{"id":4208,"date":"2022-06-24T17:57:16","date_gmt":"2022-06-24T15:57:16","guid":{"rendered":"https:\/\/samovar2022.int-evry.fr\/?p=4208"},"modified":"2022-06-24T19:03:18","modified_gmt":"2022-06-24T17:03:18","slug":"seminaire-de-basile-grammaticos-comment-etre-discret-le-16-07-2022-a-14h-salle-4a467-site-palaiseau","status":"publish","type":"post","link":"https:\/\/samovar.telecom-sudparis.eu\/index.php\/2022\/06\/24\/seminaire-de-basile-grammaticos-comment-etre-discret-le-16-07-2022-a-14h-salle-4a467-site-palaiseau\/","title":{"rendered":"S\u00e9minaire de Basile Grammaticos, \u00ab\u00a0Comment \u00eatre discret\u00a0\u00bb, le 16\/06\/2022 \u00e0 14h – Salle 4A467 site Palaiseau"},"content":{"rendered":"\t\t
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Le laboratoire Samovar a le plaisir de vous inviter au s\u00e9minaire Tipic pr\u00e9sent\u00e9 par Basile Grammaticos, le jeudi 16 Juin 2022 \u00e0 14h salle 4A467, \u00e0 Palaiseau.<\/p>

Titre\u00a0: <\/strong> Comment e\u0302tre discret\u00a0?<\/p>

Re\u0301sume\u0301<\/strong><\/p>

La question de la nature continue ou discre\u0300te de l\u2019espace-temps a pre\u0301occupe\u0301 les philosophes depuis l\u2019antiquite\u0301. Les deux noms qui sont souvent associe\u0301s a\u0300 cette question sont ceux de Ze\u0301non d\u2019Ele\u0301e (connu pour ses paradoxes) et De\u0301mocrite d\u2019Abdera (conside\u0301re\u0301 comme le pe\u0300re de la the\u0301orie atomique).<\/p>

Avec le de\u0301veloppement du formalisme diffe\u0301rentiel et inte\u0301gral la question est passe\u0301e en arrie\u0300re plan et il a e\u0301te\u0301 tacitement accepte\u0301 que les lois physiques peuvent s\u2019exprimer sous forme diffe\u0301rentielle.
Toutefois quand il s\u2019agit de simulations nume\u0301riques il est impe\u0301ratif de travailler avec une version discre\u0300te du mode\u0300le continu (diffe\u0301rentiel). Il se pose alors la question du meilleur choix d\u2019une telle version.<\/p>

Dans ma pre\u0301sentation je vais insister sur le fait qu\u2019il existe des approches parfaitement adapte\u0301es a\u0300 la construction d\u2019un syste\u0300me discret a\u0300 partir du mode\u0300le continu, e\u0301vitant le recours a\u0300 des inte\u0301grateurs de type boi\u0302te noire. Plusieurs exemples, faisant intervenir des syste\u0300mes comme logistique, Lotka-Volterra, SIR et le mode\u0300le HANDY vont e\u0301tayer mon argument. Pour moi, une bonne discre\u0301tisation est une qui a) pre\u0301serve la positivite\u0301 lorsque les solutions du syste\u0300me en question sont sense\u0301es e\u0302tre positives et b) fonctionne me\u0302me pour des pas de discre\u0301tisation pas ne\u0301cessairement petits.<\/p>

Les noms de R. Mickens et R. Hirota sont souvent associe\u0301s a\u0300 l\u2019approche de discre\u0301tisation de syste\u0300mes continus\u00a0: je re\u0301sumerai leurs recommandations.
La conclusion de mon travail sur les syste\u0300mes discrets est que ce sont eux les syste\u0300mes fondamentaux\u00a0: les syste\u0300mes continus en sont obtenus comme limite lorsque le pas de discre\u0301tisation tend vers ze\u0301ro. Et, chose tre\u0300s inte\u0301ressante, il existe aussi une autre limite quand le pas tend vers l\u2019infini\u00a0: elle donne naissance a\u0300 des syste\u0300mes de type automate cellulaire. A la fin de ma pre\u0301sentation je vais revenir sur la question de la nature de l\u2019espace temps a\u0300 la lumie\u0300re de la the\u0301orie des champs quantique, ou\u0300 il est souvent suppose\u0301 qu\u2019il existe une longueur minimale en dessous de laquelle la physique \u00ab\u00a0connue\u00a0\u00bb cesse d\u2019e\u0302tre applicable.<\/p>

Biographie\u00a0: <\/strong>
Basile Grammaticos est Directeur de Recherche au CNRS (\u00e9m\u00e9rite) et travaille dans le P\u00f4le Sant\u00e9 du Laboratoire Ir\u00e8ne Joliot-Curie. Initialement sp\u00e9cialiste en structure nucl\u00e9aire, il s\u2019est par la suite r\u00e9orient\u00e9 vers l\u2019\u00e9tude des syst\u00e8mes dynamiques o\u00f9, en collaboration avec Alfred Ramani, il est devenu un des pionniers du domaine de syst\u00e8mes discrets int\u00e9grables. En rejoignant le laboratoire IMNC (int\u00e9gr\u00e9 depuis dans l\u2019IJCLab) il a \u00e9tendu son domaine d\u2019int\u00e9r\u00eat aux applications de la physique dans la mod\u00e9lisation de syst\u00e8mes biologiques. Le s\u00e9minaire sur les techniques de discr\u00e9tisation est inspir\u00e9 par ses travaux sur les syst\u00e8mes discrets int\u00e9grables, les r\u00e9sultats pr\u00e9sent\u00e9s \u00e9tant, d\u2019une certaine fa\u00e7on, un sous-produit de la foison de r\u00e9sultats obtenus dans ce domaine.<\/p><\/div><\/div>

\u00a0<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<\/div>\n\t\t","protected":false},"excerpt":{"rendered":"

Le laboratoire Samovar a le plaisir de vous inviter au s\u00e9minaire Tipic pr\u00e9sent\u00e9 par Basile Grammaticos, le jeudi 16 Juin 2022 \u00e0 14h salle 4A467, \u00e0 Palaiseau. Titre : Comment e\u0302tre discret ? Re\u0301sume\u0301 La question de la nature continue ou discre\u0300te de l\u2019espace-temps a pre\u0301occupe\u0301 les philosophes depuis l\u2019antiquite\u0301. Les deux noms qui sont souvent associe\u0301s […]<\/p>\n","protected":false},"author":4,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"ocean_post_layout":"","ocean_both_sidebars_style":"","ocean_both_sidebars_content_width":0,"ocean_both_sidebars_sidebars_width":0,"ocean_sidebar":"0","ocean_second_sidebar":"0","ocean_disable_margins":"enable","ocean_add_body_class":"","ocean_shortcode_before_top_bar":"","ocean_shortcode_after_top_bar":"","ocean_shortcode_before_header":"","ocean_shortcode_after_header":"","ocean_has_shortcode":"","ocean_shortcode_after_title":"","ocean_shortcode_before_footer_widgets":"","ocean_shortcode_after_footer_widgets":"","ocean_shortcode_before_footer_bottom":"","ocean_shortcode_after_footer_bottom":"","ocean_display_top_bar":"default","ocean_display_header":"default","ocean_header_style":"","ocean_center_header_left_menu":"0","ocean_custom_header_template":"0","ocean_custom_logo":0,"ocean_custom_retina_logo":0,"ocean_custom_logo_max_width":0,"ocean_custom_logo_tablet_max_width":0,"ocean_custom_logo_mobile_max_width":0,"ocean_custom_logo_max_height":0,"ocean_custom_logo_tablet_max_height":0,"ocean_custom_logo_mobile_max_height":0,"ocean_header_custom_menu":"0","ocean_menu_typo_font_family":"0","ocean_menu_typo_font_subset":"","ocean_menu_typo_font_size":0,"ocean_menu_typo_font_size_tablet":0,"ocean_menu_typo_font_size_mobile":0,"ocean_menu_typo_font_size_unit":"px","ocean_menu_typo_font_weight":"","ocean_menu_typo_font_weight_tablet":"","ocean_menu_typo_font_weight_mobile":"","ocean_menu_typo_transform":"","ocean_menu_typo_transform_tablet":"","ocean_menu_typo_transform_mobile":"","ocean_menu_typo_line_height":0,"ocean_menu_typo_line_height_tablet":0,"ocean_menu_typo_line_height_mobile":0,"ocean_menu_typo_line_height_unit":"","ocean_menu_typo_spacing":0,"ocean_menu_typo_spacing_tablet":0,"ocean_menu_typo_spacing_mobile":0,"ocean_menu_typo_spacing_unit":"","ocean_menu_link_color":"","ocean_menu_link_color_hover":"","ocean_menu_link_color_active":"","ocean_menu_link_background":"","ocean_menu_link_hover_background":"","ocean_menu_link_active_background":"","ocean_menu_social_links_bg":"","ocean_menu_social_hover_links_bg":"","ocean_menu_social_links_color":"","ocean_menu_social_hover_links_color":"","ocean_disable_title":"default","ocean_disable_heading":"default","ocean_post_title":"","ocean_post_subheading":"","ocean_post_title_style":"","ocean_post_title_background_color":"","ocean_post_title_background":0,"ocean_post_title_bg_image_position":"","ocean_post_title_bg_image_attachment":"","ocean_post_title_bg_image_repeat":"","ocean_post_title_bg_image_size":"","ocean_post_title_height":0,"ocean_post_title_bg_overlay":0.5,"ocean_post_title_bg_overlay_color":"","ocean_disable_breadcrumbs":"default","ocean_breadcrumbs_color":"","ocean_breadcrumbs_separator_color":"","ocean_breadcrumbs_links_color":"","ocean_breadcrumbs_links_hover_color":"","ocean_display_footer_widgets":"default","ocean_display_footer_bottom":"default","ocean_custom_footer_template":"0","ocean_post_oembed":"","ocean_post_self_hosted_media":"","ocean_post_video_embed":"","ocean_link_format":"","ocean_link_format_target":"self","ocean_quote_format":"","ocean_quote_format_link":"post","ocean_gallery_link_images":"off","ocean_gallery_id":[],"footnotes":""},"categories":[286,438,543,578,282,608],"tags":[],"class_list":["post-4208","post","type-post","status-publish","format-standard","hentry","category-fractualites-ennews-fr","category-istec-fr","category-seminaire-istec","category-seminaire-istec-2020","category-seminaires-2020-fr","category-seminaires-istec-2","entry"],"_links":{"self":[{"href":"https:\/\/samovar.telecom-sudparis.eu\/index.php\/wp-json\/wp\/v2\/posts\/4208","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/samovar.telecom-sudparis.eu\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/samovar.telecom-sudparis.eu\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/samovar.telecom-sudparis.eu\/index.php\/wp-json\/wp\/v2\/users\/4"}],"replies":[{"embeddable":true,"href":"https:\/\/samovar.telecom-sudparis.eu\/index.php\/wp-json\/wp\/v2\/comments?post=4208"}],"version-history":[{"count":6,"href":"https:\/\/samovar.telecom-sudparis.eu\/index.php\/wp-json\/wp\/v2\/posts\/4208\/revisions"}],"predecessor-version":[{"id":4217,"href":"https:\/\/samovar.telecom-sudparis.eu\/index.php\/wp-json\/wp\/v2\/posts\/4208\/revisions\/4217"}],"wp:attachment":[{"href":"https:\/\/samovar.telecom-sudparis.eu\/index.php\/wp-json\/wp\/v2\/media?parent=4208"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/samovar.telecom-sudparis.eu\/index.php\/wp-json\/wp\/v2\/categories?post=4208"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/samovar.telecom-sudparis.eu\/index.php\/wp-json\/wp\/v2\/tags?post=4208"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}