GUPEA

Gothenburg University Publications Electronic Archive

GUPEA is a platform for e-publishing of theses, student essays and other research publications.

Recent Submissions

  • Johan Ludvig Runebergs efterlemnade skrifter Bd 1
    (1878) Runeberg, Johan Ludvig,
  • Selmer group actions on p-adic automorphic cohomology
    (2026-05-12) Molin, Douglas
    This thesis studies connections between Galois representations and automorphic forms, two central objects in modern number theory. In contrast to the classical setting of modular forms, the Hecke eigenspaces in automorphic cohomology of the general linear group over a CM field are spread out across multiple cohomological degrees. In the p-adic setting and under technical hypotheses, we explain this phenomenon by equipping such eigenspaces with actions of their associated dual adjoint Bloch-Kato Selmer groups, thereby establishing new cases of a conjecture of Venkatesh. Appended to the thesis are two articles: In Article I we treat the special case of PGL_2 with p a totally split prime. Under various hypotheses, we construct an action using the p-adic local Langlands correspondence for GL_2(Q_p) and completed homology. The main result is a `big R=T' theorem in characteristic 0, proved via a Taylor-Wiles patching argument, from which the Selmer group action is obtained in a natural way. In Article II we consider the general case of \GL_n. Under mild assumptions, we define a Selmer group action using derived Galois deformation rings and the extension of the Taylor-Wiles method, building on previous work of Galatius--Venkatesh. We also establish an equivalence between the derived deformation ring of rho and the completion at the point corresponding to rho of the derived deformation ring of its mod p reduction, thus generalising frequently cited results of Kisin.
  • Temporomandibular Disorders in Head and Neck Cancer: Risk Factors, Patient Perspectives, and Strategies for Prevention
    (2026-05-12) Saghafi, Ellie
    Abstract Treatment of head and neck cancer (HNC) includes radiotherapy (RT), chemotherapy, and surgery and may impair functions resulting in orofacial pain, oral dysfunction, and impaired quality of life. Despite this, few studies describe temporomandibular dysfunction (TMD) and possible prevention in patients treated for HNC. Aim: The overall aim is to improve the understanding of patient experience and to investigate the prevalence, possible risk factors, and outcome of preventive exercise for TMD in patients with HNC. Material and method: In Study I, patients with oropharyngeal tumors were included retrospectively (n = 217). TMD prevalence before oncological treatment and at 6- and 12-months posttreatment were assessed. Study II, a qualitative interview study, included 10 HNC patients post treatment. Data analysis was based on qualitative content analysis. Studies III and IV are based on a prospective and randomized controlled trial with HNC patients (n = 58) randomized into either control or intervention groups before oncologic treatment with a one-year follow-up. Intervention consisted of preventive daily jaw-exercise during radiotherapy. Patients were followed using both objective measurements (Diagnostic Criteria for TMD) and validated questionnaires. Results: Study I: Symptoms of TMD increased 12 months post-RT. Possible factors affecting the increase in TMD symptoms were brachytherapy, mouth opening prior to treatment, self-reported depression, and overall health status. Study II: The results provided a variety of post-treatment consequences, both physical, cognitive, and social. Themes such as emotions and coping strategies both before and after cancer treatment were revealed, indicating a need for a more individually designed approach, support, and rehabilitation. Study III showed that preventive jaw-exercise effectively preserved maximal inter-incisal mouth-opening (MIO) and prevented the development of myalgia both at 6 and 12 months post RT. Study IV confirmed that jaw-exercise helps to protect against decline in MIO and the development of myalgia. A TMD diagnosis at baseline was identified as a risk factor for post-treatment myalgia, whereas no other significant baseline predictors of TMD development were found. Conclusions: TMD-symptoms are common after RT for HNC patients and are perceived to negatively impact daily life. Jaw-exercises before and during RT may help prevent the development of TMD. Keywords: Head and neck cancer, prevention, temporomandibular disorders, predictive Temporomandibular disorders (TMD); head and neck neoplasms; radiotherapy; Symptoms.
  • Partition functions in algebraic geometry
    (2026-05-12) Andreasson, Rolf
    In geometry, a common theme is to construct canonical objects or invariants related to a given geometric object. For complex projective varieties — defined by polynomial equations over the complex numbers — this is exemplified by the hunt for canonical Kähler metrics. Past and recent progress has connected the existence of various canonical metrics with intricate, but algebraic, stability conditions of the underlying variety. For an arithmetic variety — a scheme defined by polynomial equations with integer coefficients — one can define its height, roughly measuring its arithmetic complexity, in terms of Arakelov geometry and with respect to a metric over the corresponding complex projective variety. When the metric is taken to be canonical, one obtains an invariant, its canonical height. These notions are studied in this thesis from the perspective of a canonical statistical mechanical system — an N-point process in the form of a Gibbs measure for a certain interaction energy — defined on either a Fano or a canonically polarized variety. In the canonically polarized case, the canonical Kähler–Einstein metric with constant negative Ricci curvature has been shown to emerge in the large N-limit. Given a statistical mechanical system, a lot can be learned from studying its \emph{partition function}. In the large-N or thermodynamic limit, the same role is played by the systems free energy. The thesis consists of five papers exploring this direction. In the first two, a sharp height bound is conjectured for arithmetic Fano varieties whose complexifications are K-semistable, in analogy with K. Fujita's bound over C. In Paper I this conjecture is established for the canonical integral model of a toric Fano manifold of dimension at most 6. The general case is shown to hinge on a conjectural gap hypothesis for the degree, recently established by Li–Miao. Paper II establishes the conjecture for diagonal hypersurfaces, and orbifold curves. The conjecture makes contact with Kähler–Einstein metrics, K-stability, and the aforementioned canonical height, coinciding with a version of the free energy. In Paper III, canonical heights are studied for Fano and canonically polarized arithmetic log pairs. Here the full statistical mechanical approach is leveraged to give a limit formula in terms of periods for the canonical height. It is valid in the canonically polarized case, and in the Fano but K-stable case in dimension one. Several applications are drawn from this result: an explicit formula in the case of log pairs consisting of the projective line with three points; based on an explicit period-formula originating in conformal field theory. Explicit formulas for the height of some Shimura curves; which combined with a recently established related height formula by X. Yuan yields information on the canonical integral model of some Shimura curves. Finally, an explicit formula for the canonical height of a Fermat curve. Paper IV takes a slightly different perspective. A general Coulomb gas on the sphere is studied, which in a special case coincides with the aforementioned system in case of the projective line. Instead of using a statistical mechanical framework to study problems in algebraic, Arakelov and Kähler geometry, methods of algebraic geometry are used to study problems in mathematical physics regarding this system. Among the results are a formula for the critical temperature at which the partition function diverges and asymptotics for the Gibbs measure and partition function as the critical temperature is approached. Some applications to well-studied versions of the systems, such as the two-component plasma, are given. In Paper V, the statistical mechanical approach is extended to the case of Fano manifolds with non-discrete automorphism group. While the large-N limit is still conjectural, just as in the higher-dimensional Fano case in general, several applications of the introduced framework are obtained. In particular, a notion of Gibbs polystability is defined in terms of log canonical thresholds of certain canonically defined divisors, refining the notion of Gibbs stability, and ensuring the existence of the statistical mechanical system for N large. Conjecturally, Gibbs polystability should by equivalent to the existence of a Kähler–Einstein metric, and the large-N limit of the thresholds for Gibbs polystability should coincide with an analytic coercivity threshold, yet to have been shown to equal an algebraically defined invariant. We compute all these invariants and verify the latter conjectures for log Fano curves. This in turn yields applications to a sharp and improved logarithmic Hardy–Littlewood–Sobolev inequality on the 2-sphere for probability measures with vanishing barycenter. Lastly, the limit period formula for the canonical height is extended to the case of K-polystable log Fano curves with non-discrete automorphism group.
  • Characterization of Multimodal Preclinical Imaging Systems
    (2026-05-11) Jelander, Agnes; University of Gothenburg/Institute of Clinical Sciences; Göteborgs universitet/Institutionen för kliniska vetenskaper
    Background A setup of four compatible imaging systems for small animal from Bruker has been delivered to Sahlgrenska Academy at University of Gothenburg and Sahlgrenska University Hospital, and forms the basis of SBIC (Sahlgrenska Bioimaging Center). The aim of the study was to characterize the performance of the positron emission tomography (PET)system and computed tomography (CT)system at SBIC as well as the dose calibrator and two radiation protection instruments, but also to analyse two methods of attenuation correction using either data from CT or magnetic resonance imaging (MRI). Method The response of the dose calibrator was characterized for geometric factors and activity dependence using 99mTc, 177Lu, 131I, 125I and 18F sources. The PET-system was characterized by measuring the sensitivity, correction factors, linearity, highest and lowest measurable activity, scatter fraction, spatial resolution, uniformity and recovery coefficients using various phantoms filled with 18F-FDG (fluorodeoxyglucose). To characterize the CT-system three protocols, two reconstruction algorithms, uniformity, spatial resolution and noise were measured using two phantoms. CT- and MRI-based attenuation correction of PET images of a tumour bearing mouse injected with 68Ga-DOTATOC was analysed by comparing the activity concentrations in various tissues. Two radiation protection instruments, Berthold LB 122 and 124, were characterized by examining the linearity and minimum detectable activity for two phantoms containing 131I. Results Using the dose calibrator, a linearity was identified for all radionuclides, the suggested working region was 2-8 cm, larger uncertainties were found for smaller volumes, and a radionuclide dependence was identified. The sensitivity of the PET-system varied with activity, however, a linear correlation was identified with enlarged uncertainties for lower activities. Best uniformity and resolution were achieved from the image without attenuation correction. Highest and lowest measurable activity was 41 MBq and 0.1 MBq, respectively. The CT-system achieved the lowest variation of Hounsfield units (HU) when using the high-resolution protocol, but the resolution was similar for the high-resolution and the generalpurpose protocols. The CT-attenuation correction of PET images resulted in higher activity concentration than MRI-attenuation correction. A linear response was identified for both radiation protection instruments for each measurement setup. The minimum detectable activity was estimated to 35 kBq at 10 cm distance using Berthold LB 122. Conclusions The dose calibrator is appropriate to use under the suggested working conditions. Essay/Thesis: 30 hp Program and/or course: Medical physics Level: Second Cycle Term/year: Fall 2025 Supervisor: Eva Forssell-Aronsson, Hana Bakr, Johan Spetz, Lukas Lundholm, Mikael Montelius Examiner: Magnus Båth Keywords: Preclinical imaging, Multimodal, Characterization, small animal PET, micro-CT, MRI attenuation correction, Bruker, Molecubes 3 The sensitivity of the PET-system, calculated in the software PMOD, was activity dependent. The system had a resolution of at least down to 2 mm and the measurable 18F-FDG activity range was 0.1- 37 MBq. For the CT-system, the Feldkamp, Davis and Kress (FDK) algorithm with helical acquisition was less good and the image space reconstruction algorithm (ISRA) should be usen when quantification is needed. The MRI-based attenuation correction method evaluated underestimated the activity concentration compared with CT-based attenuation correction and needs to be improved. Altogether, the PET- and CT-systems were well characterized, but further studies on phantoms and animals would be interesting and give more information. The two radiation protection instruments worked well.