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phd-thesis-beamer/thesis.tex
2020-11-06 14:35:41 +01:00

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\documentclass[10pt, aspectratio=169]{beamer}
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\usepackage{mathrsfs}
\usepackage{dsfont}
\usepackage{upgreek}
\usepackage{physics}
\usepackage{tensor}
\usepackage{graphicx}
\usepackage{transparent}
\usepackage{tikz}
\usepackage{import}
\usepackage{booktabs}
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\author[Finotello]{Riccardo Finotello}
\title[D-branes and Deep Learning]{D-branes and Deep Learning}
\subtitle{Theoretical and Computational Aspects in String Theory}
\institute[UniTO]{%
Scuola di Dottorato in Fisica e Astrofisica
\\[0.5em]
Università degli Studi di Torino
\\
and
\\
I.N.F.N.\ -- sezione di Torino
}
\date{15th December 2020}
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\begin{block}{#1}
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}{%
\end{block}
}
\newcommand{\highlight}[1]{\fcolorbox{yellow}{yellow!20}{#1}}
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% \AtBeginSection[]
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}
\section[CFT]{Conformal Symmetry and Geometry of the Worldsheet}
\subsection[Preliminary]{Preliminary Concepts and Tools}
\begin{frame}{Action Principle and Conformal Symmetry}
\begin{equationblock}{Polyakov's Action}
\begin{equation*}
S_P\qty[ \upgamma,\, X,\, \uppsi ]
=
-\frac{1}{4\pi}
\int\limits_{-\infty}^{+\infty} \dd{\uptau}
\int\limits_0^{\ell} \dd{\upsigma}
\sqrt{-\det \upgamma}\,
\upgamma^{\upalpha \upbeta}\,
\qty(%
\frac{2}{\upalpha'}\,
\partial_{\upalpha} X^{\upmu}\,
\partial_{\upbeta} X^{\upnu}
+
\uppsi^{\upmu}\,
\uprho_{\upalpha}
\partial_{\upbeta}
\uppsi^{\upnu}
)\,
\upeta_{\upmu\upnu}
\end{equation*}
\end{equationblock}
\pause
\begin{columns}
\begin{column}[t]{0.5\linewidth}
\highlight{Symmetries:}
\begin{itemize}
\item \textbf{Poincaré transf.}\ $X'^{\upmu} = \tensor{\Uplambda}{^{\upmu}_{\upnu}} X^{\upnu} + c^{\upmu}$
\item \textbf{2D diff.}\ $\upgamma'_{\upalpha \upbeta} = \tensor{\qty( \mathrm{J}^{-1} )}{_{\upalpha \upbeta}^{\uplambda \uprho}}\, \gamma_{\uplambda \uprho}$
\item \textbf{Weyl transf.}\ $\upgamma'_{\upalpha \upbeta} = e^{2 \upomega}\, \gamma_{\upalpha \upbeta}$
\end{itemize}
\end{column}
\pause
\begin{column}[t]{0.5\linewidth}
\highlight{Conformal symmetry:}
\begin{itemize}
\item \textbf{vanishing} stress-energy tensor: $\mathcal{T}_{\upalpha \upbeta} = 0$
\item \textbf{traceless} stress-energy tensor: $\trace{\mathcal{T}} = 0$
\item \textbf{conformal gauge} $\upgamma_{\upalpha \upbeta} = e^{\upphi}\, \upeta_{\upalpha \upbeta}$
\end{itemize}
\end{column}
\end{columns}
\end{frame}
\begin{frame}{Action Principle and Conformal Symmetry}
\begin{columns}
\begin{column}{0.6\linewidth}
\highlight{%
Let $z = e^{\uptau_E + i \upsigma} \Rightarrow \overline{\partial} \mathcal{T}( z ) = \partial \overline{\mathcal{T}}( \overline{z} ) = 0$:
}
\begin{equation*}
\mathcal{T}( z )\, \Upphi_h( w )
\stackrel{z \to w}{\sim}
\frac{h}{(z - w)^2} \Upphi_h( w )
+
\frac{1}{z - w} \partial_w \Upphi_h( w )
\end{equation*}
\begin{equation*}
\mathcal{T}( z )\, \mathcal{T}( w )
\stackrel{z \to w}{\sim}
\frac{\frac{c}{2}}{(z - w)^4}
+
\order{(z - w)^{-2}}
\end{equation*}
\begin{equationblock}{Virasoro algebra $\mathscr{V} \oplus \overline{\mathscr{V}}$}
\begin{eqnarray*}
\qty[ \overset{\scriptscriptstyle(-)}{L}_n,\, \overset{\scriptscriptstyle(-)}{L}_m ]
& = &
(n - m) \overset{\scriptscriptstyle(-)}{L}_{n + m} + \frac{c}{12} n \qty(n^2 - 1) \updelta_{n + m,\, 0}
\\
\qty[ L_n,\, \overline{L}_m ]
& = &
0
\end{eqnarray*}
\end{equationblock}
\end{column}
\begin{column}{0.4\linewidth}
\begin{figure}[h]
\centering
\resizebox{0.9\columnwidth}{!}{\import{img}{complex_plane.pgf}}
\end{figure}
\end{column}
\end{columns}
\end{frame}
\begin{frame}{Action Principle and Conformal Symmetry}
\highlight{Superstrings in $D$ dimensions:}
\begin{equation*}
\mathcal{T}( z )
=
-\frac{1}{\upalpha'}
\partial X( z ) \cdot \partial X( z )
-\frac{1}{2}
\uppsi( z ) \cdot \partial \uppsi( z )
\quad
\Rightarrow
\quad
c = \frac{3}{2} D
\end{equation*}
\pause
\begin{block}{$\qty( \uplambda, 0 )~/~\qty( 1 - \uplambda, 0 )$ Ghost System}
Introduce anti-commuting $\qty( b,\, c )$ and commuting $\qty( \upbeta,\, \upgamma )$ conformal fields:
\begin{equation*}
S_{\text{ghost}}\qty[ b,\, c,\, \upbeta,\, \upgamma ]
=
\frac{1}{2\uppi}
\iint \dd{z} \dd{\overline{z}}
\qty(%
b( z )\, \overline{\partial} c( z )
+
\upbeta( z )\, \overline{\partial} \upgamma( z )
)
\end{equation*}
where $\uplambda_b = 2$ and $\uplambda_c = -1$, and $\uplambda_{\upbeta} = \frac{3}{2}$ and $\uplambda_{\upgamma} = -\frac{1}{2}$.
\end{block}
\pause
\highlight{Consequence:}
\begin{equation*}
c_{\text{full}} = c + c_{\text{ghost}} = 0
\quad
\Leftrightarrow
\quad
D = 10.
\end{equation*}
\end{frame}
\begin{frame}{Extra Dimensions and Compactification}
\begin{block}{Compactification}
\begin{columns}
\begin{column}{0.7\linewidth}
\begin{equation*}
\mathscr{M}^{1,\, 9}
=
\mathscr{M}^{1,\, 3} \otimes \mathscr{X}_6
\end{equation*}
\begin{itemize}
\item $\mathscr{X}_6$ is a \textbf{compact} manifold
\item $N = 1$ \textbf{supersymmetry} is preserved in 4D
\item algebra of $\mathrm{SU}(3) \otimes \mathrm{SU}(2) \otimes \mathrm{U}(1)$ in arising \textbf{gauge group}
\end{itemize}
\end{column}
\begin{tikzpicture}[remember picture, overlay]
\node[anchor=base] at (3em,-3.75em) {\includegraphics[width=0.3\linewidth]{img/cy}};
\end{tikzpicture}
\begin{column}{0.3\linewidth}
% \centering
% \includegraphics[width=0.9\columnwidth]{img/cy}
\end{column}
\end{columns}
\end{block}
\pause
\begin{columns}
\begin{column}[t]{0.5\linewidth}
\highlight{Kähler manifolds} $\qty( M,\, g )$ such that
\begin{itemize}
\item $\dim\limits_{\mathds{C}} M = m$
\item $\mathrm{Hol}( g ) \subseteq \mathrm{SU}( m )$
\item $g$ is Ricci-flat (equiv.\ $c_1\qty( M )$ vanishes)
\end{itemize}
\end{column}
\pause
\begin{column}[t]{0.5\linewidth}
Characterised by \highlight{Hodge numbers}
\begin{equation*}
h^{r,\,s} = \dim\limits_{\mathds{C}} H_{\overline{\partial}}^{r,\,s}\qty( M,\, \mathds{C} )
\end{equation*}
counting the no.\ of harmonic $(r,\,s)$-forms.
\end{column}
\end{columns}
\end{frame}
\begin{frame}{D-branes and Open Strings}
Polyakov's action naturally introduces \highlight{Neumann b.c.:}
\begin{equation*}
\eval{\partial_{\upsigma} X\qty( \uptau, \upsigma )}_{\upsigma = 0}^{\upsigma = \ell} = 0
\end{equation*}
satisfied by \textbf{open and closed} strings living in $D$ dimensions s.t.\ $\square X = 0$.
\pause
\begin{equationblock}{T-duality}
\begin{equation*}
X( z, \overline{z} )
=
X( z ) + \overline{X}( \overline{z} )
\quad
\stackrel{T}{\Rightarrow}
\quad
X( z ) - \overline{X}( \overline{z} )
=
Y( z, \overline{z} )
=
Y( z ) + \overline{Y}( \overline{z} )
\end{equation*}
\end{equationblock}
\pause
Resulting effect (repeated $p \le D - 1$ times) leads to \highlight{Dirichlet b.c.:}
\begin{equation*}
\eval{\partial_{\upsigma} X^i\qty( \uptau, \upsigma )}_{\upsigma = 0}^{\upsigma = \ell} = 0
\quad
\stackrel{T}{\Rightarrow}
\quad
\eval{\partial_{\uptau} Y^i\qty( \uptau, \upsigma )}_{\upsigma = 0}^{\upsigma = \ell} = 0
\quad
\forall i = 1, 2,\, \dots,\, p
\end{equation*}
thus \textbf{open strings} can be \textbf{constrained} to \highlight{$D(D - p - 1)$-branes.}
\end{frame}
\begin{frame}{D-branes and Open Strings}
Introducing $Dp$-branes breaks \highlight{$\mathrm{ISO}(1,\, D-1) \rightarrow \mathrm{ISO}( 1, p ) \otimes \mathrm{SO}( D - 1 - p )$.}
\pause
\begin{equationblock}{Massless Spectrum (\emph{irrep} of \textbf{little group} $\mathrm{SO}( D - 2 )$}
\begin{equation*}
\mathcal{A}^{\upmu}
\quad \leftrightarrow \quad
\alpha_{-1}^{\upmu} \ket{0}
\qquad
\longrightarrow
\qquad
\begin{tabular}{@{}llll@{}}
$\mathcal{A}^A$
&
$\leftrightarrow$
&
$\alpha_{-1}^A \ket{0},$
&
$A = 0,\, 1,\, \dots,\, p$
\\
$\mathcal{A}^a$
&
$\leftrightarrow$
&
$\alpha_{-1}^a \ket{0},$
&
$a = 1,\, 2,\, \dots,\, D - p - 1$
\end{tabular}
\end{equation*}
\end{equationblock}
\pause
\begin{columns}
\begin{column}{0.5\linewidth}
\centering
\resizebox{0.55\columnwidth}{!}{\import{img}{chanpaton.pgf}}
\end{column}
\begin{column}{0.5\linewidth}
Introducing \textbf{Chan--Paton factors} $\tensor{\uplambda}{^r_{ij}}$, when branes are \textbf{coincident}:
\begin{equation*}
\bigoplus\limits_{r = 1}^N \mathrm{U}_r(1)
\quad
\longrightarrow
\quad
\mathrm{U}( N )
\end{equation*}
\pause
\highlight{Build gauge bosons, fermions and scalars.}
\end{column}
\end{columns}
\end{frame}
\begin{frame}{Standard Model-like Scenarios}
\centering
\resizebox{0.8\linewidth}{!}{\import{img}{smbranes.pgf}}
\end{frame}
\subsection[D-branes at Angles]{D-branes Intersecting at Angles}
\begin{frame}{Intersecting D-branes}
Consider \highlight{$N$ intersecting $D6$-branes} filling $\mathscr{M}^{1,3}$ and \textbf{embedded in} $\mathds{R}^6$
\begin{equationblock}{Twist Fields Correlators}
\begin{equation*}
\left\langle \prod\limits_{t = 1}^{N_B} \upsigma_{\mathrm{M}_{(t)}}\qty( x_{(t)} ) \right\rangle
=
\mathcal{N}\qty( \qty{ x_{(t)},\, \mathrm{M}_{(t)} }_{1 \le t \le N_B} )
e^{- S_{E\, (\text{cl})}\qty( \qty{ x_{(t)},\, \mathrm{M}_{(t)} }_{1 \le t \le N_B} )}
\end{equation*}
\end{equationblock}
\pause
\begin{tikzpicture}[remember picture, overlay]
\draw[line width=4pt, red] (29.5em,3.5em) ellipse (2cm and 1cm);
\end{tikzpicture}
\pause
\begin{columns}
\begin{column}{0.5\linewidth}
\centering
\resizebox{0.5\columnwidth}{!}{\import{img}{branesangles.pgf}}
\end{column}
\begin{column}{0.5\linewidth}
D-branes in \textbf{factorised} internal space:
\begin{itemize}
\item \textbf{embedded as lines} in $\mathds{R}^2 \times \mathds{R}^2 \times \mathds{R}^2$
\item \textbf{relative rotations} are $\mathrm{SO}(2) \simeq \mathrm{U}(1)$ elements
\item $S_{E\, (\text{cl})}\qty( \qty{ x_{(t)},\, \mathrm{M}_{(t)} }_{1 \le t \le N_B} ) \sim \text{Area}\qty( \qty{ f_{(t)},\, \mathrm{R}_{(t)} }_{1 \le t \le N_B} )$
\end{itemize}
\end{column}
\end{columns}
\end{frame}
\begin{frame}{$\mathrm{SO}(4)$ Rotations}
Consider \highlight{$\mathds{R}^4 \times \mathds{R}^2$} (focus on $\mathds{R}^4$):
\pause
\begin{columns}
\begin{column}{0.5\linewidth}
\centering
\resizebox{0.9\columnwidth}{!}{\import{img}{welladapted.pgf}}
\end{column}
\begin{column}{0.6\linewidth}
\begin{equation*}
\qty( X_{(t)} )^I
=
\tensor{\qty( R_{(t)} )}{^I_J}\, X^J - g_{(t)}^I
\quad
\text{s.t.}
\quad
R_{(t)} \in \frac{\mathrm{SO}(4)}{\mathrm{S}\qty( \mathrm{O}(2) \times \mathrm{O}(2) )}
\end{equation*}
\pause
that is
\begin{equation*}
\qty[ R_{(t)} ]
=
\qty{ R_{(t)} \sim \mathcal{O}_{(t)} R_{(t)} }
\end{equation*}
\end{column}
\end{columns}
\end{frame}
\begin{frame}{Boundary Conditions}
What are the consequences for \highlight{open strings?}
\pause
\begin{columns}
\begin{column}{0.6\linewidth}
\begin{itemize}
\item consider $u = x + i y = e^{\uptau_e + i \upsigma}$ and $\overline{u} = u^*$
\item let $x_{(t)} < x_{(t-1)}$ be the \textbf{worldsheet intersection points} on \textbf{real axis}
\item $X_{(t)}^{1,\, 2}$ are \textbf{Neumann}, $X_{(t)}^{3,\, 4}$ are \textbf{Dirichlet}
\end{itemize}
\end{column}
\begin{column}{0.4\linewidth}
\centering
\resizebox{0.9\columnwidth}{!}{\import{img}{branchcuts.pgf}}
\end{column}
\end{columns}
\pause
\begin{equationblock}{Branch Cuts and Discontinuities for $x \in D_{(t)}$}
\begin{equation*}
\begin{cases}
\partial_u X( x + i 0^+ )
& =
U_{(t)}
\cdot
\partial_{\overline{u}} \overline{X}( x - i 0^+ )
=
\qty[%
R_{(t)}^{-1}
\cdot
\qty( \upsigma_3 \otimes \mathds{1}_2 )
\cdot
R_{(t)}
]
\cdot
\partial_{\overline{u}} \overline{X}( x - i 0^+ )
\\
X( x_{(t)},\, x_{(t)} )
& =
f_{(t)}
\end{cases}
\end{equation*}
\end{equationblock}
\end{frame}
\section[Time Divergences]{Cosmological Backgrounds and Divergences}
\begin{frame}{BBB}
b
\end{frame}
\section[Deep Learning]{Deep Learning the Geometry of String Theory}
\begin{frame}{CCC}
c
\end{frame}
\end{document}