Next Frontier

# Current Theory of the Universe

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              <h2>Standard Model</h2>
              
              <img src="img/SM_2.png" width="100%"><br>
              <font size="3"> Daniel Dominguez/CERN</font>
            </div>
            <br><br>
            <div style="text-align: left" class="fragment" data-fragment-index="2">
              <h3>   • Quantum theory of particles and fields</h3>
              <h3>   • Describes universe on the tiniest scales</h3>
            </div>
          </div>

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            <div class="fragment" data-fragment-index="3">
              <h2>General Relativity</h2>
              <img src="img/GR_2.png" width="85%"><br>
              <font size="2"> Kristina Armitage/Quanta Magazine</font>
            </div>
            <br><br><br><br>
            <div style="text-align: left" class="fragment" data-fragment-index="4">
              <h3>   • Einstein's theory of space-time and gravity</h3>
              <h3>   • Describes universe on the largest scales</h3>
            </div>
          </div>

# Extraordinarily Successful theories

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              <img src="img/cernmug.jpg" width="80%"><br>
              <font size="4"> * Bonus points for spotting mistake in the mug!</font>
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            <br><br>
            <div class="fragment" data-fragment-index="3">
              <img src="img/GR_mug.png" width="80%"><br>
            </div>

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            <div style="text-align: left" class="fragment" data-fragment-index="1">
              <h2>Standard Model</h2>
              <h3>   • Theory agree extremely well with experiment</h3>
              <h3>   • Predicted new particles and interactions</h3>
            </div>
            <div class="fragment fade-right" data-fragment-index="2">
              <h3>   • Higgs boson: discovered by CERN ~50 years after prediction</h3>

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            <br><br><br><br><br>
            <div style="text-align: left" class="fragment" data-fragment-index="3">
              <h2>General Relativity</h2>
              <h3>   • Tested from lab to extra-galactic scales</h3>
              <h3>   • Explained precession of mercury and gravitational lensing</h3>
              <div class="fragment fade-right" data-fragment-index="4">
                <h3>   • Gravitational waves: observed by LIGO ~100 years after prediction</h3>
                <h4>     • Coming up next: Cullan's talk</h4>
              </div>
            </div>

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            <br>
            <div class="fragment fade-right" data-fragment-index="5">
              <h2> However, all is not well...</h2>
            </div>

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# Unexplained Mysteries

<h2>Why is there so much more matter than anti-matter?</h2>
              <h3> • There should have been equal amounts created </h3>
            </div>

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<h2>Is there a quantum theory of gravitation?</h2>
              <h3> • Quantum mechanics and general relativity incompatible
              </h3>

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<h2>What is Dark Energy?</h2>
              <h3> • Explain accelerating expansion of the Universe </h3>

</div>

<h2>What is Dark Matter?</h2>
              <h3> • Missing mass from the universe </h3>
              <h3> • Matter that interacts <em>only</em> gravitationally? </h3>

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            <div class="fragment" data-fragment-index="3" style="text-align: left;" data-markdown>
              <h3> 95% of universe is "dark"; we can only use the 5% to learn about the rest! </h3>
            </div>

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# First Evidence for Dark Matter

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            <br>
            <h3>Coma Cluster</h3>
            <br>
            <img src="img/coma.jpg" width="75%"><br>
            <font size="3"> Sloan Digital Sky Survey + Spitzer Space
              Telescope
              [NASA / JPL-Caltech / L. Jenkins]</font>
            <br><br>
            <div style="text-align: left" class="fragment" data-fragment-index="2">
              <h3> • Clusters of galaxies observed to be too fast</h3>
              <h3> • Visible matter: not enough gravity to explain</h3>
              <h3> • <em>Dark matter</em>: interacts only gravitationally</h3>
            </div>
          </div>

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            <div class="fragment" data-fragment-index="3">
              <br>
              <h3>Major breakthrough</h3>
              <img src="img/vera-rubin.jpg" width="85%"><br>
              <font size="3">
                [AIP Emilio Segrè Visual Archives, Rubin Collection]
              </font>
            </div>
            <br>
            <div style="text-align: left" class="fragment" data-fragment-index="3">
              <h3> • Vera Rubin, Kent Ford, and others in the 1970s</h3>
              <h3 class="fragment"> • Dark Matter was <i><b>everywhere</b></i></h3>
              <h3 class="fragment"> • And there was <i><b>lots</b></i> of it</h3>
            </div>
          </div>

# Evidence builds up

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            <div>
              <h2> Rotation curves</h2>
              <h3> • Missing galactic matter</h3>
            </div>

<div class="fragment">
              <br>
              <h2> Gravitational lensing</h2>
              <h3> • Gravitational bending of light</h3>
            </div>

<div class="fragment">
              <br>
              <h2> Cosmic Microwave Background</h2>
              <h3> • Gravitational imprint on background radiation</h3>
            </div>

<div class="fragment">
              <br>
              <h2> Baryon Acoustic Oscillations</h2>
              <h3> • Sound waves (density fluctuations) in matter</h3>
              
            </div>

<div class="fragment">
              <br>
              <h2> Large-Scale Structure Simulations</h2>
              <h3> • Dark Matter required to match observations</h3>
            </div>
          </div>

<div style="text-align: center; float: right; width: 50%">
            <br><br>
            <b>Large-Scale Structure simulation:</b><br><br>
            <img src="img/Cosmic_web.jpg" width="90%"><br>
            <font size="3">[Volker Springel/MPI, Wikimedia Commons]</font>
          </div>

# How to break physics?

## Want to find direct evidence for physics _beyond_ standard model

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            <br>
            <div class="fragment">
              <h2> Particle Accelerators</h2>
              <h3> • Directly search for new particles</h3>
              <h3> • High energy, very expensive</h3>
            </div>

<div class="fragment">
              <br>
              <h2> CERN/LHC</h2>
              <h3> • Hoped to find evidence for something beyond</h3>
              <h3> • So far, no luck!</h3>
            </div>

<div class="fragment">
              <br>
              <h2> Alternative approach</h2>
              <h3> • Low-energy, high precision</h3>
              <h3> • Look for any violations of laws of physics</h3>
            </div>

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# Atomic Clocks:

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### Clock: frequency reference + count oscillations

<div class="fragment fade-in" data-fragment-index="0" style="text-align: center; float: left; width: 32%">
            <img src="img/Bohr.png" width="70%"><br>
            <font size="3"> [JabberWok/Wikimedia Commons]</font>
            <br><br>
            <h3>
              Atomic transition: "perfect*" frequency reference
            </h3>
          </div>

<div class="fragment fade-in" data-fragment-index="1" style="text-align: center; float: left; width: 32%">
            <img src="img/laser-JILA.jpg" width="100%">
            <font size="3"> [JILA]</font>
            <br><br><br><br>
            <h3>
              Laser: oscillations of light<br>
              Compare frequency to atomic transition
            </h3>
          </div>

<div class="fragment fade-in" data-fragment-index="2" style="text-align: center; float: right; width: 32%">
            <img src="img/Wcislo2016.png" width="95%">
            <font size="3"> [Wcislo, Science 2016]</font>
            <br><br>
            <h3>
              Lock on: Adjust laser to maximise transition rate
            </h3>
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# "Listen" to the hum of the universe using atomic clocks

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            <br> <br>
            <img src="img/NHanacek_NIST.png" width="90%"><br>
            <font size="3">[N Hanacek/NIST]</font>
          </div>

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            <br>
            <div class="fragment">
              <h2>Absurdly accurate</h2>
              <h3>  • Best atomic clocks: accurate to partis in 10<sup>18</sup> </h3>
              <h3>  • Lose less than 1 second over lifetime of the universe </h3>
            </div>
            <br>
            <br>
            <div class="fragment">
              <h2>Why?</h2>
              <h3>  • GPS navigation relies on high-accuracy clocks</h3>
              <h3>  • Geodesy and earth science</h3>
            </div>
            <br>
            <br>
            <div class="fragment">
              <h2>Also: fundamental science</h2>
              <h3>  • New physics: impact ticking of atomic clocks</h3>
              <h3>  • Clocks might tick differently in parts of the universe </h3>
            </div>
            <br>

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# Example experiment: GPS.DM

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            <br>
            <h3>• 30 Cs, Rb atomic clocks</h3>
            <h3>• Over 20 years of high-quality data</h3>
            <h3>• Publicly available (JPL)</h3>
            <h3>• 50,000 km Dark Matter observatory</h3>
            <br>
            <div class="fragment fade-in" data-fragment-index="1">
              <video width="75%" data-autoplay muted>
                <source src="img/GPSDM.mp4">
              </video><br>
              <font size="3">[Video: Conner Dailey (honors student)]</font>
            </div>
          </div>

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            <br>
            <br>  
            <img src="img/UNR.PNG" width="10%">  
            <img src="img/PI.png" width="10%">  
            <img src="img/GPSDM-logo.png" width="10%"><br>
            <img src="img/gps-data.png" width="45%">
            <br>
            <br>
            <div class="fragment fade-in" data-fragment-index="1">
              <h2>Look for "clumps" of dark matter</h2>
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            <br>
            <div class="fragment fade-in">
              
              <h3>• Didn't find any definitive evidence</h3>
              <h3>• Puts constraints on dark matter models</h3>
              <br>
              <b>Roberts</b>, Blewitt, Dailey, Murphy, Pospelov, Rollings,
              Sherman, Williams, Derevianko, <br>
              <a href="http://www.nature.com/articles/s41467-017-01440-4">
                [Nature Comms. (2017)]</a>

</div>

# Do the laws of nature break in extreme environments?
          ## Super-massive black hole at the Galactic Centre

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            <div class="fragment" data-fragment-index="1">
              
              <img src="img/Galactic_centre_pillars.jpg" width="100%"><br>
              <font size="3">[ESA / C. Carreau]</font>
            </div>
            <br>
            <div style="text-align: left" class="fragment" data-fragment-index="2">
              <h3>   • Use nature's atomic clocks:</h3>
              <h3>   • Atom's in stars near the black hole!</h3>
              <h3>   • Absorb/emit light at specific frequencies</h3>
              <h4>      • Compare to same atoms on Earth</h4>
              <br>
            </div>
            <div class="fragment" data-fragment-index="3">
              Hees, Do, <b>Roberts</b>, Ghez et al.,<a href="https://link.aps.org/doi/10.1103/PhysRevLett.124.081101">
                [Phys.Rev.Lett. (2020)]</a>
            </div>
          </div>

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            <div class="fragment" data-fragment-index="3">
              
              <img src="img/keck-ao.jpg" width="90%"><br>
            </div>
            <br>
            <div style="text-align: left" class="fragment" data-fragment-index="3">
              <h3>   • Keck telescope in Hawaii</h3>
              <h3>   • with UCLA Galactic Centre Group</h3>
              <br>
              <h4>    • Observations led by Tuan Do</h4>
              <h4>    • Andrea Ghez: 2020 Nobel prize for discovery of black hole</h4>
              <br>
            </div>
            <h4 class="fragment" data-fragment-index="4">    • More on black holes: Hugh's talk</h4>
          </div>

# The next frontier in fundamental physics

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            <br>
            <h2>Standard Model + General Relativity</h2>
            <h3>   • Extremely successful, but incomplete</h3>
            <h3>   • Our job to search for what's beyond</h3>

<br>
            <h2>Dark Matter</h2>
            <h3>   • Overwhelming evidence: completely in the dark</h3>
            <h3>   • Promising probe for physics beyond Standard Model</h3>

<br>
            <h2>Atomic Physics</h2>
            <h3>   • Low-energy, high precision alternative to CERN/LHC </h3>
            <h3>   • The next frontier in fundamental physics </h3>

<br><br><br><br><br>
            <h4> Benjamin M. Roberts (<a href="https://broberts.io">www.broberts.io</a>)</h4>

<h4> <i>Pint of Science, Brisbane, 15 May 2024</i></h4>
          </div>

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