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Stochastic Processes and
Advanced Mathematical Finance
Homework 10 </title> 
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<h2 class="titleHead">Math 489/889<br />
Stochastic Processes and<br />
Advanced Mathematical Finance<br />
Homework 10 </h2>
<div class="author" ><span 
class="cmr-12x-x-120">Steve Dunbar</span></div><br />
<div class="date" ><span 
class="cmr-12x-x-120">December 6, 2010</span></div>
   </div>
      <ol  class="enumerate1" >
      <li 
  class="enumerate" id="x1-3x1">Simulate the solution of the stochastic differential equation
<div class="math-display"><!--l. 22--><math 
 xmlns="http://www.w3.org/1998/Math/MathML" display="block" ><mrow 
>
                       <mi 
>d</mi><mi 
>X</mi><mrow ><mo 
class="MathClass-open">(</mo><mrow><mi 
>t</mi></mrow><mo 
class="MathClass-close">)</mo></mrow> <mo 
class="MathClass-rel">=</mo> <mi 
>X</mi><mrow ><mo 
class="MathClass-open">(</mo><mrow><mi 
>t</mi></mrow><mo 
class="MathClass-close">)</mo></mrow><mi 
>d</mi><mi 
>t</mi> <mo 
class="MathClass-bin">+</mo> <mn>2</mn><mi 
>X</mi><mrow ><mo 
class="MathClass-open">(</mo><mrow><mi 
>t</mi></mrow><mo 
class="MathClass-close">)</mo></mrow><mi 
>d</mi><mi 
>W</mi>
</mrow></math></div>
      <!--l. 24--><p class="nopar" > on the interval <!--l. 24--><math 
 xmlns="http://www.w3.org/1998/Math/MathML" display="inline" ><mrow 
><mrow ><mo 
class="MathClass-open">[</mo><mrow><mn>0</mn><mo 
class="MathClass-punc">,</mo> <mn>1</mn></mrow><mo 
class="MathClass-close">]</mo></mrow></mrow></math>
                                                                          

                                                                          
      with initial condition <!--l. 24--><math 
 xmlns="http://www.w3.org/1998/Math/MathML" display="inline" ><mrow 
><mi 
>X</mi><mrow ><mo 
class="MathClass-open">(</mo><mrow><mn>0</mn></mrow><mo 
class="MathClass-close">)</mo></mrow> <mo 
class="MathClass-rel">=</mo> <mn>1</mn></mrow></math>
      and step size <!--l. 25--><math 
 xmlns="http://www.w3.org/1998/Math/MathML" display="inline" ><mrow 
><mi 
>&#x0394;</mi><mi 
>t</mi> <mo 
class="MathClass-rel">=</mo> <mn>1</mn><mo 
class="MathClass-bin">&#x2215;</mo><mn>1</mn><mn>0</mn></mrow></math>.
      Use the results of your coin-tossing record which was rescaled to <!--l. 26--><math 
 xmlns="http://www.w3.org/1998/Math/MathML" display="inline" ><mrow 
><msub><mrow 
><mi 
>&#x0174;</mi></mrow><mrow 
><mn>1</mn><mn>0</mn></mrow></msub 
><mrow ><mo 
class="MathClass-open">(</mo><mrow><mn>1</mn><mn>0</mn><mi 
>t</mi></mrow><mo 
class="MathClass-close">)</mo></mrow><mo 
class="MathClass-bin">&#x2215;</mo><msqrt><mrow><mn>1</mn><mn>0</mn></mrow></msqrt></mrow></math>
      as an approximation of <!--l. 27--><math 
 xmlns="http://www.w3.org/1998/Math/MathML" display="inline" ><mrow 
><mi 
>W</mi><mrow ><mo 
class="MathClass-open">(</mo><mrow><mi 
>t</mi></mrow><mo 
class="MathClass-close">)</mo></mrow></mrow></math>
      to create the 10 increments <!--l. 28--><math 
 xmlns="http://www.w3.org/1998/Math/MathML" display="inline" ><mrow 
><mi 
>d</mi><mi 
>W</mi></mrow></math>
      needed for the simulation.
      </p></li>
      <li 
  class="enumerate" id="x1-5x2">Find the solution of the stochastic differential equation
<div class="math-display"><!--l. 33--><math 
 xmlns="http://www.w3.org/1998/Math/MathML" display="block" ><mrow 
>
                        <mi 
>d</mi><mi 
>Y</mi> <mrow ><mo 
class="MathClass-open">(</mo><mrow><mi 
>t</mi></mrow><mo 
class="MathClass-close">)</mo></mrow> <mo 
class="MathClass-rel">=</mo> <mi 
>Y</mi> <mrow ><mo 
class="MathClass-open">(</mo><mrow><mi 
>t</mi></mrow><mo 
class="MathClass-close">)</mo></mrow><mi 
>d</mi><mi 
>t</mi> <mo 
class="MathClass-bin">+</mo> <mn>2</mn><mi 
>Y</mi> <mrow ><mo 
class="MathClass-open">(</mo><mrow><mi 
>t</mi></mrow><mo 
class="MathClass-close">)</mo></mrow><mi 
>d</mi><mi 
>W</mi>
</mrow></math></div>
      <!--l. 35--><p class="nopar" > by guessing and checking with It&#x00F4;&#x2019;s Formula.
      </p></li>
      <li 
  class="enumerate" id="x1-7x3">Find the mode (the value of the independent variable with the highest
      probability) of the lognormal probability density function. (Use parameters
      <!--l. 41--><math 
 xmlns="http://www.w3.org/1998/Math/MathML" display="inline" ><mi 
>&#x03BC;</mi></math>
      and <!--l. 41--><math 
 xmlns="http://www.w3.org/1998/Math/MathML" display="inline" ><mi 
>&#x03C3;</mi></math>.)
      </li>
      <li 
  class="enumerate" id="x1-9x4">
           <ol  class="enumerate2" >
           <li 
  class="enumerate" id="x1-11x1">Suppose you buy a stock (or more properly an index fund) whose
           value <!--l. 47--><math 
 xmlns="http://www.w3.org/1998/Math/MathML" display="inline" ><mi 
>S</mi><mrow ><mo 
class="MathClass-open">(</mo><mrow><mi 
>t</mi></mrow><mo 
class="MathClass-close">)</mo></mrow></math>
           is described by the stochastic differential equation <!--l. 48--><math 
 xmlns="http://www.w3.org/1998/Math/MathML" display="inline" ><mi 
>d</mi><mi 
>S</mi> <mo 
class="MathClass-rel">=</mo> <mn>0</mn> <mo 
class="MathClass-bin">&#x22C5;</mo> <mi 
>S</mi><mspace width="0em" class="thinspace"/><mi 
>d</mi><mi 
>t</mi> <mo 
class="MathClass-bin">+</mo> <mi 
>&#x03C3;</mi> <mo 
class="MathClass-bin">&#x22C5;</mo> <mi 
>S</mi><mspace width="0em" class="thinspace"/><mi 
>d</mi><mi 
>W</mi></math>
           corresponding  to  a  zero  compounded  growth  and  pure  market
           fluctuations proportional to the stock value. What are your chances
           to double your money?
                                                                          

                                                                          
           </li>
           <li 
  class="enumerate" id="x1-13x2">Suppose you buy a stock (or more properly an index fund) whose
           value <!--l. 54--><math 
 xmlns="http://www.w3.org/1998/Math/MathML" display="inline" ><mi 
>S</mi><mrow ><mo 
class="MathClass-open">(</mo><mrow><mi 
>t</mi></mrow><mo 
class="MathClass-close">)</mo></mrow></math>
           is described by the stochastic differential equation <!--l. 55--><math 
 xmlns="http://www.w3.org/1998/Math/MathML" display="inline" ><mi 
>d</mi><mi 
>S</mi> <mo 
class="MathClass-rel">=</mo> <msup><mrow 
><mi 
>&#x03C3;</mi></mrow><mrow 
><mn>2</mn></mrow></msup 
><mo 
class="MathClass-bin">&#x2215;</mo><mn>2</mn> <mo 
class="MathClass-bin">&#x22C5;</mo> <mi 
>S</mi><mspace width="0em" class="thinspace"/><mi 
>d</mi><mi 
>t</mi> <mo 
class="MathClass-bin">+</mo> <mi 
>&#x03C3;</mi> <mo 
class="MathClass-bin">&#x22C5;</mo> <mi 
>S</mi><mspace width="0em" class="thinspace"/><mi 
>d</mi><mi 
>W</mi></math>
           corresponding to a non-zero compounded growth and pure market
           fluctuations proportional to the stock value and the two parameter
           values are coincidentally connected in their value. What are your
           chances to double your money?</li></ol>
      </li></ol>
    
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