Let me present interdisciplinary collaborations related to the planet earth that I like because of mathematicians who are really interested by science in general and interested to contribute to real interdisciplinary breakthroughs. Of course they are just examples and it is impossible to be exhaustive. For other interdisciplinary collaborations related to fluid mechanics by D. Bresch and collaborators, it is possible to consult the part: Maths and Fluid Mechanics. Mathematicians who are interested to appear on this web-page may contact D. Bresch with a short description of the questions arising from other disciplines, their interdisciplinary collaboration and the explanation of the mathematics which are involved. Interested readers may also consult the texts in French on the website mathsmonde.math.cnrs.fr

0) COVID19 and MODELIZATION:

In the context of the health crisis, The CNRS National Institute in Maths and their Interactions (INSMI) sets up a plateform for coordinating actions on modelization and COVID19 (universities, CNRS, INRAE, Inserm, IRD…). : MODCOV19 This is a very important initiative to promote scientific interactions and coordinations.

I) AUVERGNE-RHÔNE-ALPES:

**ICJ UMR 5208 — UMPA UMR 5669 — IEES UMR IRD INRA :**

V. Calvez works with H. Hivert and F. Debarre on mathematical models related to biology. They have obtained the ERC consolidator grant Wacondy starting in 2021. The project focuses on mathematically well formulated problems such as collective motions of cells or the adaptation of a population to the change of the environment.

**UMPA UMR 5669 — LabPhys UMR5672 : **

L. Saint-Raymond works with L Chevillard and Th. Dauxois and several collaborators (mathematicians and Physicists from France and USA) on wave turbulence theory. They have obtained a Simons collaboration grant for it. It concerns Wave Kinetic Equation and its range of applicability. They also organize working groups and summer-schools to develop real interactions and diffusion of concepts between different communities.

**UMPA UMR 5669 — INRAE : **

P. Vigneaux works with G. Chambon and several collaborators on the modelization and numerical simulation of visco-plastic flows to understand the fluid-solid transition zones. It concerns also joint simulations and experimental studies of visco-plastic dam breaks on complex topographies. They got several grants including CNRS Tellus and CNRS infinity grants.

**LBMP — Clervolc:**

ClerVolc is a centre for research, innovation and training in the fields of volcanic processes, hazards and risk. It was financed in 2011 for 10 years under the French government ‘Laboratory of Excellence’ initiative, and then again in 2019 for a further 5 years. The ClerVolc project involves collaboration between five laboratories of Clermont-Auvergne University–CNRS including the LBMP (Laboratoire de Mathématique Blaise Pascal), and the Clermont-Ferrand Earth Physics Observatory, under the leadership of the Volcanology Laboratory of Clermont-Auvergne University. Since 2017 ClerVolc is also a component of the CAP 20-25 I-Site project, a large multidisciplinary project in higher education and international research involving a large number of public and private stakeholders.

The key collaborations of Clervolc with the LMBP focus on

- multiphasic flows as approximation of pyroclastic flows, where the difficulties resume to find a sufficient simple model in order to 1) be able to give a mathematical analysis of its main properties ; 2) to give efficient numerical approximations ; and sufficiently complex to be physicaly relevant. Collaboration between L. Chupin, T. Dubois (LMBP) and K. Khelfoun, O. Roche (LMV).
- statistical estimation of mass flow rate of volcanoes eruption using plume height, chemical properties and satellite observations and social and economic consequences. Collaboration between N. Azzaoui, A. Guillin (LMBP), J. Eychenne, M. Gouhier (LMV).

**LJK — ISTerre:**

An example of interdisciplinary working group: The SEISCOPE project gathers members from Grenoble Earth Sciences laboratory ISTerre and applied mathematics laboratory LJK. It is co-leaded by R. Brossier (ISTerre) and L. Métivier (LJK). It focuses on the development and analysis of high resolution seismic imaging methods, amenable to exploit the high quality high density seismic data made available by modern acquisition systems. Such development requires a broad expertise from geophysics, physics of wave propagation, numerical modeling, optimization, mathematics of inverse problems, and high performance computing. Gathering this broad expertise has been possible only through a long-term interaction between geophysicists from ISTerre and applied mathematicians from LJK.

**LJK INRIA AIrsea — Several meteorologic, oceanographic and data assimilation research centres worldwide.
**

The general scope of the AIRSEA project-team managed by L. Debreu is to develop *mathematical and computational methods for the modeling of oceanic and atmospheric flows*. The used mathematical tools involve both *deterministic and statistical approaches*. The domains of applications range from climate modeling to the prediction of extreme events. It concerns sever

**LAMA UMR 5127 — LOCIE:**

D. Bresch works with C. Ruyer-Quil and several collaborators (from LAMA and LOCIE) on free surface and instabilities. They got for instance the ANR Fraise to study how to optimize energy conversion through falling-film absorption processes. Its main technological outcome is the development of innovative concepts for the design of efficient desorbers, which represents the bottleneck for the conception of new compact absorption machines adapted to automotive air-conditioning, and more generally to the design of efficient heat pumps, chillers and recovery systems to limit energy waste. They also develop other studies related to free surface and capillarity effects related to H2020 contract with St Gobain and with collaborators and friends from INSA Toulouse and INRAE

**LAMA UMR 5127 — LECA UGA:**

J. Garnier and L Vuillon (LAMA Univ Savoie Mont-Blanc) are involved in a ANR project GlobNets leaded by W. Thullier (LECA Univ Grenoble Alpes). This project aims to decipher multi-trophic assemblages at biogeographic scales and to understand their responses to environmental changes or human activities. In particular, they formulate new mathematical model to use environmental DNA metabarcoding data, collected across thirteen distinct forest sites around the globe (tropical, temperate and boreal forests), to quantify the effects of these environmental changes on species interactions and predicts the ecological consequences of such changes.

II) OTHER REGIONS IN FRANCE :

**LAMA UMR8050 — IPGP : **

F. Bouchut works, from a long time ago, with A. Mangeney and several collaborators (mathematicians and geophysicists) on Landslides and granular flows. They got several grants including an ERC Consolidator grant (PI A. Mangeney) from 2014 to 2019. They developed appropriate reduced models and their numerical exploitations with the objective of real geophysical applications.

**IMB UMR5251 — EPOC UMR5805 **:

D. Lannes works, from a long-time ago, with Ph. Bonneton and several collaborators (mathematicians and physicists) on the propagation of waves and tsunamis in the presence of shorelines and more recently on the dynamic of floating bodies with the BCAM Bilbao and Tecnalia . This is a crucial subject for the development of new marine energies. They also organize the working group mathocéan.

**INSA Toulouse — SHOM: **

For the past ten years, P. Noble, J.-P. Vila (IMT-INSA Toulouse), F. Couderc (CNRS) and their collaborators A. Durand (Université Lyon 1), M. Parisot (INRIA), D. Bresch (CNRS and Univ. Savoie Mont-Blanc), G. Richard (IRSTEA), M. Kazakova (INSA Rouen), V. Michel Dansac (post doc) work in collaboration with SHOM (Service Hydrographic and Oceanography of the Navy) on the improvement of a regional version (Golfe de gascogne, Mediterranéen) of the calculation code HYCOM. The HYCOM code is essentially a multi-layered Saint-Venant code and the issues concern the implementation of « low mach » schemes to get rid of too restrictive time step conditions, the development of adapted boundary conditions to take into account different forcing (swell, atmosphere), the consideration of non-hydrostatic effects (Green-Naghdi, Boussines model type) or complex topographies (2d-1d models).

**CMAP – MnHn – Veolia environnement:**

S. Méléard is the head of a chair with the aim to develop synergy between applied maths and ecology around biodiversity. It concerns the modelization of ecosystems in order better understand important questions related to the environment such as ecological niches, adaptive evolution, spatial colonization, analysis of community dynamics and construction of biodiversity scenarios.

**ENS – PSL University / University Paris Saclay – LCPP**:

**UMR CNRS 7343 / Maths-Mechanics-Physics interactions**:

**DMA ENS PSL (INSU-INSMI)**:

**Ange team INRIA-LJLL:**

**LJLL ERC BLOC:**