2012-11-26 07:01:15 8 Comments

I've been thinking about the following propagation of singularities result:

Let $X$ be a compact manifold, and let $P$ be a differential operator (of, say, order $m$) on $X$ whose principal symbol $\sigma_m(P)$ is real-valued. Suppose that $Pu=0$. Then the wavefront set of the solution $u$ is a union of maximally extended (null) bicharacteristics of $\sigma_m(P)$ in the co-sphere bundle $S^*X$.

Let's consider the Schrodinger operator on $X\times\mathbb{R}$:

$P=-i\partial_t+\Delta_x$.

My question is what, if anything, does the above propagation theorem tell us about solutions $u$ to the homogeneous Schrodinger equation?

### Related Questions

#### Sponsored Content

#### 0 Answered Questions

### Bilinear Strichartz estimates for the Schrodinger equation

**2019-07-10 17:33:50****Capublanca****36**View**0**Score**0**Answer- Tags: fa.functional-analysis ap.analysis-of-pdes

#### 2 Answered Questions

### [SOLVED] Finite speed of propagation of wave equation

**2014-06-18 23:06:57****student****1889**View**2**Score**2**Answer- Tags: ap.analysis-of-pdes

#### 0 Answered Questions

### Propagation of singularities and the Schrodinger equation

**2018-07-10 16:01:59****Thomas Young****72**View**1**Score**0**Answer- Tags: fa.functional-analysis real-analysis ap.analysis-of-pdes operator-theory micro-local-analysis

#### 3 Answered Questions

### [SOLVED] What does the flow of the principal symbol of the differential operator tell us about the PDE?

**2018-03-23 18:31:19****Saal Hardali****358**View**8**Score**3**Answer- Tags: ap.analysis-of-pdes ds.dynamical-systems sg.symplectic-geometry differential-operators linear-pde

#### 0 Answered Questions

### Propagation of Singularities

**2018-03-17 20:01:49****Victor Hugo****271**View**3**Score**0**Answer- Tags: ap.analysis-of-pdes differential-operators pseudo-differential-operators micro-local-analysis

#### 2 Answered Questions

### [SOLVED] Principal symbol for non-linear differential operators

**2017-09-18 06:54:59****Peter Wildemann****236**View**2**Score**2**Answer- Tags: ap.analysis-of-pdes elliptic-pde hyperbolic-pde

#### 2 Answered Questions

### [SOLVED] Symbol of the Laplace-Beltrami on $\mathbb{S}^2$

**2017-07-04 19:31:01****BaoLing****344**View**3**Score**2**Answer- Tags: fa.functional-analysis ap.analysis-of-pdes real-analysis differential-equations differential-operators

#### 0 Answered Questions

### 1D inhomogeneous linear Schrodinger equation

**2016-04-15 21:07:43****Sriram Nagaraj****69**View**2**Score**0**Answer- Tags: fa.functional-analysis ca.classical-analysis-and-odes ap.analysis-of-pdes differential-equations quantum-mechanics

#### 4 Answered Questions

### [SOLVED] Classification of PDE

**2011-06-04 20:00:13****AFK****3212**View**27**Score**4**Answer- Tags: ag.algebraic-geometry ap.analysis-of-pdes linear-pde d-modules

#### 3 Answered Questions

### [SOLVED] PDEs, boundary conditions, and unique solvability

**2010-06-24 23:00:27****Igor Khavkine****2737**View**12**Score**3**Answer- Tags: ap.analysis-of-pdes mp.mathematical-physics differential-equations

## 1 comments

## @Rafe Mazzeo 2012-11-26 15:21:29

There are propagation of singularities results for the Schr\"odinger operator, but they are usually stated on asymptotically Euclidean manifolds. Early results appear in a paper in CMP by Zelditch in around 82 or 83 exhibit the typical weird behaviour where singularities disappear then reappear at later discrete points of time. A more general `true' propagation theorem was proved by Craig, Kappeler and Strauss, but a much sharper set of results was eventually proved by Jared Wunsch, see his papers from the late '90's. I am not sure what the best results are on compact manifolds at this point, though there are some. For the sphere one can see the same phenomenon of solutions being singular at time 0 and then becoming smooth then instantaneously singular again at time $2\pi$, $4\pi$, and so on.

## @Terry Tao 2012-11-26 17:25:09

It's worth noting that due to infinite speed of propagation of the Schrodinger equation, singularities do not propogate as a flow on the traditional cosphere bundle (associated to states with a specific position and momentum), but on an extended phase space which mostly consists of states at spatial infinity, which in physical space exhibits quadratic phase type behaviour. So the classical Hormander-type theory doesn't apply directly, but variants of that theory do.