}\right] &\mapsto & \left[\pi ^{A^{\prime }},f\left( \pi ^{A^{\prime }}\right) \right]= \left[\lambda \pi ^{A^{\prime }},\lambda ^n f\left( p^{A^{\prime }}\right) \right]= \left...
{ "cite_spans": [] }
1807.11376
New Avenues for Einstein's Gravity: from Penrose's Twistors to Hitchin's Three-Forms
[ "Yannick Herfray" ]
[ "gr-qc", "hep-th", "math-ph", "math.MP" ]
2,018
en
Physics
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705d2a41189fe899009813ee636a5e864bc4c9bb
subsection
276
289
Holomorphic line bundles over
On the other hand there are no holomorphic global section of \mathcal {O}(n) for n<0.Some of these holomorphic line bundles are of particular importance and deserve a name:The "tautological bundle", \mathcal {O}(-1), is the natural line bundle over \mathbb {C}{P}^1 such that its total space identifies with S^{\prime }:...
{ "cite_spans": [] }
1807.11376
New Avenues for Einstein's Gravity: from Penrose's Twistors to Hitchin's Three-Forms
[ "Yannick Herfray" ]
[ "gr-qc", "hep-th", "math-ph", "math.MP" ]
2,018
en
Physics
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589f392a58dcb1be84f91429c270439a65bb94b2
subsection
277
289
Holomorphic line bundles over
This is better seen in charts:llllllllllll : {{llc} \mapsto & \Pi ^{-1}\left( U\right)\\ \left( \zeta , \chi \right) &\mapsto & \left( \zeta , \chi \partial _{\zeta } \right). ,        ': {{llc} \mapsto & \Pi ^{-1}\left( U^{\prime }\right)\subset S^{\prime }\\ \left( \zeta ^{\prime }, \chi ^{\prime }\right) &\mapsto & ...
{ "cite_spans": [] }
1807.11376
New Avenues for Einstein's Gravity: from Penrose's Twistors to Hitchin's Three-Forms
[ "Yannick Herfray" ]
[ "gr-qc", "hep-th", "math-ph", "math.MP" ]
2,018
en
Physics
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ea91dd9f8ce601bbee6035210ac5dd06b71d3efc
subsection
278
289
Hermitian metric on the
The total space of the \mathcal {O}(-1)line bundle \Pi :S^{\prime } \mapsto \mathbb {C}{P}^1 being equipped with an hermitian metric, g=\frac{1}{2} d\pi _{A^{\prime }}\odot d\hat{\pi }^{A^{\prime }} it induces a metric on the fibers. This is done by restricting g to the vertical tangent subspace \mathcal {V}:\mathcal {...
{ "cite_spans": [] }
1807.11376
New Avenues for Einstein's Gravity: from Penrose's Twistors to Hitchin's Three-Forms
[ "Yannick Herfray" ]
[ "gr-qc", "hep-th", "math-ph", "math.MP" ]
2,018
en
Physics
[ -0.028963232412934303, 0.03143533319234848, -0.02672003209590912, 0.023133961483836174, 0.004379582591354847, -0.06763174384832382, -0.00925511121749878, -0.001185501110740006, 0.046328965574502945, 0.03010772354900837, -0.05166991800069809, 0.024415791034698486, 0.0290547925978899, -0.008...
e1161ab3a0ed149c591257890892260d50546943
subsection
279
289
Covariant derivative on
We now introduce the Chern connection associated with the Hermitian metric (REF ):a_{(n)} = -n \;\frac{\overline{\zeta }}{1+\zeta \overline{\zeta }}d\zeta .If \alpha ^{\prime }(\zeta ) is any \mathcal {O}(n,m)-valued k-form on \mathbb {C}{P}^1, then from (REF ), we can define its covariant derivative asd_a \alpha ^{\pr...
{ "cite_spans": [] }
1807.11376
New Avenues for Einstein's Gravity: from Penrose's Twistors to Hitchin's Three-Forms
[ "Yannick Herfray" ]
[ "gr-qc", "hep-th", "math-ph", "math.MP" ]
2,018
en
Physics
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3a890d2da21e2a0e3e6ade695b8e93ae70a65bfd
subsection
280
289
Chern connection
The connection (REF ) has the following property: it is compatible with the complex structure, in the sense that a_{(n)}\Big |_{T^{(0,1)}}=0. It is also compatible with the Hermitian metric (REF ) in the sense thatd_{a} h_{n}= d\left(\left(1+\zeta \overline{\zeta }\right)^{-n} \right) + \left( a_{(n)}+\overline{a}_{(n)...
{ "cite_spans": [ { "arxiv_id": "", "doi": "", "end": 665, "openalex_id": "", "raw": "Huygbrechts, D. (2005). Complex Geometry - an introduction.", "source_ref_id": "11e3d334f718807e04b9b599a0588884ef7c88dc", "start": 142 } ] }
1807.11376
New Avenues for Einstein's Gravity: from Penrose's Twistors to Hitchin's Three-Forms
[ "Yannick Herfray" ]
[ "gr-qc", "hep-th", "math-ph", "math.MP" ]
2,018
en
Physics
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290fb14ddb3988e4944f30f713b95d9c294cee6a
subsection
281
289
The Twistor Space of Complexified Anti-Self-Dual Space-Times
We here review how to construct the twistor space M) of an anti-self-dual complexified space-time (cf , for the original references, , for pedagogical presentations). We especially emphasise how the self-dual connection D= d + A on space-time gives a \mathcal {O}(2)-valued one-form \tau on the associated twistor space....
{ "cite_spans": [ { "arxiv_id": "", "doi": "10.1007/bf00762011", "end": 167, "openalex_id": "https://openalex.org/W2091099245", "raw": "Penrose, R. (1976). Nonlinear Gravitons and Curved Twistor Theory. Gen.Rel.Grav., 7:31–52.", "source_ref_id": "c4f48238507e5122f434fae4d971d76...
1807.11376
New Avenues for Einstein's Gravity: from Penrose's Twistors to Hitchin's Three-Forms
[ "Yannick Herfray" ]
[ "gr-qc", "hep-th", "math-ph", "math.MP" ]
2,018
en
Physics
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79ddee881175a3c2c7100204ca04facef44dbf69
subsection
282
289
The Twistor Space of Complexified Anti-Self-Dual Space-Times
We note \Pi \colon \mathbb {PF}(M) \rightarrow \mathbb {PT}(M) the projection operator.We then have the classical double fibration picture:x1) \mathbb {PF}(M); x2) [left = 2cm of x1] ; x3) [right = 2cm of x1];y2) [below = 1.5cm of x2] \mathbb {PT}(M); y3) [below = 1.5cm of x3] M;[<-] (y2) – node[left,pos=0.6]\Pi (x1) ;...
{ "cite_spans": [] }
1807.11376
New Avenues for Einstein's Gravity: from Penrose's Twistors to Hitchin's Three-Forms
[ "Yannick Herfray" ]
[ "gr-qc", "hep-th", "math-ph", "math.MP" ]
2,018
en
Physics
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200fd0fdb9054df6a9d6858083f6d5f39227824d
subsection
283
289
The Twistor Space of Complexified Anti-Self-Dual Space-Times
A tangent vector to p then corresponds to a certain vector field on \hat{p} that “connects" \hat{p} to an other infinitesimally close integral surface :X(x) = V(x){}^{AA^{\prime }} D_{AA^{\prime }} + \beta (x){}^{B^{\prime }} \frac{\partial }{\partial \pi ^{B^{\prime }}}Being a “connecting vector field", it is defined ...
{ "cite_spans": [] }
1807.11376
New Avenues for Einstein's Gravity: from Penrose's Twistors to Hitchin's Three-Forms
[ "Yannick Herfray" ]
[ "gr-qc", "hep-th", "math-ph", "math.MP" ]
2,018
en
Physics
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86cfb8d1c1a47d70a0e16dde331413f4905baf08
subsection
284
289
The Twistor Space of Complexified Anti-Self-Dual Space-Times
Contracting this form with the connecting vector field (REF ) we get a scalar field on \hat{p},\tau (X) = \beta _{A^{\prime }}\pi ^{A^{\prime }}.Now \tau defines a one-form on M) if and only if this scalar field is constant along \hat{p} i.e\pi ^{A^{\prime }}\nabla _{AA^{\prime }} \left( \tau (X) \right) =0.Making use ...
{ "cite_spans": [] }
1807.11376
New Avenues for Einstein's Gravity: from Penrose's Twistors to Hitchin's Three-Forms
[ "Yannick Herfray" ]
[ "gr-qc", "hep-th", "math-ph", "math.MP" ]
2,018
en
Physics
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0044572a0137974253424a6f38a7962862c7e981
subsection
285
289
3d Gravity Conventions
In this section, we review some basic facts about 3D gravity. Our notations are standard for the gravity literature.
{ "cite_spans": [] }
1807.11376
New Avenues for Einstein's Gravity: from Penrose's Twistors to Hitchin's Three-Forms
[ "Yannick Herfray" ]
[ "gr-qc", "hep-th", "math-ph", "math.MP" ]
2,018
en
Physics
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1065d878162f9d9c4855ade662fcd26bd42b0749
subsection
286
289
Einstein-Cartan frame formalism in 3D
Let \left(e^{i}\right)_{i\in \lbrace 1,2,3\rbrace } be orthogonal frame field so that the 3D metric isds^2 =e^i \otimes e^j \eta _{ij},where \eta _{ij}={\rm diag}(1,1,1). We raise and lower indices with the metric \delta _{ij}, and the spin-connection is the set of one-forms w^{ij}=w^{[ij]}. The anti-symmetry is the st...
{ "cite_spans": [] }
1807.11376
New Avenues for Einstein's Gravity: from Penrose's Twistors to Hitchin's Three-Forms
[ "Yannick Herfray" ]
[ "gr-qc", "hep-th", "math-ph", "math.MP" ]
2,018
en
Physics
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3a015a61e38466c8c1d1abc25ba1099907f5126c
subsection
287
289
Matrix notations
It is very convenient to get rid of the internal i,j,\ldots indices at the expense of making all objects \mathfrak {su}(2)-valued. The Lie algebra generators \left(\sigma ^{i}\right)_{i \in \lbrace 1,2,3\rbrace } are taken such that they satisfy\textrm {Tr}(\sigma _i \sigma _j) = - \frac{1}{2} \delta _{ij}, \qquad [\si...
{ "cite_spans": [] }
1807.11376
New Avenues for Einstein's Gravity: from Penrose's Twistors to Hitchin's Three-Forms
[ "Yannick Herfray" ]
[ "gr-qc", "hep-th", "math-ph", "math.MP" ]
2,018
en
Physics
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a8f1b4c0f1e8533548c6509074ff1bbbb03a160d
subsection
288
289
Chern-Simons formulation
The two sets of equations \nabla {{e}}=0, {{f}}={{e}}\wedge {{e}} can be combined as the real and imaginary parts of a single complex-valued equation by introducing \mathfrak {sl}(2,-valued fields{{a}}_{\pm } {{w}}\pm \sqrt{\Lambda } {{e}}.Here and in what follows \sqrt{\Lambda } will stand for i\sqrt{|\Lambda |} when ...
{ "cite_spans": [] }
1807.11376
New Avenues for Einstein's Gravity: from Penrose's Twistors to Hitchin's Three-Forms
[ "Yannick Herfray" ]
[ "gr-qc", "hep-th", "math-ph", "math.MP" ]
2,018
en
Physics
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bffb50c1e5d3ba29af695cfa91940f6dc530ee76
abstract
0
20
Abstract
Both humans and the sensors on an autonomous vehicle have limited sensing capabilities. When these limitations coincide with scenarios involving vulnerable road users, it becomes important to account for these limitations in the motion planner. For the scenario of an occluded pedestrian crosswalk, the speed of the appr...
{ "cite_spans": [] }
1802.06314
Autonomous Vehicle Speed Control for Safe Navigation of Occluded Pedestrian Crosswalk
[ "Sarah Thornton" ]
[ "cs.RO", "cs.AI", "cs.SY" ]
2,018
en
Computer Science
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186e31c8f5b9761945ed623c4abc991765637ef5
subsection
1
20
Introduction
Autonomous vehicles rely on sensors to provide information about the world to decision-making algorithms. Just like humans have limited sensing capabilities, the sensors on an autonomous vehicle are also susceptible to limitations. GPS requires open skies. Cameras require certain weather and lighting conditions. Radar,...
{ "cite_spans": [] }
1802.06314
Autonomous Vehicle Speed Control for Safe Navigation of Occluded Pedestrian Crosswalk
[ "Sarah Thornton" ]
[ "cs.RO", "cs.AI", "cs.SY" ]
2,018
en
Computer Science
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67cbb8392524dc9b5956af9c0a3d02748a6c1176
subsection
2
20
Related Work
Motion planning under uncertainty is a large topic of study in the robotics community. For an autonomous vehicle, motion planning encompasses both lateral and longitudinal motion which are controlled through a combination of steering and acceleration. A sampled-based motion planning technique known as Rapidly-Exploring...
{ "cite_spans": [] }
1802.06314
Autonomous Vehicle Speed Control for Safe Navigation of Occluded Pedestrian Crosswalk
[ "Sarah Thornton" ]
[ "cs.RO", "cs.AI", "cs.SY" ]
2,018
en
Computer Science
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126e0b1bf0c498bb34972e6ea9a4bf1a2fd1a46d
subsection
3
20
Infrastructure
For this work, the simulation environment is two-fold. The first part is a nonlinear vehicle dynamic model that simulates vehicle pose information and how the vehicle maneuvers in space. The other aspect is the simulation of the occupancy grid.
{ "cite_spans": [] }
1802.06314
Autonomous Vehicle Speed Control for Safe Navigation of Occluded Pedestrian Crosswalk
[ "Sarah Thornton" ]
[ "cs.RO", "cs.AI", "cs.SY" ]
2,018
en
Computer Science
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203f077a290a7a6beef024e743c48272c0428d41
subsection
4
20
Vehicle Motion
A vehicle is controlled by commanding a steer angle (\delta ) and longitudinal acceleration (a_{\text{x}}). The vehicle motion is simulated using a lumped axle vehicle model, where the two front tires are lumped as one front tire and the two rear tires are lumped as one rear tire (also known as a bicycle or single-trac...
{ "cite_spans": [] }
1802.06314
Autonomous Vehicle Speed Control for Safe Navigation of Occluded Pedestrian Crosswalk
[ "Sarah Thornton" ]
[ "cs.RO", "cs.AI", "cs.SY" ]
2,018
en
Computer Science
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6875bf55c7fb2db7e63acfc8a9d5fa2a4003f4ca
subsection
5
20
Occupancy Grid
The occupancy grid is a discretized top-down view of the world around the vehicle. To emulate the Velodyne HDL-32E lidar, the longitudinal range of the occupancy grid is limited to 70 in front of the vehicle. Because the width of the roadway in the scenario is much less than the range of the lidar, the lateral range of...
{ "cite_spans": [] }
1802.06314
Autonomous Vehicle Speed Control for Safe Navigation of Occluded Pedestrian Crosswalk
[ "Sarah Thornton" ]
[ "cs.RO", "cs.AI", "cs.SY" ]
2,018
en
Computer Science
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e64db6f7e3b2aba5da29f37c12555e2525ccc452
subsection
6
20
POMDP
A POMDP makes decisions based on the history of observations o_{1:t}. To reduce the information stored, the history is summarized in a belief state b, which is a distribution over states. The optimal policy is represented as a set of alpha vectors, which convert the belief state to an action. A POMDP model takes a simi...
{ "cite_spans": [] }
1802.06314
Autonomous Vehicle Speed Control for Safe Navigation of Occluded Pedestrian Crosswalk
[ "Sarah Thornton" ]
[ "cs.RO", "cs.AI", "cs.SY" ]
2,018
en
Computer Science
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99e285f89c81c8f5d78c8c47a066f496c86a02ee
subsection
7
20
State Space
The state space is represented in a low dimensional subspace that captures pose and motion of the vehicle as well as perception information. The components of the state considered in this work are:V: current velocity of the vehicle D: distance along the path C: event of pedestrian crossingSpeed and distance along the...
{ "cite_spans": [] }
1802.06314
Autonomous Vehicle Speed Control for Safe Navigation of Occluded Pedestrian Crosswalk
[ "Sarah Thornton" ]
[ "cs.RO", "cs.AI", "cs.SY" ]
2,018
en
Computer Science
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f0e2257aef9834c5c6ed32e390992b46613a6599
subsection
8
20
Action Space
The vehicle actuation considered here is longitudinal acceleration. Commanded longitudinal acceleration is determined by proportional speed control. Thus, the POMDP action space is a speed scaling factor applied to the desired speed in the longitudinal control. After discretization of the action space, the actions are ...
{ "cite_spans": [] }
1802.06314
Autonomous Vehicle Speed Control for Safe Navigation of Occluded Pedestrian Crosswalk
[ "Sarah Thornton" ]
[ "cs.RO", "cs.AI", "cs.SY" ]
2,018
en
Computer Science
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96f51e86623044b186d56323a27b20e9f09f312f
subsection
9
20
Observation Space
The observation space captures information the agent observes after taking an action. In this work, the observations are provided just from the lidar sensors. Two types of observations are considered:N: number of unobservable tiles C: detection of pedestrian crossingTo simplify the problem size, the number of unobserv...
{ "cite_spans": [] }
1802.06314
Autonomous Vehicle Speed Control for Safe Navigation of Occluded Pedestrian Crosswalk
[ "Sarah Thornton" ]
[ "cs.RO", "cs.AI", "cs.SY" ]
2,018
en
Computer Science
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b80aafde2933be22b1cd8a2e9c9d6f563e635e2e
subsection
10
20
Reward Model
The reward function in this POMDP formulation is designed with the following objectives in mind:Encourage the vehicle to drive to the end of the path. If a pedestrian is detected, then the vehicle should yield to the pedestrian. Thus, non-zero scale factors are penalized when a pedestrian crossing event is true. Addi...
{ "cite_spans": [] }
1802.06314
Autonomous Vehicle Speed Control for Safe Navigation of Occluded Pedestrian Crosswalk
[ "Sarah Thornton" ]
[ "cs.RO", "cs.AI", "cs.SY" ]
2,018
en
Computer Science
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0108d6eeccb05ab1428ec2ba098e1857a26dbedf
subsection
11
20
State-Transition Model
The dynamics of the system are not actually stochastic, but rather uncertainty is introduced from the crude discretization of the state space. Also, the event of a pedestrian crossing is modeled as a random process. The following parameters characterize the state-transition model:Speed scaling and changes in speed are ...
{ "cite_spans": [] }
1802.06314
Autonomous Vehicle Speed Control for Safe Navigation of Occluded Pedestrian Crosswalk
[ "Sarah Thornton" ]
[ "cs.RO", "cs.AI", "cs.SY" ]
2,018
en
Computer Science
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a6027392e04c26865ea598b48a3a966a29856faa
subsection
12
20
Observation Model
In a typical POMDP problem, the observation model is defined as the conditional probability of observing each observation o given the current state s and the action a taken to get there: Pr(o|s,a). For this work, it is assumed the action does not contribute to the observation o given s. Thus, the dependence on a is dro...
{ "cite_spans": [] }
1802.06314
Autonomous Vehicle Speed Control for Safe Navigation of Occluded Pedestrian Crosswalk
[ "Sarah Thornton" ]
[ "cs.RO", "cs.AI", "cs.SY" ]
2,018
en
Computer Science
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25dad6a5a362494b87c1fd08ba28b9750d67f390
subsection
13
20
QMDP
QMDP is an offline method to approximate an optimal POMDP solution, and assumes at the next time step the state will be fully observable. QMDP is well suited for this problem because the actions are not information gathering. The algorithm is akin to value iteration for MDP, except it iterates over the belief state. Th...
{ "cite_spans": [] }
1802.06314
Autonomous Vehicle Speed Control for Safe Navigation of Occluded Pedestrian Crosswalk
[ "Sarah Thornton" ]
[ "cs.RO", "cs.AI", "cs.SY" ]
2,018
en
Computer Science
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2b1407c368252adb40c0d762bde900fa8d6b9372
subsection
14
20
Policy Execution
The execution of the POMDP policy follows Algorithm REF . The belief state is initialized to a uniform distribution. Using the current belief state, an optimal action is calculated using the set of alpha vectors and is executed in the vehicle longitudinal control. In the next control loop (not represented in Algorithm ...
{ "cite_spans": [] }
1802.06314
Autonomous Vehicle Speed Control for Safe Navigation of Occluded Pedestrian Crosswalk
[ "Sarah Thornton" ]
[ "cs.RO", "cs.AI", "cs.SY" ]
2,018
en
Computer Science
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a8dee112db0ffda533fc3c791fcd5e96570ef006
subsection
15
20
Evaluation Framework
To evaluate the POMDP approach for speed control in an uncertain environment, an oracle approach and baseline approach are also implemented.
{ "cite_spans": [] }
1802.06314
Autonomous Vehicle Speed Control for Safe Navigation of Occluded Pedestrian Crosswalk
[ "Sarah Thornton" ]
[ "cs.RO", "cs.AI", "cs.SY" ]
2,018
en
Computer Science
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42cad407c79b95b212b72b0cffde5445ac32595a
subsection
16
20
Oracle
The oracle approach does not use unobservable information from the occupancy grid. Instead, perfect sensing is assumed and exact pose information about the scenario is used to allow the autonomous vehicle to maneuver around the parked vehicle at the speed limit since it will also know with perfect knowledge whether a p...
{ "cite_spans": [] }
1802.06314
Autonomous Vehicle Speed Control for Safe Navigation of Occluded Pedestrian Crosswalk
[ "Sarah Thornton" ]
[ "cs.RO", "cs.AI", "cs.SY" ]
2,018
en
Computer Science
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dcdebfb225b2ea442dfbe42b2d833ab5b6a3968a
subsection
17
20
Baseline
The baseline speed scale factor is determined by a simple function inversely proportional to the number of unobservable tiles. The speed scale factor is discretized into 10 bins, where a scale factor of 1.0 means the number of unobservable spaces is negligible and the vehicle can maneuver at the desired speed and a sca...
{ "cite_spans": [] }
1802.06314
Autonomous Vehicle Speed Control for Safe Navigation of Occluded Pedestrian Crosswalk
[ "Sarah Thornton" ]
[ "cs.RO", "cs.AI", "cs.SY" ]
2,018
en
Computer Science
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f00bda3ba6d8317b1acb1eabe306deb54478b4cc
subsection
18
20
Simulation Results
The examples for comparison are a pedestrian hidden behind the occluded vehicle in the pedestrian crosswalk (Fig. REF ), and a pedestrian in the crosswalk not behind the occluding vehicle (Fig. REF ). Since the pedestrian is in the crosswalk, all vehicles must yield. However, if an approach is unable to account for a p...
{ "cite_spans": [] }
1802.06314
Autonomous Vehicle Speed Control for Safe Navigation of Occluded Pedestrian Crosswalk
[ "Sarah Thornton" ]
[ "cs.RO", "cs.AI", "cs.SY" ]
2,018
en
Computer Science
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54adffcac9e024849168f30b1ac252a5cf229869
subsection
19
20
Conclusions
The preliminary results presented above demonstrate how well the baseline and oracle approaches work. Next steps are to keep improving the POMDP problem formulation. In particular, the observation model needs to be improved. Running many simulations with the pedestrian randomly placed throughout the crosswalk should al...
{ "cite_spans": [] }
1802.06314
Autonomous Vehicle Speed Control for Safe Navigation of Occluded Pedestrian Crosswalk
[ "Sarah Thornton" ]
[ "cs.RO", "cs.AI", "cs.SY" ]
2,018
en
Computer Science
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7cb32234e1ed54000cbc6fcdc61e2398ee1d68a6
abstract
0
13
Abstract
Observational tests of stellar and Galactic chemical evolution call for the joint knowledge of a star's physical parameters, detailed element abundances, and precise age. For cool main-sequence (MS) stars the abundances of many elements can be measured from spectroscopy, but ages are very hard to determine. The situati...
{ "cite_spans": [] }
10.3847/1538-4357/aaee74
1802.06663
Precise Ages of Field Stars from White Dwarf Companions
[ "M. Fouesneau", "H. -W. Rix", "T. von Hippel", "D. W. Hogg", "H. Tian" ]
[ "astro-ph.SR" ]
2,018
en
Physics
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192e016f4473cc32d393eec7bfd1775f9e55342f
subsection
1
13
Introduction
The two members of a binary star systems are stars born at nearly the same time from the material of the same element composition, but usually with different masses. Binary stars are not only interesting in themselves but offer a wide range of avenues to measure stellar properties and learn about stellar physics. These...
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10.3847/1538-4357/aaee74
1802.06663
Precise Ages of Field Stars from White Dwarf Companions
[ "M. Fouesneau", "H. -W. Rix", "T. von Hippel", "D. W. Hogg", "H. Tian" ]
[ "astro-ph.SR" ]
2,018
en
Physics
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3d5f99ca6b43ba9297f7853c10655a93a4ed1ecd
subsection
2
13
Introduction
In this regime, WD-MS wide binaries may be the best way forward to reach \sim 10\% age precision.This paper is organized as follows: in Section  we describe the identification of likely WD-MS binary systems that have TGAS information on the MS component; in Section  we then exploit the resulting precise luminosity info...
{ "cite_spans": [] }
10.3847/1538-4357/aaee74
1802.06663
Precise Ages of Field Stars from White Dwarf Companions
[ "M. Fouesneau", "H. -W. Rix", "T. von Hippel", "D. W. Hogg", "H. Tian" ]
[ "astro-ph.SR" ]
2,018
en
Physics
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8f6cc5bb0b89dd4ba118dfd86f6a78d451a41da9
subsection
3
13
Identification of Candidate WD - MS Wide Binaries
We aim to identify WD-MS wide binary candidates without using the actual luminosity (or apparent magnitude) or detailed color of the possible WD component, as these quantities should subsequently serve as constraints on the WD's age. We cannot also rely on only spectroscopically confirmed WDs, as this would severely li...
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10.3847/1538-4357/aaee74
1802.06663
Precise Ages of Field Stars from White Dwarf Companions
[ "M. Fouesneau", "H. -W. Rix", "T. von Hippel", "D. W. Hogg", "H. Tian" ]
[ "astro-ph.SR" ]
2,018
en
Physics
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3bddcbfedfe67dc6a9278e71b7f9cf253809db4e
subsection
4
13
Identification of Candidate WD - MS Wide Binaries
The specifics are detailed in Appendix .This above selection left us with a wide binary sample of about 150 objects, where we expect the companions to the TGAS MS stars to be either fainter MS stars or WDs. Adopting the parallax-distance to the primary MS, we can construct a color – absolute magnitude diagram for the c...
{ "cite_spans": [] }
10.3847/1538-4357/aaee74
1802.06663
Precise Ages of Field Stars from White Dwarf Companions
[ "M. Fouesneau", "H. -W. Rix", "T. von Hippel", "D. W. Hogg", "H. Tian" ]
[ "astro-ph.SR" ]
2,018
en
Physics
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913b17594fdafc01b58f9678c07446984c69c48a
subsection
5
13
Age Constraints on the Wide Binary Systems
We are now left with a set of 91 candidate WDs (cWD), whose distances are precisely constrained by the parallaxes to their companions. Of those, 15 are brighter (Figure REF , red circles) than the predictions from the 0.5\,{\rm M}_\odot cooling curve of , which implies they have masses that are too low to be consisten...
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10.3847/1538-4357/aaee74
1802.06663
Precise Ages of Field Stars from White Dwarf Companions
[ "M. Fouesneau", "H. -W. Rix", "T. von Hippel", "D. W. Hogg", "H. Tian" ]
[ "astro-ph.SR" ]
2,018
en
Physics
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6d20cbb601a3aff404db1ca49bb0af4785933c38
subsection
6
13
Age Constraints on the Wide Binary Systems
Without spectroscopy, we do not know which objects are H-atmosphere (DA) WDs and which are DBs. Fortunately for our analysis, nature makes predominantly DA WDs (\sim 75%; ), and it is therefore a good initial assumption that those cWDs that have posterior distance probabilities consistent with their candidate MS compan...
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10.3847/1538-4357/aaee74
1802.06663
Precise Ages of Field Stars from White Dwarf Companions
[ "M. Fouesneau", "H. -W. Rix", "T. von Hippel", "D. W. Hogg", "H. Tian" ]
[ "astro-ph.SR" ]
2,018
en
Physics
[ -0.010412875562906265, -0.00541622145101428, -0.07573555409908295, -0.010298448614776134, -0.03371788561344147, -0.030407123267650604, 0.027386246249079704, -0.0017535969382151961, 0.028667829930782318, 0.028179606422781944, -0.030407123267650604, -0.013258298859000206, -0.010283191688358784...
067d1ce4e5f7781bab99dc5618a91c1eb8c62c2b
subsection
7
13
Age Constraints on the Wide Binary Systems
For WDs with {T}_{\rm eff}\le 5000 K, issues arise both in our present understanding of their atmospheres and possibly with additional sources of energy release during crystallization . We can avoid most of these problems by focusing on the WDs in a suitable mass and temperature range. Nevertheless, formal tests on WD ...
{ "cite_spans": [ { "arxiv_id": "", "doi": "", "end": 185, "openalex_id": "", "raw": "Horowitz, C. J., Schneider, A. S., & Berry, D. K. 2010, Physical Review Letters, 104, 231101", "source_ref_id": "8b726df4bd4284d448e93e2cd6153063acdc0ba4", "start": 0 } ] }
10.3847/1538-4357/aaee74
1802.06663
Precise Ages of Field Stars from White Dwarf Companions
[ "M. Fouesneau", "H. -W. Rix", "T. von Hippel", "D. W. Hogg", "H. Tian" ]
[ "astro-ph.SR" ]
2,018
en
Physics
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477254ce47479a1c7d519248167071b37b05e9e0
subsection
8
13
Discussion and Outlook
In this paper we carried out a pilot study for one of the many applications of using Gaia data to constrain stellar properties. We identified systems where Gaia parallaxes gave us distances to nearby (<200\,\rm pc) main sequence stars, and where common proper motion information from the GPS1 catalog provided strong evi...
{ "cite_spans": [] }
10.3847/1538-4357/aaee74
1802.06663
Precise Ages of Field Stars from White Dwarf Companions
[ "M. Fouesneau", "H. -W. Rix", "T. von Hippel", "D. W. Hogg", "H. Tian" ]
[ "astro-ph.SR" ]
2,018
en
Physics
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2bc9cc8fed85b157f2544c7dbfd81cc9740f75a3
subsection
9
13
GPS1
In this section, we detail the selection query we performed on TGAS and GPS1 catalogs.Matching GPS1 against TGAS will report all the stars from GPS1 within some radius that could potentially be associated with a TGAS bright star. If we also filter on parallax and motion similarity this will only give co-moving pairs. W...
{ "cite_spans": [] }
10.3847/1538-4357/aaee74
1802.06663
Precise Ages of Field Stars from White Dwarf Companions
[ "M. Fouesneau", "H. -W. Rix", "T. von Hippel", "D. W. Hogg", "H. Tian" ]
[ "astro-ph.SR" ]
2,018
en
Physics
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c22e11767443c8f25955518d917b6c6fc2e14ea3
subsection
10
13
GPS1
Finally, we also added color terms that avoid having main-sequence objects and we also select good photometry for their SED analysis. Based on empirical definitions we added the following selections:\begin{split} & \left|(g - i) -1.6 \times (g - r) + 0.1 \right| < 0.15\, \mathrm {mag},\\ & \left(\sigma _g,\, \sigma _r ...
{ "cite_spans": [] }
10.3847/1538-4357/aaee74
1802.06663
Precise Ages of Field Stars from White Dwarf Companions
[ "M. Fouesneau", "H. -W. Rix", "T. von Hippel", "D. W. Hogg", "H. Tian" ]
[ "astro-ph.SR" ]
2,018
en
Physics
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2ce3f20bc8fa343269534ebc00739b76b6019e40
subsection
11
13
GPS1
As GAVO is currently the only service providing the GPS1 catalog, the field names correspond to their definition, and may vary when using other sources (e.g., VizieR, Gaia Archive).SELECTdb.obj_id, db.ra, db.dec, db.e_ra, db.e_dec, db.pmra, db.e_pmra,db.pmde, db.e_pmde, db.magg,  db.e_magg, db.magr,  db.e_magr,db.magi,...
{ "cite_spans": [] }
10.3847/1538-4357/aaee74
1802.06663
Precise Ages of Field Stars from White Dwarf Companions
[ "M. Fouesneau", "H. -W. Rix", "T. von Hippel", "D. W. Hogg", "H. Tian" ]
[ "astro-ph.SR" ]
2,018
en
Physics
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9ee80fbbdff16fe28826059f7f8a52bbe4b41c78
subsection
12
13
Catalogs
In this section we describe the content of the catalog generated during this study.The catalog contains the photometric and astrometric data for all of the WD candidates of this study. For each star, we also provide the mean, median and standard deviation of the posterior PDF of the WD properties, esp. age and ZAMS mas...
{ "cite_spans": [] }
10.3847/1538-4357/aaee74
1802.06663
Precise Ages of Field Stars from White Dwarf Companions
[ "M. Fouesneau", "H. -W. Rix", "T. von Hippel", "D. W. Hogg", "H. Tian" ]
[ "astro-ph.SR" ]
2,018
en
Physics
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0ecceae7904b9e3832efdc3eb9374df9861de6ab
abstract
0
13
Abstract
Understanding the mechanisms of neural communication in large-scale brain networks remains a major goal in neuroscience. We investigated whether navigation is a parsimonious routing model for connectomics. Navigating a network involves progressing to the next node that is closest in distance to a desired destination. W...
{ "cite_spans": [] }
10.1073/pnas.1801351115
1801.07938
Navigation of brain networks
[ "Caio Seguin", "Martijn P. van den Heuvel", "Andrew Zalesky" ]
[ "q-bio.NC" ]
2,018
en
Quantitative Biology
[ -0.045731838792562485, -0.020135432481765747, -0.010960082523524761, -0.008221968077123165, -0.026298094540834427, 0.01905239000916481, 0.019494760781526566, -0.024070994928479195, -0.0038840791676193476, 0.027472661808133125, -0.0006969224195927382, -0.014262598007917404, 0.0071274857036769...
149247add2faa1ec3267695ed5e73c409f6a0261
subsection
1
13
Overview
This supporting document provides details on the acquisition and preprocessing of the analyzed connectivity data. We also provide descriptions of the network measures and methods applied throughout this work. Finally, we include supplementary and replication analyses that indicate the robustness and universality of the...
{ "cite_spans": [] }
10.1073/pnas.1801351115
1801.07938
Navigation of brain networks
[ "Caio Seguin", "Martijn P. van den Heuvel", "Andrew Zalesky" ]
[ "q-bio.NC" ]
2,018
en
Quantitative Biology
[ -0.02375972829759121, 0.026582816615700722, -0.06873077154159546, 0.009728211909532547, -0.015626179054379463, -0.024278566241264343, 0.015015781857073307, 0.032290033996105194, 0.0031511776614934206, 0.01637391559779644, -0.037386853247880936, -0.00898047536611557, -0.00666859420016408, 0...
a6cde848730f7b256a266795b25d79fae7165868
subsection
2
13
Mouse.
The Allen Institute for Brain Science mapped the mesoscale topology of the mouse nervous system by means of anterograde axonal injections of a viral tracer . Using two-photon tomography, they identified axonal projections from the 469 injections sites to 295 target regions. Building on these efforts, Rubinov and collea...
{ "cite_spans": [ { "arxiv_id": "", "doi": "10.1038/nature13186", "end": 157, "openalex_id": "https://openalex.org/W1975389666", "raw": "S. W. Oh, J. A. Harris, L. Ng, B. Winslow, N. Cain, S. Mihalas, Q. Wang, C. Lau, L. Kuan, A. M. Henry, M. T. Mortrud, B. Ouellette, T. N. Nguyen, S...
10.1073/pnas.1801351115
1801.07938
Navigation of brain networks
[ "Caio Seguin", "Martijn P. van den Heuvel", "Andrew Zalesky" ]
[ "q-bio.NC" ]
2,018
en
Quantitative Biology
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18ef9ec0ea46b6f4bdd6fdcfcb4702220f3ddddb
subsection
3
13
Macaque.
Markov and colleagues applied 1615 retrograde tracer injections to 29 of the 91 areas of the macaque cerebral cortex, spanning occipital, temporal, parietal, frontal, prefrontal and limbic regions , . This resulted in a 29 \times 29 directed interregional sub-network of the macaque coritco-cortical connections. Connect...
{ "cite_spans": [ { "arxiv_id": "", "doi": "10.1073/pnas.1218972110", "end": 200, "openalex_id": "https://openalex.org/W2145631310", "raw": "N. T. Markov, M. Ercsey-Ravasz, C. Lamy, A. R. Ribeiro Gomes, L. Magrou, P. Misery, P. Giroud, P. Barone, C. Dehay, Z. Toroczkai, K. Knoblauch,...
10.1073/pnas.1801351115
1801.07938
Navigation of brain networks
[ "Caio Seguin", "Martijn P. van den Heuvel", "Andrew Zalesky" ]
[ "q-bio.NC" ]
2,018
en
Quantitative Biology
[ -0.00041005908860825, -0.0522129200398922, -0.016005655750632286, -0.021681634709239006, -0.00008773356967139989, 0.0015134040731936693, 0.008437681011855602, -0.027372874319553375, 0.03048550896346569, 0.014220467768609524, 0.0012006148463115096, 0.01050514169037342, -0.0031717594247311354,...
d583b4edc5ec6149388f70e98933c5fe0de7df4f
subsection
4
13
Human data acquisition and preprocessing.
Minimally preprocessed diffusion weighted MRI data from 75 unrelated healthy participants (age 22–35, 40 females) was obtained from the Human Connectome Project (HCP) HCP participants ID: 100206, 100307, 100408, 101006, 101107, 101309, 101915, 102109, 102513, 102614, 102715, 102816, 103111, 103212, 103414, 103515, 1038...
{ "cite_spans": [ { "arxiv_id": "", "doi": "10.1016/j.neuroimage.2013.05.041", "end": 789, "openalex_id": "https://openalex.org/W2024729467", "raw": "D. C. Van Essen, S. M. Smith, D. M. Barch, T. E. J. Behrens, E. Yacoub, K. Ugurbil, and WU-Minn HCP Consortium, “The wu-minn human con...
10.1073/pnas.1801351115
1801.07938
Navigation of brain networks
[ "Caio Seguin", "Martijn P. van den Heuvel", "Andrew Zalesky" ]
[ "q-bio.NC" ]
2,018
en
Quantitative Biology
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717a295c24e9c99cfceaac25fb25a6debddc054c
subsection
5
13
Human cortical parcellation.
Connectome analyses are sensitive to the number of nodes used to reconstruct brain networks . In order to assess the validity of our results across connectomes defined over different granularities of cortical segmentations, we generated parcellations of the human cerebral cortex containing N=256,512,1024 regions. In ad...
{ "cite_spans": [ { "arxiv_id": "", "doi": "10.1016/j.neuroimage.2009.12.027", "end": 93, "openalex_id": "https://openalex.org/W2136395604", "raw": "A. Zalesky, A. Fornito, I. H. Harding, L. Cocchi, M. Yücel, C. Pantelis, and E. T. Bullmore, “Whole-brain anatomical networks: does the...
10.1073/pnas.1801351115
1801.07938
Navigation of brain networks
[ "Caio Seguin", "Martijn P. van den Heuvel", "Andrew Zalesky" ]
[ "q-bio.NC" ]
2,018
en
Quantitative Biology
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fbe97a29bbc3e0bcfe952139e8cdd00c2c99b080
subsection
6
13
Human network mapping.
Structural networks (connectomes) were mapped for each individual using a deterministic tractography pipeline from the MRtrix3 software (http://www.mrtrix.org/, ). Diffusion tensors were estimated from the preprocessed diffusion weighted images using a iteratively reweighted linear least squares estimator. White matter...
{ "cite_spans": [ { "arxiv_id": "", "doi": "10.1038/s41467-017-01285-x", "end": 164, "openalex_id": "https://openalex.org/W2766639217", "raw": "K. H. Maier-Hein, P. F. Neher, J.-C. Houde, M.-A. Côté, E. Garyfallidis, J. Zhong, M. Chamberland, F.-C. Yeh, Y.-C. Lin, Q. Ji, W. E. Reddic...
10.1073/pnas.1801351115
1801.07938
Navigation of brain networks
[ "Caio Seguin", "Martijn P. van den Heuvel", "Andrew Zalesky" ]
[ "q-bio.NC" ]
2,018
en
Quantitative Biology
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4ff99061efba8bf9d4e13373782a33306145ba88
subsection
7
13
Connectome thresholding.
Density-based thresholding of connection weights was applied to the group-averaged connectome in order to filter out potentially noisy and spurious connections . A density threshold of 15% consists of keeping the top 15% highest weighted connections and deleting the remaining ones. Since the true connection density of ...
{ "cite_spans": [ { "arxiv_id": "", "doi": "10.1016/j.neuroimage.2013.04.087", "end": 161, "openalex_id": "https://openalex.org/W2146406922", "raw": "A. Fornito, A. Zalesky, and M. Breakspear, “Graph analysis of the human connectome: promise, progress, and pitfalls,” Neuroimage, vol....
10.1073/pnas.1801351115
1801.07938
Navigation of brain networks
[ "Caio Seguin", "Martijn P. van den Heuvel", "Andrew Zalesky" ]
[ "q-bio.NC" ]
2,018
en
Quantitative Biology
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07f9726d55bc19086d4f9da098b21627ca84675d
subsection
8
13
Null network models.
Four null network models were used in this work: (M1) topologically randomized (rewired) networks, (M2) spatially randomized (repositioned) networks, (M3) progressively randomized networks and (M4) progressively clusterized networks. Null models (M1) and (M2) were employed in the sections Navigability of the human conn...
{ "cite_spans": [ { "arxiv_id": "", "doi": "10.1016/j.neuroimage.2009.10.003", "end": 679, "openalex_id": "https://openalex.org/W2167822639", "raw": "M. Rubinov and O. Sporns, “Complex network measures of brain connectivity: uses and interpretations,” Neuroimage, vol. 52, pp. 1059–69...
10.1073/pnas.1801351115
1801.07938
Navigation of brain networks
[ "Caio Seguin", "Martijn P. van den Heuvel", "Andrew Zalesky" ]
[ "q-bio.NC" ]
2,018
en
Quantitative Biology
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cd87e0c51f2643c66a2f6e47279bcaf4079d8e4f
subsection
9
13
Navigation centrality.
Binary and weighted betweenness centralities were computed using the Brain Connectivity Toolbox, representing the absolute number of shortest paths that pass through each node of the network. Similarly, the navigation centrality of node i defined as c(i) = \sum _{s \ne i \ne t} \pi _{st}(i), where \pi _{st}=1 if the su...
{ "cite_spans": [] }
10.1073/pnas.1801351115
1801.07938
Navigation of brain networks
[ "Caio Seguin", "Martijn P. van den Heuvel", "Andrew Zalesky" ]
[ "q-bio.NC" ]
2,018
en
Quantitative Biology
[ -0.037740349769592285, -0.03215709701180458, -0.05442909151315689, 0.03575722873210907, -0.01607854850590229, 0.007017203606665134, 0.03572671860456467, 0.0022710568737238646, 0.015071732923388481, 0.014575951732695103, -0.026482315734028816, -0.021021101623773575, 0.016017530113458633, 0....
3dbf8c035a66b5107bef97ead2cb7f7179791f09
subsection
10
13
Navigation and functional connectivity.
Our implementation of navigation identifies paths based on the Euclidean distance between network nodes. Thus, a natural definition of navigation path length is to consider the physical distance traversed from one node to another. For our FC analysis, we defined navigation path length from i to j as \Lambda ^{nav}_{ij}...
{ "cite_spans": [] }
10.1073/pnas.1801351115
1801.07938
Navigation of brain networks
[ "Caio Seguin", "Martijn P. van den Heuvel", "Andrew Zalesky" ]
[ "q-bio.NC" ]
2,018
en
Quantitative Biology
[ -0.0604446716606617, -0.05925469473004341, -0.057515501976013184, 0.023341834545135498, -0.012555771507322788, 0.0048743244260549545, -0.0066936141811311245, -0.04836184158921242, -0.002498186659067869, 0.024958981201052666, -0.006411376409232616, 0.004050494637340307, -0.022319676354527473,...
8572da1b444b256399028cfc49f1f60353bdc163
subsection
11
13
Distance scaling of connection weights.
A common practice in connectomics studies based on white matter tractography is to scale streamline counts by average fiber lengths . This is motivated by the notion that certain tractography algorithms are biased towards overestimating the streamline count of long fiber bundles. We chose not to perform distance-based ...
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10.1073/pnas.1801351115
1801.07938
Navigation of brain networks
[ "Caio Seguin", "Martijn P. van den Heuvel", "Andrew Zalesky" ]
[ "q-bio.NC" ]
2,018
en
Quantitative Biology
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6384cca74e1a93c0ee926a0718844900c53a7157
subsection
12
13
Distance scaling of connection weights.
(A) Whole brain correlations between FC and Euclidean distance (blue), weighted shortest paths (orange), binary shortest paths (yellow) and navigation distance (green). (B) Scatter plot between navigation distances and FC for all brain regions. Green line indicate the linear fit between the two measures. (C-D) Right he...
{ "cite_spans": [] }
10.1073/pnas.1801351115
1801.07938
Navigation of brain networks
[ "Caio Seguin", "Martijn P. van den Heuvel", "Andrew Zalesky" ]
[ "q-bio.NC" ]
2,018
en
Quantitative Biology
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42f183df939a3018a657de2b0922b949b7a98128
abstract
0
59
Abstract
We investigate the existence of weak expanding solutions of the harmonic map flow for maps with values into a smooth closed Riemannian manifold. We prove the existence of such solutions in case the target manifold is isometrically embedded as a hypersurface of some Euclidean space and the initial condition is a Lipschi...
{ "cite_spans": [] }
1801.08012
Existence of expanders of the harmonic map flow
[ "Alix Deruelle", "Tobias Lamm" ]
[ "math.DG" ]
2,018
en
Mathematics
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42ba5f0b6b8d15fa864bae3b634117c04ff8bfbe
subsection
1
59
Introduction
In this paper, we consider the Cauchy problem for the harmonic map flow of maps (u(t))_{t\ge 0} from \mathop {\rm \mathbb {R}}\nolimits ^n, n\ge 3 to a closed smooth Riemannian manifold (N,g) isometrically embedded in some Euclidean space \mathop {\rm \mathbb {R}}\nolimits ^m, m\ge 2. More precisely, we study the parab...
{ "cite_spans": [] }
1801.08012
Existence of expanders of the harmonic map flow
[ "Alix Deruelle", "Tobias Lamm" ]
[ "math.DG" ]
2,018
en
Mathematics
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c0ab49361102e298689beabc8d9fc4b1f56f030b
subsection
2
59
Introduction
Indeed, if u is an expanding solution in the previous sense then the map U(x):=u(x,1) for x\in \mathbb {R}^n, satisfies the elliptic system\left\lbrace \begin{aligned}&\Delta _f U+A(U)(\nabla U,\nabla U)=0,\quad \mbox{on $\mathbb {R}^n$},&\\ &\lim _{|x|\rightarrow +\infty }U(x)=u_0(x/|x|),& \end{aligned} \right.where, ...
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1801.08012
Existence of expanders of the harmonic map flow
[ "Alix Deruelle", "Tobias Lamm" ]
[ "math.DG" ]
2,018
en
Mathematics
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9e3e1b120b1197b32463b36392162eb2d777dd1a
subsection
3
59
Introduction
Our main result is the followingTheorem 1.1 Let n\ge 3 and m\ge 2 be two integers and let u_0:\mathbb {R}^n\rightarrow (N,g)\subset \mathop {\rm \mathbb {R}}\nolimits ^m be a Lipschitz 0-homogeneous map which is homotopic to a constant.Then there exists a weak expander u(\cdot ,1)=:U(\cdot ) of the harmonic map flow c...
{ "cite_spans": [ { "arxiv_id": "", "doi": "10.1007/bf01161997", "end": 1650, "openalex_id": "https://openalex.org/W2034075141", "raw": "Yun Mei Chen and Michael Struwe. Existence and partial regularity results for the heat flow for harmonic maps. Math. Z., 201(1):83–103, 1989.", ...
1801.08012
Existence of expanders of the harmonic map flow
[ "Alix Deruelle", "Tobias Lamm" ]
[ "math.DG" ]
2,018
en
Mathematics
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e132f75e8980f790b9ef7def661e35a774b345a3
subsection
4
59
Introduction
Since the initial condition u_0 is allowed to have large local-in-space energy, it is likely that uniqueness will fail. In particular, the authors do not know if the solution produced by Theorem REF coming out of a 0-homogeneous harmonic map will stay harmonic.Now a few words about the proof of Theorem REF . A direct p...
{ "cite_spans": [ { "arxiv_id": "", "doi": "10.1007/bf01161997", "end": 944, "openalex_id": "https://openalex.org/W2034075141", "raw": "Yun Mei Chen and Michael Struwe. Existence and partial regularity results for the heat flow for harmonic maps. Math. Z., 201(1):83–103, 1989.", ...
1801.08012
Existence of expanders of the harmonic map flow
[ "Alix Deruelle", "Tobias Lamm" ]
[ "math.DG" ]
2,018
en
Mathematics
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ee97c659476e4666de4cfb5d2bb3ca64b07a836c
subsection
5
59
Introduction
Then for any K>0, there exists a smooth Homogeneous Ginzburg-Landau expander u_K coming out of u_0:\left\lbrace \begin{aligned}&\Delta _fU_K+K(1-|U_K|^2)U_K=0,&\\ &\lim _{t\rightarrow 0^+}u_K(\cdot ,t)= u_0,\quad \mbox{in the weak sense.}& \end{aligned} \right.Moreover, ife_K(u_K)(t):=\frac{1}{2}\left(|\nabla u_K|^2+\f...
{ "cite_spans": [ { "arxiv_id": "", "doi": "10.1016/j.anihpc.2011.06.004", "end": 1453, "openalex_id": "https://openalex.org/W1997447267", "raw": "Pierre Germain and Melanie Rupflin. Selfsimilar expanders of the harmonic map flow. Ann. Inst. H. Poincaré Anal. Non Linéaire, 28(5):743–...
1801.08012
Existence of expanders of the harmonic map flow
[ "Alix Deruelle", "Tobias Lamm" ]
[ "math.DG" ]
2,018
en
Mathematics
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8b7598b43647a74a587c39d41b44220bdf4fccbf
subsection
6
59
Introduction
In this case, the homogeneity is of degree -1. To prove Theorem REF , we proceed similarly to their work by using the Leray-Schauder degree theory. For this, one needs a path of initial conditions (u_0^{\sigma })_{0\le \sigma \le 1)}:\mathbb {S}^{n-1}\rightarrow N connecting the restriction u_0^0 of u_0 to \mathbb {S}^...
{ "cite_spans": [ { "arxiv_id": "", "doi": "10.2422/2036-2145.201502_004", "end": 1202, "openalex_id": "https://openalex.org/W2964296827", "raw": "A. Deruelle. Asymptotic estimates and compactness of expanding gradient ricci solitons. Annali della Scuola Normale Superiore di Pisa, Vo...
1801.08012
Existence of expanders of the harmonic map flow
[ "Alix Deruelle", "Tobias Lamm" ]
[ "math.DG" ]
2,018
en
Mathematics
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aae1e45a35bf8e389ebb39e920cbc185bc6f532b
subsection
7
59
Deformation theory of expanders (with small energy)
From now on, let u:\mathbb {R}^n\rightarrow N be an expanding solution of the harmonic map flow, fixed once and for all. We consider the linearisation of equation (REF ) around u.
{ "cite_spans": [] }
1801.08012
Existence of expanders of the harmonic map flow
[ "Alix Deruelle", "Tobias Lamm" ]
[ "math.DG" ]
2,018
en
Mathematics
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4cd16dd7e7c13dcb578804b9f62a964a97c1a5e2
subsection
8
59
Deformation theory of expanders (with small energy)
It takes the following time-dependent form: if u+h is an expander then,\partial _t(u+h)&=&\Delta (u+h)+A(u+h)(\nabla (u+h),\nabla (u+h))|,is equivalent to\partial _th&=&\Delta h+ A(u+h)(\nabla (u+h),\nabla (u+h))-A(u)(\nabla u,\nabla u)\\ &=:&\Delta h+R(u,\nabla u,h,\nabla h),\\whereR(u,\nabla u,h,\nabla h)&:=&A(u+h)(\...
{ "cite_spans": [] }
1801.08012
Existence of expanders of the harmonic map flow
[ "Alix Deruelle", "Tobias Lamm" ]
[ "math.DG" ]
2,018
en
Mathematics
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40f859987f90813f2c37602917ec42338eaae9f2
subsection
9
59
Deformation theory of expanders (with small energy)
The number \sbox {\Vert }\mbox{[}0pt][l]{\usebox }\rule [0.5/2]{}{0.5pt}h\Vert ^p_{L^p(P(x,r))} is the normalized p-norm of h on the parabolic neighborhood P(x,r).Finally, as in , we introduce a somewhat intermediate function space Y:Y:=\left\lbrace R:\mathbb {R}^n\rightarrow \mathbb {R}^m\quad |\quad \sup _{t\in \ma...
{ "cite_spans": [ { "arxiv_id": "", "doi": "10.4310/ajm.2012.v16.n2.a3", "end": 1076, "openalex_id": "https://openalex.org/W2963479749", "raw": "Herbert Koch and Tobias Lamm. Geometric flows with rough initial data. Asian J. Math., 16(2):209–235, 2012.", "source_ref_id": "171be...
1801.08012
Existence of expanders of the harmonic map flow
[ "Alix Deruelle", "Tobias Lamm" ]
[ "math.DG" ]
2,018
en
Mathematics
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5526f918a8613d25dc2e55218822eaa218b6f98d
subsection
10
59
Deformation theory of expanders (with small energy)
Besides, uniqueness holds in a neighbourhood of u for the topology of X.The proof follows closely the one in the paper which in turn is motivated by the paper .First of all, let us fix some map v_0\in BMO(\mathbb {R}^n,N) and define the map T: X\rightarrow X as follows:T(h):=K_t\ast (v_0-u_0)+\int _0^tK_{t-s}\ast R(u,\...
{ "cite_spans": [ { "arxiv_id": "", "doi": "10.1007/s00205-010-0343-5", "end": 161, "openalex_id": "https://openalex.org/W2055891097", "raw": "Changyou Wang. Well-posedness for the heat flow of harmonic maps and the liquid crystal flow with rough initial data. Arch. Ration. Mech. Ana...
1801.08012
Existence of expanders of the harmonic map flow
[ "Alix Deruelle", "Tobias Lamm" ]
[ "math.DG" ]
2,018
en
Mathematics
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9f66803a2c92fb3ce0cbe34dab1ad5b6864066c3
subsection
11
59
Existence of smooth expanders with arbitrary energy
Let (N,g) be a closed Riemannian manifold which is isometrically embedded in some Euclidean space \mathop {\rm \mathbb {R}}\nolimits ^m. Then there exists a tubular neighbourhood T_{2\delta _N}(N) of N such that the projection map \Pi _N:T_{2\delta _N}(N)\rightarrow N is well-defined and smooth. As in , let \chi be a s...
{ "cite_spans": [ { "arxiv_id": "", "doi": "10.1007/bf01161997", "end": 460, "openalex_id": "https://openalex.org/W2034075141", "raw": "Yun Mei Chen and Michael Struwe. Existence and partial regularity results for the heat flow for harmonic maps. Math. Z., 201(1):83–103, 1989.", ...
1801.08012
Existence of expanders of the harmonic map flow
[ "Alix Deruelle", "Tobias Lamm" ]
[ "math.DG" ]
2,018
en
Mathematics
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5120898030eb343d030a4f6a6054ba8c4f08f106
subsection
12
59
Existence of smooth expanders with arbitrary energy
Then for any K>0, there exists a regular Chen-Struwe expanding solution u_K coming out of u_0\left\lbrace \begin{aligned}&-\Delta _fU_K+K\chi ^{\prime }\left( d^2_{N}(U_K)\right)\nabla \left( \frac{d^2_{N}}{2}\right)(U_K)=0,&\\ &\lim _{t\rightarrow 0^+}u_K(\cdot ,t)= u_0\quad \mbox{in the weak sense. } \end{aligned} \r...
{ "cite_spans": [ { "arxiv_id": "", "doi": "10.1007/s00222-013-0468-x", "end": 1508, "openalex_id": "https://openalex.org/W1966573859", "raw": "Hao Jia and Vladimír Šverák. Local-in-space estimates near initial time for weak solutions of the Navier-Stokes equations and forward self-s...
1801.08012
Existence of expanders of the harmonic map flow
[ "Alix Deruelle", "Tobias Lamm" ]
[ "math.DG" ]
2,018
en
Mathematics
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e6c00d114cd777f40f70b10d801a9863c406a28e
subsection
13
59
Existence of smooth expanders with arbitrary energy
Notice that the time-dependent map V_K(\cdot ,t):=V_K(\cdot /\sqrt{t}) will satisfy the bounds(\sqrt{t}+|x|)^{2}|V_K(x,t)|+(\sqrt{t}+|x|)^{3}|\nabla V_K(x,t)|\le Ct,\quad \forall x\in \mathop {\rm \mathbb {R}}\nolimits ^n,\quad \forall t>0,\quad k\in \lbrace 0,1\rbrace .Denote by U_0(t) the caloric extension of the map...
{ "cite_spans": [] }
1801.08012
Existence of expanders of the harmonic map flow
[ "Alix Deruelle", "Tobias Lamm" ]
[ "math.DG" ]
2,018
en
Mathematics
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3761b14bcfcd0d73999600d36ed9131ab6bfebdb
subsection
14
59
Existence of smooth expanders with arbitrary energy
Then the caloric extension U_0 of u_0 satisfies&&\Vert U_0\Vert _{L^{\infty }}\le \Vert u_0\Vert _{L^{\infty }}, \\ &&\sup _{x\in \mathop {\rm \mathbb {R}}\nolimits ^n}(1+|x|)|\nabla ^kU_0|(x)\le C(k,u_0),\quad \forall k\ge 1,\\ &&(1+|x|)d_N(U_0(x))\le (1+|x|)|U_0(x)-u_0(x/|x|)|\le C(u_0).Moreover, if u_0 is in C^3_{lo...
{ "cite_spans": [] }
1801.08012
Existence of expanders of the harmonic map flow
[ "Alix Deruelle", "Tobias Lamm" ]
[ "math.DG" ]
2,018
en
Mathematics
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b0b16c5d80f5d169972a7178d71a12b67ca50bfe
subsection
15
59
Existence of smooth expanders with arbitrary energy
In particular, this implies thatU_0(x)=u_0(x/|x|)+\textit {O}((1+|x|)^{-1}),as x tends to +\infty .Therefore, d_N(U_0(x))\le |U_0(x)-u_0(x/|x|)|=\textit {O}((1+|x|)^{-1}).Now, if u_0 is in C^3_{loc}(\mathop {\rm \mathbb {R}}\nolimits ^n\setminus \lbrace 0\rbrace ), the decay on the first and the second derivatives of U...
{ "cite_spans": [] }
1801.08012
Existence of expanders of the harmonic map flow
[ "Alix Deruelle", "Tobias Lamm" ]
[ "math.DG" ]
2,018
en
Mathematics
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e088e0fa0e3f7bb0385910f163c8052b027d7e3a
subsection
16
59
Existence of smooth expanders with arbitrary energy
If n=3, we consider a barycentric approximation of u_0 as follows: if \eta :\mathop {\rm \mathbb {R}}\nolimits ^n\rightarrow [0,1] denotes any smooth function such that \eta \equiv 1 if |x|\ge 2 and \eta \equiv 0 if |x|\le 1, we defineU_0^b:=(1-\eta )P+\eta u_0,where P\in N is fixed.The properties of U^b_0 can be summa...
{ "cite_spans": [] }
1801.08012
Existence of expanders of the harmonic map flow
[ "Alix Deruelle", "Tobias Lamm" ]
[ "math.DG" ]
2,018
en
Mathematics
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380bf8cf70e97baddda25352be1dca5cda37a200
subsection
17
59
Existence of smooth expanders with arbitrary energy
Note that this path is chosen inside the homotopy class of [u_0]\in \pi _{n-1}(N).Thus, solving (REF ) amounts to solving the static Chen-Struwe equation&&\Delta _fV_K-K\chi ^{\prime }\left( d^2_{N}(U_0^{\sigma }+V_K)\right)\nabla \left( \frac{d^2_N}{2}\right)(U_0^{\sigma }+V_K)=0,\quad V_K\in X.If V\in X, K>0 and \sig...
{ "cite_spans": [] }
1801.08012
Existence of expanders of the harmonic map flow
[ "Alix Deruelle", "Tobias Lamm" ]
[ "math.DG" ]
2,018
en
Mathematics
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df5d7eb12772aa63bb9ceb280e20344e91277dea
subsection
18
59
Body
In this section, we prove that the map F_K^{\sigma }:X\rightarrow X is compact and continuous.Note that the map F_K^{\sigma } can also be formally interpreted asF_K^{\sigma }(V)(x,t)=-K\int _0^t\int _{\mathop {\rm \mathbb {R}}\nolimits ^n}\mathcal {K}^{\sigma }_{t-s}(x,y)\frac{1}{s}\chi ^{\prime }(d^2_{N}(U_0^{\sigma }...
{ "cite_spans": [] }
1801.08012
Existence of expanders of the harmonic map flow
[ "Alix Deruelle", "Tobias Lamm" ]
[ "math.DG" ]
2,018
en
Mathematics
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110a0858885735507b019b9d0e9cf5a7e33a49e7
subsection
19
59
Body
To do so, given V\in X, we first solve the following Dirichlet problem&&\Delta _fW_R-K\chi ^{\prime }(d^2_{N}(U_0^{\sigma }))d_{U_0^{\sigma }}d_N(W_R)\nabla d_N(U_0^{\sigma })=Q(U_0^{\sigma },V),\quad \text{ on } B(0,R)\subset \mathop {\rm \mathbb {R}}\nolimits ^n,\\ &&W_R=0,\quad \text{ on } \partial B(0,R),\\ &&\text...
{ "cite_spans": [] }
1801.08012
Existence of expanders of the harmonic map flow
[ "Alix Deruelle", "Tobias Lamm" ]
[ "math.DG" ]
2,018
en
Mathematics
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2b8dde87eaa1f007adc480dd473bde1e6e6bf3a5
subsection
20
59
Body
Therefore,Q(U_0^{\sigma },V)=d_N(U_0^{\sigma })\nabla d_N(U_0^{\sigma })+d_N(U_0^{\sigma })\textit {O}(V)+V\ast V,where, if A and B are two tensors, A\ast B denotes any contraction of linear combinations of the tensor product A\otimes B. By using Lemma REF together with (REF ), one gets:\sup _{x\in \mathop {\rm \mathbb...
{ "cite_spans": [] }
1801.08012
Existence of expanders of the harmonic map flow
[ "Alix Deruelle", "Tobias Lamm" ]
[ "math.DG" ]
2,018
en
Mathematics
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944a8ab867966f98f9d79f9810fb02eca7d82642
subsection
21
59
Body
Now observe that the function f^{-1} is a good barrier function since\Delta _ff^{-1}&=&-f^{-2}\Delta _ff+2|\nabla f|^2f^{-3}\\ &=&-f^{-1}\left(1-2f^{-2}\frac{|x|^2}{4}\right)\\ &\le &-Cf^{-1},for some positive constant C. Indeed, one can check that for n\ge 2 we have\inf _{x\in \mathop {\rm \mathbb {R}}\nolimits ^n} \l...
{ "cite_spans": [] }
1801.08012
Existence of expanders of the harmonic map flow
[ "Alix Deruelle", "Tobias Lamm" ]
[ "math.DG" ]
2,018
en
Mathematics
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7edcc26ec6e07fddc6a6ac5de2a608600689ecfa
subsection
22
59
Body
This is the content of the next proposition.Proposition 3.8 The solution F_K^{\sigma }(V) satisfies the weighted a priori C^1 bound\sup _{\mathop {\rm \mathbb {R}}\nolimits ^n}f^{3/2}|\nabla F_K^{\sigma }(V)|\le C(n,m,K)\Vert Q(U_0^{\sigma },V)\Vert _{X}.Strictly speaking, the solution F_K^{\sigma }(V)=:F(V) is in C^{...
{ "cite_spans": [] }
1801.08012
Existence of expanders of the harmonic map flow
[ "Alix Deruelle", "Tobias Lamm" ]
[ "math.DG" ]
2,018
en
Mathematics
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2adb523fcdda76ee38119e47d9b37b2eb5d1e571
subsection
23
59
Body
Moreover, by interior parabolic Schauder estimates applied to the corresponding time-dependent solution F(V)(x,t):=F(V)(x/\sqrt{t}) defined on \mathop {\rm \mathbb {R}}\nolimits ^n\times \mathop {\rm \mathbb {R}}\nolimits _+, one gets the bounds\sup _{x\in \mathop {\rm \mathbb {R}}\nolimits ^n}f(x)\Vert F(V)\Vert _{C^{...
{ "cite_spans": [] }
1801.08012
Existence of expanders of the harmonic map flow
[ "Alix Deruelle", "Tobias Lamm" ]
[ "math.DG" ]
2,018
en
Mathematics
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9331f3d883f813a1b972957b35b11811e9a84024
subsection
24
59
Body
Now, as we know that the function f^{2}|\nabla F(V)|^2 is bounded, the function f^{2}|\nabla F(V)|^2-k^{-1}\ln f-Af^{-1} goes to -\infty as x goes to +\infty . Therefore, it attains its maximum. The maximum principle applied to the previous differential inequality impliesf^{2}|\nabla F(V)|^2-k^{-1}\ln f-Af^{-1}\le 2Ck^...
{ "cite_spans": [] }
1801.08012
Existence of expanders of the harmonic map flow
[ "Alix Deruelle", "Tobias Lamm" ]
[ "math.DG" ]
2,018
en
Mathematics
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9d4029684c91c73bc79d99e2e119b8a65c09adf2
subsection
25
59
Body
In particular, by Taylor's theorem,\sup _{\mathop {\rm \mathbb {R}}\nolimits ^n}f^{2+i/2}|\nabla ^i(Q(U_0,V)-Q(U_0,0))|\le C(K,n,m,\Vert V\Vert _{X}),\quad i=0,1.As in the proof of Proposition REF , one can use a barrier function of the form f^{-2} in order to prove that G(V) decays like f^{-2} uniformly with respect t...
{ "cite_spans": [] }
1801.08012
Existence of expanders of the harmonic map flow
[ "Alix Deruelle", "Tobias Lamm" ]
[ "math.DG" ]
2,018
en
Mathematics
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fb21c54fd964e6556640a033c98e06e070e581d1
subsection
26
59
Body
Moreover, this last fact also yields the desired estimate if the maximum is attained on the boundary.By interior parabolic Schauder estimates, one has the following corollary.Corollary 3.11 For any k\ge 0, there is a positive constant M(K,k) uniform in \sigma \in [0,1] and K>0 such that if V\in X is a fixed point of t...
{ "cite_spans": [] }
1801.08012
Existence of expanders of the harmonic map flow
[ "Alix Deruelle", "Tobias Lamm" ]
[ "math.DG" ]
2,018
en
Mathematics
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2a1d32bbfb139587b1707d64de6308e01f336553
subsection
27
59
Well-posedness of the homogeneous Chen-Struwe equation for small initial data
In this subsection, we assume that \sigma is close to 1 and hence U_0^\sigma is close to a constant map in the sense that\Vert U_0^{\sigma }-c\Vert _{L^\infty }+\sup _{x\in \mathop {\rm \mathbb {R}}\nolimits ^n}(1+|x|)|\nabla U_0^{\sigma }(x)|\le C(u_0^\sigma ),where c\in \mathbb {S}^{m-1} and where \lim _{\sigma \righ...
{ "cite_spans": [] }
1801.08012
Existence of expanders of the harmonic map flow
[ "Alix Deruelle", "Tobias Lamm" ]
[ "math.DG" ]
2,018
en
Mathematics
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2748f8b1c6fd62772326e6cc84b308fbf5213945
subsection
28
59
A Bochner formula
It is a straightforward adaptation from to get the following crucial Bochner formula:Proposition 3.13 (Bochner formula) Let u:\mathop {\rm \mathbb {R}}\nolimits ^n\times (0,T)\rightarrow \mathop {\rm \mathbb {R}}\nolimits ^m be a smooth solution to the Homogeneous Chen-Struwe flow:\partial _tu-\Delta u+\frac{K}{t}\chi...
{ "cite_spans": [ { "arxiv_id": "", "doi": "10.1007/bf01161997", "end": 400, "openalex_id": "https://openalex.org/W2034075141", "raw": "Yun Mei Chen and Michael Struwe. Existence and partial regularity results for the heat flow for harmonic maps. Math. Z., 201(1):83–103, 1989.", ...
1801.08012
Existence of expanders of the harmonic map flow
[ "Alix Deruelle", "Tobias Lamm" ]
[ "math.DG" ]
2,018
en
Mathematics
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bd3085df602f595d735b0b3008485ee465ef1ca8
subsection
29
59
A Bochner formula
If d_{N}(u)\le 2\cdot \delta _N, by using the fact that \chi ^{\prime } is nonnegative we obtain(\partial _t-\Delta )e_K(u)+|\nabla ^2u|^2+\frac{K^2}{t^2}\chi ^{\prime 2}d^2_{N}(u)&\le &\frac{1}{2t^2}K^2d^2_{N}(u)+c|\nabla u|^4,for some uniform positive constant c independent of K>0.Therefore, in all cases, this gives ...
{ "cite_spans": [] }
1801.08012
Existence of expanders of the harmonic map flow
[ "Alix Deruelle", "Tobias Lamm" ]
[ "math.DG" ]
2,018
en
Mathematics
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42a08b4684667bd7e1e4eecce40c43fe6b293a7f
subsection
30
59
An energy inequality and a monotonicity formula
We define the L^2_{loc} norm at scale R>0 of a map u:\mathop {\rm \mathbb {R}}\nolimits ^n\rightarrow \mathop {\rm \mathbb {R}}\nolimits ^m in H^1_{loc}(\mathop {\rm \mathbb {R}}\nolimits ^n,\mathop {\rm \mathbb {R}}\nolimits ^m) as follows:\Vert \nabla u\Vert ^2_{L^2_{loc,R}}:=\sup _{x_0\in \mathbb {R}^n}_{B(x_0,R)}|\...
{ "cite_spans": [] }
1801.08012
Existence of expanders of the harmonic map flow
[ "Alix Deruelle", "Tobias Lamm" ]
[ "math.DG" ]
2,018
en
Mathematics
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1b47b68b24ec296e30b8348f4aa7299409f83b4c
subsection
31
59
An energy inequality and a monotonicity formula
Then,E_{K,x_0}(u(t))&\le & \left(1+C\left(n,m,\Vert \nabla u_0\Vert _{L^2_{loc}},t\right)\right)\Vert \nabla u_0\Vert ^2_{L^2(B(x_0,1))},\quad \forall x_0\in \mathop {\rm \mathbb {R}}\nolimits ^n,\\ E_{K,loc}(u(t))&\le & \left(1+c_n \left(e^{c_nt}-1\right)\right)\Vert \nabla u_0\Vert _{L^2_{loc}}^2, \quad t>0,where \li...
{ "cite_spans": [] }
1801.08012
Existence of expanders of the harmonic map flow
[ "Alix Deruelle", "Tobias Lamm" ]
[ "math.DG" ]
2,018
en
Mathematics
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ffe34aefe91d3bcef9a3ab3dcbb1a6ba62176cfe
subsection
32
59
An energy inequality and a monotonicity formula
We multiply the Homogeneous Chen-Struwe flow equation by \phi _{x_0}^2\partial _tu where \phi _{x_0}:\mathbb {R}^n\rightarrow \mathbb {R}_+ is a smooth function with compact support in B(x_0,2) which equals 1 on B(x_0,1) and whose gradient is less than c, and then we integrate by parts to get\int _{\mathbb {R}^n}|\part...
{ "cite_spans": [] }
1801.08012
Existence of expanders of the harmonic map flow
[ "Alix Deruelle", "Tobias Lamm" ]
[ "math.DG" ]
2,018
en
Mathematics
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5f06a13494c4025e3bb97aabd9ebc43a6e50e01d
subsection
33
59
An energy inequality and a monotonicity formula
Therefore, by remark (REF ), one gets in particular:_{B(x_0,1)}|\nabla u(t)|^2dx\le \Vert \nabla u_0\Vert ^2_{L^2_{loc,1}}+c_n\int _0^t\Vert \nabla u(s)\Vert ^2_{L^2_{loc,1}}dt,which implies:\Vert \nabla u(t)\Vert ^2_{L^2_{loc}}\le \Vert \nabla u_0\Vert ^2_{L^2_{loc}}+c_n\int _0^t\Vert \nabla u(s)\Vert ^2_{L^2_{loc}}ds...
{ "cite_spans": [] }
1801.08012
Existence of expanders of the harmonic map flow
[ "Alix Deruelle", "Tobias Lamm" ]
[ "math.DG" ]
2,018
en
Mathematics
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790ce1b8779e0276a7b1863ef8f5ca9c555e47ca
subsection
34
59
An energy inequality and a monotonicity formula
We get\Vert (\nabla u(t))\chi _R\Vert _{L^2_{loc}}^2&\le & \Vert (\nabla u_0)\chi _R\Vert _{L^2_{loc}}^2+c_n\int _0^t\Vert (\nabla u(s))\chi _R\Vert _{L^2_{loc}}^2ds+\frac{c_n}{R^2}\int _0^t\Vert \nabla u(s)\Vert _{L^2_{loc}}^2ds\\ &\le &\Vert (\nabla u_0)\chi _R\Vert _{L^2_{loc}}^2+c_n\int _0^t\Vert (\nabla u(s))\chi ...
{ "cite_spans": [ { "arxiv_id": "", "doi": "10.1007/bf01161997", "end": 674, "openalex_id": "https://openalex.org/W2034075141", "raw": "Yun Mei Chen and Michael Struwe. Existence and partial regularity results for the heat flow for harmonic maps. Math. Z., 201(1):83–103, 1989.", ...
1801.08012
Existence of expanders of the harmonic map flow
[ "Alix Deruelle", "Tobias Lamm" ]
[ "math.DG" ]
2,018
en
Mathematics
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fd25dba86eca09901bf44ad509e3942ca9b3dfa0
subsection
35
59
An energy inequality and a monotonicity formula
We start with a Pohozaev identity like:Proposition 3.16 (Pohozaev identity) Let u:\mathop {\rm \mathbb {R}}\nolimits ^n\times (0,T)\rightarrow \mathop {\rm \mathbb {R}}\nolimits ^m be a smooth solution to the Homogeneous Chen-Struwe flow (with parameter K>0).
{ "cite_spans": [] }
1801.08012
Existence of expanders of the harmonic map flow
[ "Alix Deruelle", "Tobias Lamm" ]
[ "math.DG" ]
2,018
en
Mathematics
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