About

JiJi Fan is a faculty member involved in research within the Brown Physics Department and the Brown Theoretical Physics Center. Her research focuses on theoretical physics, with an emphasis on quantum field theory, quantum mechanics, and related areas. She supervises graduate and undergraduate students, guiding them through research projects that involve reproducing and extending results in physics literature, with an expectation for students to produce new, reasonable results within a short timeframe. Her mentorship includes overseeing students' progress through rigorous testing, such as comprehensive exams for PhD students, and supporting research activities that are often self-funded by students. Her previous members include postdoctoral researchers, PhD students, and undergraduate students, many of whom have gone on to prominent academic or research positions. She encourages students interested in working with her to contact her with their academic background and research experience.

Research topics

• Particle physics
• Physics
• Nuclear physics
• Astrophysics
• Astronomy
• Mathematics

Selected publications

• Chemically Modified Alginate Grafted Penicillanic Acid Derivatives for Antibacterial Electrospun Composite Nanofibers: Electrospinnability, Drug Delivery and Cytocompatibility

  Biomacromolecules · 2026-02-13

  article

  Electrospinning of pure alginate is challenging due to its rigid molecular conformation and high conductivity, while conventional blends with carrier polymers severely dilute its intrinsic bioactivity. To overcome this, we developed a chemical strategy to graft hydrophobic 6-aminopenicillanic acid (6-APA) onto alginate. Among three synthetic routes, the oxidative–reductive amination-derived alginate grafted penicillanic acid derivative (RA-OSA-APA) showed dramatically enhanced flexibility, with a 10-fold lower chain entanglement concentration and a 60-fold reduced rheological crossover frequency versus pristine alginate. Blending RA-OSA-APA with poly(vinyl alcohol) (PVA) enabled the production of bead-free nanofibers with high functional biopolymer content. These composite nanofibers exhibited high encapsulation efficiency (EE) for triclosan (TCA), tunable sustained release (73–86% over 810 min), excellent cell viability (>85%), and potent antibacterial activity against Staphylococcus aureus and Escherichia coli. This work establishes oxidative–reductive amination as an effective method to concurrently solve alginate’s electrospinning processability issue and engineer advanced multifunctionality for bioactive wound dressings.

  PublisherDOI

• Electrospun multilayer nanofibers with modified antibacterial alginate derivative for enhanced spinnability and drug sustained release

  Colloids and Surfaces B Biointerfaces · 2026-02-24

  article1st author
  PublisherDOI

• Exotic Higgs Decays at a Muon Collider

  arXiv (Cornell University) · 2026-04-07

  preprintOpen access1st authorCorresponding

  We study the sensitivity of a future muon collider to exotic Higgs decays in a minimal scenario of Standard Model (SM) augmented with a light singlet scalar $S$. We consider the decay $h\to SS$ and $S$'s subsequently decay back to SM. In particular, we focus on final states with four bottom quarks ($4b$), or two bottom quarks and two muons ($2b2μ$). Analyses are performed for two muon collider benchmark configurations: center-of-mass collision energy $\sqrt{s}=3~\mathrm{TeV}$ with $1~\mathrm{ab}^{-1}$ data and $\sqrt{s}=10~\mathrm{TeV}$ with $10~\mathrm{ab}^{-1}$ data. Machine-learning techniques are applied to suppress backgrounds and mitigate jet-combinatorics effects in both channels. We find that the $4b$ mode could be sensitive to the branching ratio, BR$(h \to SS \to 4b)$, of ${\cal O}(10^{-2})$ at 3 TeV and ${\cal O}(10^{-3})$ at 10 TeV, significantly improving upon high-luminosity LHC projections. In the Higgs-portal model with $S$ coupling to SM only through mixing with the Higgs, the sensitivities to BR$(h \to SS)$ remain at the same level given ${\cal O}(1)$ branching fraction of $S$ decaying into $b$-quarks. The $2b2μ$ mode benefits from a clean dimuon resonance and can probe BR$(h\to SS\to 2b2μ)$ down to $10^{-5}$ level at a 10 TeV muon collider. But the sensitivity to BR$(h \to SS)$ will be significantly reduced due to the small branching fraction of $S$ decaying into muons in the Higgs portal model.

  PublisherDOI

• Exotic Higgs Decays at a Muon Collider

  ArXiv.org · 2026-04-07

  articleOpen access1st authorCorresponding

  We study the sensitivity of a future muon collider to exotic Higgs decays in a minimal scenario of Standard Model (SM) augmented with a light singlet scalar $S$. We consider the decay $h\to SS$ and $S$'s subsequently decay back to SM. In particular, we focus on final states with four bottom quarks ($4b$), or two bottom quarks and two muons ($2b2μ$). Analyses are performed for two muon collider benchmark configurations: center-of-mass collision energy $\sqrt{s}=3~\mathrm{TeV}$ with $1~\mathrm{ab}^{-1}$ data and $\sqrt{s}=10~\mathrm{TeV}$ with $10~\mathrm{ab}^{-1}$ data. Machine-learning techniques are applied to suppress backgrounds and mitigate jet-combinatorics effects in both channels. We find that the $4b$ mode could be sensitive to the branching ratio, BR$(h \to SS \to 4b)$, of ${\cal O}(10^{-2})$ at 3 TeV and ${\cal O}(10^{-3})$ at 10 TeV, significantly improving upon high-luminosity LHC projections. In the Higgs-portal model with $S$ coupling to SM only through mixing with the Higgs, the sensitivities to BR$(h \to SS)$ remain at the same level given ${\cal O}(1)$ branching fraction of $S$ decaying into $b$-quarks. The $2b2μ$ mode benefits from a clean dimuon resonance and can probe BR$(h\to SS\to 2b2μ)$ down to $10^{-5}$ level at a 10 TeV muon collider. But the sensitivity to BR$(h \to SS)$ will be significantly reduced due to the small branching fraction of $S$ decaying into muons in the Higgs portal model.

  PublisherOA PDF

• Synergistic enhancement of polyvinyl alcohol coating via montmorillonite reinforcement and chemical cross-linking for high-barrier food packaging

  Applied Clay Science · 2026-03-10

  article
  PublisherDOI

• Programmable Fe3+-crosslinked alginate grafted β-cyclodextrin derivative/1-adamantaneethyl formate supramolecular microparticles with dual pH- and light-response: A materials chemistry strategy for intelligent drug delivery

  Materials Today Chemistry · 2026-03-07

  article
  PublisherDOI

• Engineering amphiphilic alginate derivatives for electrospun nanofibers: Interfacial self-assembly, enhanced electrospinnability and controlled drug delivery

  Colloids and Surfaces A Physicochemical and Engineering Aspects · 2026-01-04 · 1 citations

  article1st author
  PublisherDOI

• Pulse and Polarization Structures in Axion-Converted X-rays from Pulsars

  ArXiv.org · 2025-01-21

  preprintOpen access1st authorCorresponding

  Neutron stars (NS's) with their strong magnetic fields and hot dense cores could be powerful probes of axions, a classic benchmark of feebly-coupled new particles, through abundant production of axions with the axion-nucleon coupling and subsequent conversion into X-rays due to the axion-photon coupling. In this article, we point out that the pulsation structures in both the intensity and polarization of X-rays from NS's could provide us additional information about axions and their couplings. We develop new analytical formalisms of pulsation-polarization structure applicable to a wide range of NS's in the axion scenario and argue that they hold in complicated astrophysical environments. As a case study, we apply our formalism to a representative X-ray Dim Isolated Neutron Star, RX J1856.6-3754, with an unexpected hard X-ray excess which might be axion-induced. We show with an updated fit that the axion explanation is compatible with both the intensity and pulsation data available, and combining the pulsation data does not shift the posterior by more than $1\,σ$. Yet, the preferred parameter space is close to being excluded by other astrophysical constraints. With a 75% reduction of the uncertainties in the pulsation data, we could potentially draw a definite conclusion on the axion-induced X-rays at more than $3\,σ$ level.

  PublisherOA PDFDOI

• The Juno mission as a probe of long-range new physics

  Journal of High Energy Physics · 2025-01-21 · 1 citations

  articleOpen access

  A bstract Orbits of celestial objects, especially the geocentric and heliocentric ones, have been well explored to constrain new long-range forces beyond the Standard Model (SM), often referred to as fifth forces. In this paper, for the first time, we apply the motion of a spacecraft around Jupiter to probe fifth forces that don’t violate the equivalence principle. The spacecraft is the Juno orbiter, and ten of its early orbits already allow a precise determination of the Jovian gravitational field. We use the shift in the precession angle as a proxy to test non-gravitational interactions between Juno and Jupiter. Requiring that the contribution from the fifth force does not exceed the uncertainty of the precession shift inferred from data, we find that a new parameter space with the mass of the fifth-force mediator around 10 −14 eV is excluded at 95% C.L.

  PublisherOA PDFDOI

• Pulse and Polarization Structures in Axion-Converted X-Rays from Pulsars

  Physical Review Letters · 2025-11-12 · 1 citations

  articleOpen access1st authorCorresponding

  Neutron stars (NSs) with their strong magnetic fields and hot dense cores could be powerful probes of axions, a classic benchmark of feebly coupled new particles, through abundant production of axions with the axion-nucleon coupling and subsequent conversion into x-rays due to the axion-photon coupling. In this Letter, we point out that the pulsation structures in both the intensity and polarization of x-rays from NSs could provide us additional information about axions and their couplings. We develop new analytical formalisms of pulsation-polarization structure applicable to a wide range of NSs in the axion scenario and argue that they hold in complicated astrophysical environments. As a case study, we apply our formalism to a representative X-ray Dim Isolated Neutron Star, RX J1856.6-3754, with an unexpected hard x-ray excess which might be axion induced. We show with an updated fit that the axion explanation is compatible with both the intensity and pulsation data available, and combining the pulsation data does not shift the posterior by more than 1σ. Yet, the preferred parameter space is close to being excluded by other astrophysical constraints. With a 75% reduction of the uncertainties in the pulsation data, we could potentially draw a definite conclusion on the axion-induced x-rays at more than 3σ level.

  PublisherDOI

Frequent coauthors

• C. Collard

  Institut Pluridisciplinaire Hubert Curien

  1134 shared

• D. Blöch

  Institut Pluridisciplinaire Hubert Curien

  1134 shared

• J. Andreä

  Institut Pluridisciplinaire Hubert Curien

  1133 shared

• E. Conte

  Institut Pluridisciplinaire Hubert Curien

  1113 shared

• E. C. Chabert

  Institut Pluridisciplinaire Hubert Curien

  1085 shared

• A. Aubin

  International Institute of Tropical Agriculture

  982 shared

• M. Lethuillier

  Institute of Nuclear Physics of Lyon

  930 shared

• P. Verdier

  Institute of High Energy Physics

  918 shared

Labs

• JiJi Fan's LabPI

  Quantum field theory research

Education

• Ph.D., Theoretical Particle Physics

  Yale University

  2009

• B.S.

  University of Science and Technology of China

  2004