Pulsar Scattering, Lensing and Gravity Waves

Introduction
Convergent Plasma Lenses
Gravity Waves
Black Holes/Fuzzballs
Summary

Ue-Li Pen, Lindsay King, Latham Boyle
CITA

Feb 15, 2012

U. Pen

Introduction

Gravity Waves
Summary

Overview

IIII

Pulsar Scattering VLBI ISM holography, distance measures Enhanced Pulsar Timing Array gravity waves fuzzballs

U. Pen

Introduction

Gravity Waves
Summary

Pulsar Scattering

IIII

Pulsars scintillate strongly due to ISM propagation Lens of geometric size ∼ AU Can be imaged with VLBI (Brisken et al 2010) Deconvolved by interstellar holography (Walker et al 2008)

U. Pen

Introduction

Gravity Waves
Summary

Scattering Image

Data from Brisken et al, Holographic VLBI.

U. Pen

Introduction

Gravity Waves
Summary

ISM enigma

Scattering angle observed mas, 10⁻⁸rad.

IIII

Snell’s law: sin(θ₁)/ sin(θ₂) = n₂/n₁

n − 1 ∼ 10⁻¹²

.
4 orders of magnitude mismatch.

U. Pen

Introduction

Gravity Waves
Summary

Possibilities

II

turbulent ISM: sum of many small scatters. Cannot explain discrete images.

conﬁnement problem: super mini dark matter halos, cosmic strings?

III

Geometric alignment: Goldreich and Shridhar (2006) Snell’s law at grazing incidence: ∆α = (1 − n₂/n₁)/α grazing incidence is geometry preferred at 2-D structures

U. Pen

Introduction

Gravity Waves
Summary

Current Sheets

IIIII

generic outcome of reconnection Pang et al 2010 highly uncertain size, time scale Petschek vs Sweet-Parker long standing controversies

U. Pen

Introduction

Gravity Waves

Lenses

Summary

Gaussian Lens

III

Romani et al 1987, Clegg et al 1998 General highly triaxial system projected into highly elliptical pattern

U. Pen

Introduction

Gravity Waves

Lenses

Summary

Geometry

D_dsD_s

~

β = θ −

αˆ(D_dθ) = θ − α~(θ) ψ(θ) = σ_θ²κ₀exp(−θ²/2σ_θ²)

U. Pen

Introduction

Gravity Waves

Lenses

Summary

Plasma lensing

q

c_ph= c/ (1 − ω_p²/ω²)

q

ω_p

=

n_ee²/ꢀ₀m_e

Φ ≈ ω_p²c²/4ω²

critical points and caustics in large convergence limit:

ꢀ

√ ꢁ

e

κ₀

√

θ_c= ± 1 +

,

β_c= ±

2κ₀

e

magniﬁcations:

−1

1

µ =

,

1 + κ₀2 log(−κ₀) − 1

U. Pen

Introduction

Gravity Waves

Lenses

Summary

Time light curves

U. Pen

Introduction

Gravity Waves

Lenses

Summary

Time light curves

U. Pen

Introduction

Gravity Waves

Lenses

Summary

Fiedler Event

2.7 and 8.1 GHz light curves of QSO 0954+658 (Fiedler et al. 1994)

U. Pen

Introduction

Gravity Waves

Lenses

Summary

Holographic Secondary Spectrum

U. Pen

Introduction

Gravity Waves

Lenses

Summary

Pre/post-dictions

II

plasma underdensity in current sheets (not generic?) weak (logarithmic) frequency dependence of ESE (Fiedler et al 1987)

II

unresolved ESE VLBI image increase during ﬂux decrement (Lazio et al 2000)

pulsar inverse parabolic arc cross sections

U. Pen

Introduction

Gravity Waves

Lenses

Summary

Lensing applications

IIIII

Use ISM lens as a giant AU scale interferometer! straightforward to resolve the pulsar beam reﬂex motion. measure pulsar spin axis parallactic angle may be able to resolve pulsar emission region precise pulsar distance measurements

U. Pen

Introduction

Gravity Waves

Summary

Pulsar Gravity Wave Observatory

II

Major resolution and sensitivity boost compared to PTA Boyle and Pen 2010: resolution is λ/L, where λ ∼ 10ly and L ∼ 10kly, typically arc minute localization of sources

I

No longer in source confused limit, able to use pulsar intrinsic GW term

II

distances needed, from the lens distance reconstruction! during ESE, uses two screens to solve all unknowns.

U. Pen

Introduction
Gravity Waves

Summary

Black Holes Tests

I

Lai and Raﬁkov BH reconstruction: not possible to measure spin.

IIII

neglects coherent interference between images time delay measured to ∼ ns instead of ∼ms. 10,000 σ spin detection instead of < 1. what are we really testing? Einstein? no alternatives in strong ﬁeld?

U. Pen

Introduction
Gravity Waves

Summary

Fuzzballs

IIII

proposed by S. Mathur as alternatives to Black Holes has substantial cult following in stringy community resolves Hawking’s information paradox plausible argument due to failure of no-hair “theorem”

U. Pen

Introduction
Gravity Waves

Summary

Hair?

I

classical no-hair: decay of perturbations on dynamical time (ms)

II

Thermal hair: Boltzman factor supression?

70

exp(−∆E/kT) ∼ exp(−Mc²/kT) ∼ 10⁻¹⁰: macroscopic excitation most unlikely thing ever considered? (including boltzman brains!)

U. Pen

Introduction
Gravity Waves

Summary

Correction Factors

I

thermodynamic partition function weights by degeneracy of states: (n₁/n₂) exp(−(E₁− E₂)/kT).

IIII

entropy S = log n, proportionate to area cancels the Boltzman factor! round black holes have the least area – least likely state! generic black hole should be fractal, i.e. fuzzball

U. Pen

Introduction
Gravity Waves

Summary

Quantum Gravity

I

Stringy interpretation: quantum mechanics is unitary, fuzzball violate Hawking calculation premise

II

order unity deviations near schwarzschild radius deviations fall oﬀ as (r_s/r)^l: unlikely to be tested with accretion ﬂows at ꢀ 2M

II

pulsar-BH binary lensing: results in modiﬁed or absent fringes!

U. Pen

Introduction
Gravity Waves