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Wednesday, Feb 5, 2025
No colloquium: Department meeting

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Wednesday, Feb 12, 2025
No colloquium: faculty search meetings

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Wednesday, Feb 19, 2025
No colloquium: faculty search meetings

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Wednesday, Feb 26, 2025
No colloquium: faculty search meetings

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Wednesday, March 5, 2025
Nathan Harshman (American University)

Quantum Abacus: Anyons in One Dimension

The classical abacus is a digital computer that allows computation by manipulating the location of beads. Recent experimental advances with ultracold atoms in one dimensional optical traps motivate considering what a quantum abacus could do. In this talk, I use the possibility of a quantum abacus to explain and explore the ideas of topological quantum computing with anyons. Most proposals for topological quantum computers rely on the properties of braiding anyons in two dimensions. But is it possible to make a topological quantum computer in one dimension? Are anyons even possible in one dimension? The answer, recently confirmed by experiments, is yes: topological exchange statistics are possible in one dimension.

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Wednesday, March 12, 2025
No colloquium: faculty search meetings

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Wednesday, March 19, 2025
No colloquium -- Spring break

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Wednesday, March 26, 2025
Jose P. D’Incao (UMass Boston)

The complex nature of few-atom interactions: from Universality to Controlled Chemistry

Over the past few decades, advances in ultracold quantum gases have increasingly enabled precise control over atomic and molecular behavior, opening new frontiers in quantum science. Today’s experimental techniques allow for the precise preparation of quantum states and the tunability of interactions, granting access to a wide range of complex few-body phenomena with unprecedented detail. This progress has, for instance, made it possible to explore the strongly interacting regime, where unique and counterintuitive universal molecular states—such as Feshbach and Efimov molecules—emerge. Moreover, it has facilitated the study of controlled, state-to-state chemistry. In this talk, I will discuss these phenomena and highlight the exciting prospects they offer. These include the use of molecular states as a source of entangled atomic pairs for novel matter-wave interferometers, as well as controlled chemical reactions in non-equilibrium dynamics.  

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Wednesday, April 2, 2025
Lode Pollet (LMU Munich)

Quantum Simulation of Many-body physics with Rydberg systems: from supersolids to spin liquids

Rydberg tweezer arrays provide a versatile platform to explore quantum magnets. Different types of interactions, such as dipolar XY,  van-der-Waals Ising  ZZ, and spin-flip terms, can simultaneously exist.

Furthermore, the Rydberg blockade mechanism can be used to prevent the excitation of another, nearby-situated Rydberg atom akin to the Gauss law in lattice gauge theory.

In the talk I give an overview of the current state of the art and report on two different types of physics that can be realized with such platforms.

First, I comment on a recent experiment which exploited the blockade mechanism in order to observe the onset of a dynamically prepared, gapped Z2 quantum spin liquid on the ruby lattice (Semgehini et al, Science 374, 1242 (2021)). The thermodynamic properties of such models remain inadequately addressed, yet knowledge thereof is indispensable if one wants to prepare large, robust, and long-lived quantum spin liquids. Using large scale quantum Monte Carlo simulations we find a renormalized classical spin liquid which better explains part of the experimental observations than a quantum spin liquid. I comment on the adiabatic approximation to the dynamical ramps for the electric degrees of freedom, and the magnitude of the observed string parity order parameters.

Second, through combining the dipolar XY and Ising ZZ interactions, we predict the existence of a robust supersolid phase on the triangular lattice for 100s of particles based on explicitly calculated pair interactions for 87Rb and with a critical entropy in reach of current technology. Such a lattice supersolid is long-lived, found over a wide parameter range in an isotropic and flat two-dimensional geometry. It has true long-range order, even at finite temperature, thanks to the dipolar interactions, and would constitute a rare example of the defect-induced paradigm of supersolidity.

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Wednesday, April 9, 2025
Tao Wang (UMass Amherst)

New Techniques in Computational Quantum Field Theory: From Undergraduate Math to High-order Feynman Diagrams

Feynman diagrams serve as the visual language of quantum field theory, offering a powerful tool to describe phenomena across various physical systems. Computing these diagrams accurately is essential for predicting experimental outcomes and advancing theoretical understanding, yet remains remarkably challenging, particularly when exploring complex quantum many-body systems where higher-order effects become critical.

In this talk, I will demonstrate how mathematical techniques taught in undergraduate courses can be transformed into powerful computational tools that address frontier problems in quantum field theory. My recent work introduces two complementary approaches: an efficient representation for Green's functions—the essential building blocks of diagrammatic calculations—and a systematic method for organizing Feynman diagrams into compact computational graphs. These methods significantly enhance our ability to evaluate higher-order diagrams, opening new pathways to explore quantum many-body physics with unprecedented precision and computational efficiency.

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Wednesday, April 16, 2025
Rosa González (UNAM)

The relation between GC systems and SMBH in spiral galaxies: the link to the M• – M∗ correlation 

Abstract We explore the relationship between globular cluster total number, NGC, and central black hole mass, M•, in spiral galaxies. Including cosmic scatter, log M•∝ (1.64 ± 0.24) log NGC. Whereas in ellipticals the correlation is linear [log M• ∝ (1.02 ± 0.10) log NGC], and hence could be due to statistical convergence through mergers, this mechanism cannot explain the much steeper correlation in spirals. Additionally, we derive total stellar galaxy mass, M∗, from its two-slope correlation with NGC (Hudson et al. 2014). In the M• versus M∗ parameter space, with M∗ derived from NGC, log M• ∝ (1.48 ± 0.18) log M∗ for ellipticals, and log M• ∝ (1.21 ± 0.16) log M∗ for spirals. The observed agreement between ellipticals and spirals may imply that black holes and galaxies co-evolve through “calm” accretion, AGN feedback and other secular processes. 

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Wednesday, April 23, 2025
Tim Atherton (Tufts)

Shape optimization problems in Soft Matter 

An emerging theme across many domains of science and engineering is materials that can change shape, often dramatically. Shape may even be a programmable quantity, where local properties of the material may be adjusted to promote a desired morphology. Determining the final structure of such materials involves solving an optimization problem whereby a given objective functional, such as an energy, that promotes shape deformation must be minimized. Optimization with respect to both the shape of the domain and auxiliary fields describing the structure or quantities such as electromagnetic fields. Constraints may also be present, including fixing the volume or excluding the material from a particular region of space. The class of problems just described is very challenging to solve, and there is a lack of simulation tools that are both readily accessible and general purpose. For some materials, suitable numerical discretizations are emerging or even entirely missing. 

To help address this gap, I will present Morpho, an open-source programmable environment intended to facilitate solution of shape optimization problems and computational geometry more generally. I’ll demonstrate a range of emerging applications from different areas of soft matter physics: including contact mechanics, hydrogels, liquid crystals, membranes, and elastic filaments. Prospects for applying these methods to new materials, such as ferroelectric nematics and smectics, as well as methods for landscape exploration will also be described. 

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Wednesday, April 30, 2025
Daniel Haehn (UMass Boston)

Almost Tenured at UMass Boston: Six Crazy Years!

I will cover my time as a Computer Scientist at our beloved university and will tell you about 1. breast cancer research that led to powerful machines on our campus, 2. the blessing of my first phd student and her 4 papers, 3. how empowering students led to very successful undergraduate research, 4. the visualizing.boston course that led to the creation of the perfect grading infrastructure, and 5. other takeaways!

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Wednesday, May 7, 2025
Reuben Wang (ITAMP/Harvard)

Itinerant collisional spin dynamics with ultracold polar molecules

In this talk, I will discuss the prospects of utilizing ultracold gases of polar molecules for studies of itinerant spin dynamics. Such experiments are already achievable today, to which I will explain the theoretical models we developed that well describe recent measurements done at JILA [A. Carroll et al., Science (2025)]. I will also discuss several theoretical extensions and proposals for such itinerant platforms, paving a route toward unique explorations of quantum state resolved chemistry, and large scale entanglement dynamics in many-body systems. 

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Wednesday, May 14, 2025
No colloquium -- End of Semester