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## Black Holes: The Information Paradox

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**Black Holes:The Information Paradox**Andrew Buccilli PH2010 Sophomore Seminar October 26, 2007**What is a Black Hole?**• Region of extremely dense packed matter • Gravity so strong that nothing can escape it • Gravitation balances EM radiation**Sizes**1. Supermassive Black Holes • millions to billions of times the mass of our sun • believed that most galaxies contain one at their galactic center • the slow acceleration of matter is one way of formation**2. Intermediate-Mass Black Hole**• mass is significantly more than SBH yet far less than SMBH • less evidence for existence • not clear how they form • too massive • lack extreme environment conditions 3. Stellar Black Hole • at least 1.5 solar masses • largest is 17.5 solar masses • formed by gravitational collapse of massive star**4. Quantum Mechanical Black Hole**• BH could exists at any mass in theory • lower mass, higher density of matter • Smallest mass is the plank mass • ~2 × 10^−8 kg • less mass: inconsistent and incomplete • BH mass < few times solar mass • no know processes to produce • Brian Greene (PhD. at Oxford University) • electron might be a micro black hole • mass, charge, spin • Note:Primordial black hole • extreme density of matter**Black Holes Have No Hair**• Complicated formation- Simple stationary state • Can be characterized by: • Mass • Angular momentum • Electric charge • Same properties • Unknown how formed • i.e. matter or antimatter**Event horizon**• Boundary of the region of escape • WARNING: “point of no return” • Not a solid surface • does not obstruct or slow down matter Singularity • Point where mass is entirely compressed • zero Volume • infinite gravitational pull and density • General relativity breaks down**Vacation Through a Black Hole**• Traveling through [T] - Outside observer [O] • [T] approaches “c” approaching BH • [T] experiences nothing abnormal through horizon • [O] sees [T] acting in a bizarre way • Spaghettification • Newton’s law of gravitation explains principles • [T] appears to slow down • [T] is spaghettified • [O] never sees anything inside the horizon • [T] appears flattened and frozen at horizon • [T] sees nothing unusual until reaching the singularity • All components of [T] are torn before striking • At the singularity- ?????????**Hawking Radiation**• Black holes slowly radiate away energy • Increases as mass decreases • Not actually black • Particle- antiparticle pair • both pulled in • both escape • one pulled in one escapes • BH lost minute amount of mass • radiation comes from the horizon**The Beautiful Equation**• Thermodynamics • Gravity • Quantum Physics • Relativity • Eventually a BH will radiate away all of its mass • Only thermal energy would remain • There is trouble on the horizon…**The Information Paradox**• Physics doesn’t work?! • Conservation of energy • Reversibility • Information cannot be destroyed**Black Hole Complementarity**• Opposing point • Info. never reached the horizon • Vaporized and radiated • Vacation revisited • Person falling in would be dead and alive? • Both points are true • String Theory • Agrees with both observers**Our Memories Are Safe?**• Parallel universes • Quantum gravity