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Sampling metastable systems using collective variables and Jarzynski-Crooks paths
No full textInternational audienceWe consider the problem of sampling a high dimensional multimodal target probability measure. We assume that a good proposal kernel to move only a subset of the degrees of freedoms (also known as collective variables) is known a priori. This proposal kernel can for example be built using normalizing flows. We show how to extend the move from the collective variable space to the full space and how to implement an accept-reject step in order to get a reversible chain with respect to a target probability measure. The accept-reject step does not require to know the marginal of the original measure in the collective variable (namely to know the free energy). The obtained algorithm admits several variants, some of them being very close to methods which have been proposed previously in the literature. We show how the obtained acceptance ratio can be expressed in terms of the work which appears in the Jarzynski-Crooks equality, at least for some variants. Numerical illustrations demonstrate the efficiency of the approach on various simple test cases, and allow us to compare the variants of the algorithm
Policy Monitor Issue 18 No. 01 July-September 2025 on Harnessing Value Chains for Sustainable and Inclusive Growth
Get PDFThe articles in this edition focus on Kenya’s recent economic developments; strengthening the indigenous chicken value chain for sustainable livelihoods; strengthening the competitiveness of Kenya’s MSMEs’ leather and leather products value chains; and decoding the AI value chain for economic growth in Kenya.
This Edition highlights various activities undertaken by the Institute in the first quarter. Among the key activities are the side event on Advancing Social Equity, Inclusion, and Justice through Public Participation at the Devolution Conference, and the launch of the Kenya Country Economic Transformation Outlook Report.
Additionally, the Institute organized dissemination workshops, including one on Leveraging SDR for Sustaining Economic Recovery in Kenya and a validation workshop on the Follow-up National Survey on Unclaimed Financial Assets. Further, the Policy Monitor highlights several roundtables and stakeholder workshops held during this period on various thematic and interdisciplinary research areas, including a roundtable on the RESET Project and a National Policy Dialogue on Circularity and Used Textiles Trade in Kenya
Optimizing the diffusion coefficient of overdamped Langevin dynamics
No full textInternational audienceOverdamped Langevin dynamics are reversible stochastic differential equations which are commonly used to sample probability measures in high-dimensional spaces, such as the ones appearing in computational statistical physics and Bayesian inference. By varying the diffusion coefficient, there are in fact infinitely many overdamped Langevin dynamics which are reversible with respect to the target probability measure at hand. This suggests to optimize the diffusion coefficient in order to increase the convergence rate of the dynamics, as measured by the spectral gap of the generator associated with the stochastic differential equation. We analytically study this problem here, obtaining in particular necessary conditions on the optimal diffusion coefficient. We also derive an explicit expression of the optimal diffusion in some appropriate homogenized limit. Numerical results, both relying on discretizations of the spectral gap problem and Monte Carlo simulations of the stochastic dynamics, demonstrate the increased quality of the sampling arising from an appropriate choice of the diffusion coefficient
Observation of the open-charm tetraquark state in the decay
No full textInternational audienceAn amplitude analysis of decays is performed using proton-proton collision data, corresponding to an integrated luminosity of , collected with the LHCb detector at center-of-mass energies of 7, 8, and 13. A resonant structure of spin-parity is observed in the invariant-mass spectrum with a significance of . The mass and width of the state, modeled with a BreitWigner lineshape, are determined to be and respectively, where the first uncertainties are statistical and the second systematic. These properties and the quark content are consistent with those of the open-charm tetraquark state observed previously in the final state of the decay. This result confirms the existence of the state in a new decay mode. The state, reported in the decay, is also searched for in the invariant-mass spectrum of the decay, without finding evidence for it
Study of Λ0 b and Ξ0 b decays to Λh+h ′− and evidence for CP violation in Λ0 b → ΛK+K− decays
No full textInternational audienceA study of Λ 0 b and Ξ0 b decays to Λh+h ′− (h (′) = π, K) is performed using pp collision data collected by the LHCb experiment during LHC Runs 1–2, corresponding to an integrated luminosity of 9 fb−1 . The branching fractions for these decays are measured using the Λ 0 b → Λ + c (→ Λπ+)π − decay as control channel. The decays Λ 0 b → Λπ+π − and Ξ0 b → ΛK−π + are observed for the first time. For decay modes with sufficient signal yields, CP asymmetries are measured in the full and localized regions of the final-state phase space. Evidence is found for CP violation in the Λ 0 b → ΛK+K− decay, interpreted as originating primarily from an asymmetric Λ 0 b → N∗+K− decay amplitude. The measured CP asymmetries for the other decays are compatible with zero
Multi-wavelength study of OT 081: broadband modelling of a transitional blazar
No full textInternational audienceOT 081 is a well-known, luminous blazar that is remarkably variable in many energy bands. We present the first broadband study of the source which includes very-high-energy (VHE, 100 GeV) -ray data taken by the MAGIC and H.E.S.S. imaging Cherenkov telescopes. The discovery of VHE -ray emission happened during a high state of -ray activity in July 2016, observed by many instruments from radio to VHE -rays. We identify four states of activity of the source, one of which includes VHE -ray emission. Variability in the VHE domain is found on daily timescales. The intrinsic VHE spectrum can be described by a power-law with index (MAGIC) and (H.E.S.S.) in the energy range of 55--300 GeV and 120--500 GeV, respectively. The broadband emission cannot be sucessfully reproduced by a simple one-zone synchrotron self-Compton model. Instead, an additional external Compton component is required. We test a lepto-hadronic model that reproduces the dataset well and a proton-synchrotron dominated model that requires an extreme proton luminosity. Emission models that are able to successfully represent the data place the emitting region well outside of the Broad Line Region (BLR) to a location at which the radiative environment is dominated by the infrared thermal radiation field of the dusty torus. In the scenario described by this flaring activity, the source appears to be an FSRQ, in contrast with past categorizations. This suggests that the source can be considered to be a transitional blazar, intermediate between BL~Lac and FSRQ objects
Elliptic anisotropy measurement of the f(980) hadron in proton-lead collisions and evidence for its quark-antiquark composition
No full textInternational audienceDespite the f(980) hadron having been discovered half a century ago, the question about its quark content has not been settled: it might be an ordinary quark-antiquark () meson, a tetraquark () exotic state, a kaon-antikaon () molecule, or a quark-antiquark-gluon () hybrid. This paper reports strong evidence that the f(980) state is an ordinary meson, inferred from the scaling of elliptic anisotropies () with the number of constituent quarks (), as empirically established using conventional hadrons in relativistic heavy ion collisions. The f(980) state is reconstructed via its dominant decay channel f(980) , in proton-lead collisions recorded by the CMS experiment at the LHC, and its is measured as a function of transverse momentum (). It is found that the = 2 ( state) hypothesis is favored over = 4 ( or states) by 7.7, 6.3, or 3.1 standard deviations in the 10, 8, or 6 GeV/ ranges, respectively, and over = 3 ( hybrid state) by 3.5 standard deviations in the 8 GeV/ range. This result represents the first determination of the quark content of the f(980) state, made possible by using a novel approach, and paves the way for similar studies of other exotic hadron candidates
Signed tropicalization of polar cones
No full textInternational audienceWe study the tropical analogue of the notion of polar of a cone, working over the semiring of tropical numbers with signs. We characterize the cones which arise as polars of sets of tropically nonnegative vectors by an invariance property with respect to a tropical analogue of Fourier-Motzkin elimination. We also relate tropical polars with images by the nonarchimedean valuation of classical polars over real closed nonarchimedean fields and show, in particular, that for semi-algebraic sets over such fields, the operation of taking the polar commutes with the operation of signed valuation (keeping track both of the nonarchimedean valuation and sign). We apply these results to characterize images by the signed valuation of classical cones of matrices, including the cones of positive semidefinite matrices, completely positive matrices, completely positive semidefinite matrices, and their polars, including the cone of co-positive matrices, showing that hierarchies of classical cones collapse under tropicalization. We finally discuss an application of these ideas to optimization with signed tropical numbers
Wajir County Annual Development Plan 2025/2026
Get PDFThis is the Third County Annual Development Plan (CADP) in implementation of our transformative five-year County Integrated Development Plan (CIDP) 2023 - 2027. It is a crucial Plan in providing the direction that we must take to achieve the milestones and ambitious goals we have set for ourselves. The Plan comes at a time when we are in high gear towards implementing policies and programmes that are meant to enhance implementation of programmes and projects.
The programmes and projects in this CADP reflect the County and peoples’ priorities in the key sectors of Finance and Production; Health; Food Security; Water, Environment and Natural Resources; Early Childhood Development Education (ECDE) and Social Services. Through implementation of this plan, we endeavor to bring services closer to the people, uphold equity amongst all and most importantly start the journey to socio-economic transformation for all the people equitably and all settlements of Wajir County.
The allocation of resources available in the FY 2025/2026 has given due consideration to the proposals made by the Couty residents during public participation for the County Annual Development Plan (CADP) as well as Year three (3) targets of the CIDP. In that respect, Health Services; Agriculture; and Water, Environment and Natural Resources sectors have been allocated to address the needs and aspirations of the people. The allocation of resources has also reflected the aspirations in the the Governor’s Manifesto, Vision 2030 and global best practices specifically achievement of the SDGs
Kitui County Annual Development Plan 2026/2027
Get PDFThe Annual Development Plan (ADP) is prepared in accordance with Article 220 (2) of the constitution. The Public Finance Management Act, 2012, (section 126) requires each County Government to prepare ADP which is submitted for approval to the County Assembly not later than 1st September of each year. ADP provides county strategic priorities, programmes and projects to be offered to county citizens in the succeeding financial year and are selected from County Integrated Development plan (CIDP) 2023-2027. County Performance Review for the previous year (FY2024/2025)
Some of prominent achievements include; Community level infrastructure development programme – over three hundred projects have been done across the county benefiting three hundred households.
Disbursement of pro-poor was done to need students. Existing VTCs were renovated that; Kyuso VTC, Tseikuru VTC, Miambani VTC, Mwingi Baptist, Kanyongonyo VTC, Mutwaathi VTC, Kyatune VTC (Kyuso, Tseikuru, Miambani, Mwingi Central, Yatta Kwa Vonza, Migwani and Ikanga Kyatune) Fencing of land designated for Utalii College complete. Twambui Police station and Imuumba police station blocks were completed fenced and now are operational. Construction of Kyuso ward office is ongoing 80% complete. Construction of 80 sand dams completed and 9 sump wells constructed. 12 bore holes were drilled and equipped while 20 were repaired and equipped. 6 cluster irrigation projects completed and one solarized. 377 Parking slots marked in township ward to improve revenue. 59 posts of Streetlight installed in various places in township wards and its environs. 10,000 Households & Institutions were connected with electricity in partnership with REREC and Kenya Power. 144,000 tree seedlings were planted.
48 Solar Energy Integrated Security Lights installed in various markets across the county. Construction of Kitui County aggregation and Industrial Park (K-CAIP) ongoing. Construction of Ultra-Modern Stadium at Kivou and Kyoani is 70% complete. Kitui County Youth Development Policy done