Large Deviations rate function and Cramérs Theorem












1












$begingroup$


Given $X_1,...$ of iid random variables. We know that if the moment generating function $M(theta) < infty, forall theta $ from Cramérs Theorem we get:



$lim_{nto infty} frac{1}{n}log mathbb{P}(S_n ge na) = -I(a)$ where



$I(a) = sup_theta(atheta - log M(theta))$.



Question: What happens if $M(theta)$ isn't finite for all values of $theta$? Namely, is there another version of Cramérs theorem to help when calculating the rate function $I$ when this situation comes up.










share|cite|improve this question











$endgroup$

















    1












    $begingroup$


    Given $X_1,...$ of iid random variables. We know that if the moment generating function $M(theta) < infty, forall theta $ from Cramérs Theorem we get:



    $lim_{nto infty} frac{1}{n}log mathbb{P}(S_n ge na) = -I(a)$ where



    $I(a) = sup_theta(atheta - log M(theta))$.



    Question: What happens if $M(theta)$ isn't finite for all values of $theta$? Namely, is there another version of Cramérs theorem to help when calculating the rate function $I$ when this situation comes up.










    share|cite|improve this question











    $endgroup$















      1












      1








      1


      1



      $begingroup$


      Given $X_1,...$ of iid random variables. We know that if the moment generating function $M(theta) < infty, forall theta $ from Cramérs Theorem we get:



      $lim_{nto infty} frac{1}{n}log mathbb{P}(S_n ge na) = -I(a)$ where



      $I(a) = sup_theta(atheta - log M(theta))$.



      Question: What happens if $M(theta)$ isn't finite for all values of $theta$? Namely, is there another version of Cramérs theorem to help when calculating the rate function $I$ when this situation comes up.










      share|cite|improve this question











      $endgroup$




      Given $X_1,...$ of iid random variables. We know that if the moment generating function $M(theta) < infty, forall theta $ from Cramérs Theorem we get:



      $lim_{nto infty} frac{1}{n}log mathbb{P}(S_n ge na) = -I(a)$ where



      $I(a) = sup_theta(atheta - log M(theta))$.



      Question: What happens if $M(theta)$ isn't finite for all values of $theta$? Namely, is there another version of Cramérs theorem to help when calculating the rate function $I$ when this situation comes up.







      large-deviation-theory






      share|cite|improve this question















      share|cite|improve this question













      share|cite|improve this question




      share|cite|improve this question








      edited Jan 22 at 20:47







      all.over

















      asked Jan 22 at 20:24









      all.overall.over

      537




      537






















          1 Answer
          1






          active

          oldest

          votes


















          0












          $begingroup$

          Yes. Let $Theta$ be the set of $theta$ such that $M(theta)<infty$. It is easy to check that $Theta$ is convex, that is, an interval. As long as $theta$ is in the interior of $Theta$, and solves $M'(theta)/M(theta)=a$, that is, the maximization problem defining $I(a)$ is solved the calculus way, the conclusion holds for that value of $a$. The condition that you cite, that $Theta=mathbb R$, is introduced for convenience of exposition.



          I'm away from my books at the moment, so I can't give a reference to this version.






          share|cite|improve this answer









          $endgroup$













            Your Answer





            StackExchange.ifUsing("editor", function () {
            return StackExchange.using("mathjaxEditing", function () {
            StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix) {
            StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["$", "$"], ["\\(","\\)"]]);
            });
            });
            }, "mathjax-editing");

            StackExchange.ready(function() {
            var channelOptions = {
            tags: "".split(" "),
            id: "69"
            };
            initTagRenderer("".split(" "), "".split(" "), channelOptions);

            StackExchange.using("externalEditor", function() {
            // Have to fire editor after snippets, if snippets enabled
            if (StackExchange.settings.snippets.snippetsEnabled) {
            StackExchange.using("snippets", function() {
            createEditor();
            });
            }
            else {
            createEditor();
            }
            });

            function createEditor() {
            StackExchange.prepareEditor({
            heartbeatType: 'answer',
            autoActivateHeartbeat: false,
            convertImagesToLinks: true,
            noModals: true,
            showLowRepImageUploadWarning: true,
            reputationToPostImages: 10,
            bindNavPrevention: true,
            postfix: "",
            imageUploader: {
            brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
            contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
            allowUrls: true
            },
            noCode: true, onDemand: true,
            discardSelector: ".discard-answer"
            ,immediatelyShowMarkdownHelp:true
            });


            }
            });














            draft saved

            draft discarded


















            StackExchange.ready(
            function () {
            StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3083655%2flarge-deviations-rate-function-and-cram%25c3%25a9rs-theorem%23new-answer', 'question_page');
            }
            );

            Post as a guest















            Required, but never shown

























            1 Answer
            1






            active

            oldest

            votes








            1 Answer
            1






            active

            oldest

            votes









            active

            oldest

            votes






            active

            oldest

            votes









            0












            $begingroup$

            Yes. Let $Theta$ be the set of $theta$ such that $M(theta)<infty$. It is easy to check that $Theta$ is convex, that is, an interval. As long as $theta$ is in the interior of $Theta$, and solves $M'(theta)/M(theta)=a$, that is, the maximization problem defining $I(a)$ is solved the calculus way, the conclusion holds for that value of $a$. The condition that you cite, that $Theta=mathbb R$, is introduced for convenience of exposition.



            I'm away from my books at the moment, so I can't give a reference to this version.






            share|cite|improve this answer









            $endgroup$


















              0












              $begingroup$

              Yes. Let $Theta$ be the set of $theta$ such that $M(theta)<infty$. It is easy to check that $Theta$ is convex, that is, an interval. As long as $theta$ is in the interior of $Theta$, and solves $M'(theta)/M(theta)=a$, that is, the maximization problem defining $I(a)$ is solved the calculus way, the conclusion holds for that value of $a$. The condition that you cite, that $Theta=mathbb R$, is introduced for convenience of exposition.



              I'm away from my books at the moment, so I can't give a reference to this version.






              share|cite|improve this answer









              $endgroup$
















                0












                0








                0





                $begingroup$

                Yes. Let $Theta$ be the set of $theta$ such that $M(theta)<infty$. It is easy to check that $Theta$ is convex, that is, an interval. As long as $theta$ is in the interior of $Theta$, and solves $M'(theta)/M(theta)=a$, that is, the maximization problem defining $I(a)$ is solved the calculus way, the conclusion holds for that value of $a$. The condition that you cite, that $Theta=mathbb R$, is introduced for convenience of exposition.



                I'm away from my books at the moment, so I can't give a reference to this version.






                share|cite|improve this answer









                $endgroup$



                Yes. Let $Theta$ be the set of $theta$ such that $M(theta)<infty$. It is easy to check that $Theta$ is convex, that is, an interval. As long as $theta$ is in the interior of $Theta$, and solves $M'(theta)/M(theta)=a$, that is, the maximization problem defining $I(a)$ is solved the calculus way, the conclusion holds for that value of $a$. The condition that you cite, that $Theta=mathbb R$, is introduced for convenience of exposition.



                I'm away from my books at the moment, so I can't give a reference to this version.







                share|cite|improve this answer












                share|cite|improve this answer



                share|cite|improve this answer










                answered Jan 23 at 23:50









                kimchi loverkimchi lover

                11.1k31229




                11.1k31229






























                    draft saved

                    draft discarded




















































                    Thanks for contributing an answer to Mathematics Stack Exchange!


                    • Please be sure to answer the question. Provide details and share your research!

                    But avoid



                    • Asking for help, clarification, or responding to other answers.

                    • Making statements based on opinion; back them up with references or personal experience.


                    Use MathJax to format equations. MathJax reference.


                    To learn more, see our tips on writing great answers.




                    draft saved


                    draft discarded














                    StackExchange.ready(
                    function () {
                    StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3083655%2flarge-deviations-rate-function-and-cram%25c3%25a9rs-theorem%23new-answer', 'question_page');
                    }
                    );

                    Post as a guest















                    Required, but never shown





















































                    Required, but never shown














                    Required, but never shown












                    Required, but never shown







                    Required, but never shown

































                    Required, but never shown














                    Required, but never shown












                    Required, but never shown







                    Required, but never shown







                    Popular posts from this blog

                    Can a sorcerer learn a 5th-level spell early by creating spell slots using the Font of Magic feature?

                    Does disintegrating a polymorphed enemy still kill it after the 2018 errata?

                    A Topological Invariant for $pi_3(U(n))$