The Mass Shell of the Nelson Model without Cut-Offs

The massless Nelson model describes non-relativistic, spinless quantum particles interacting with a relativistic, massless, scalar quantum field. The interaction is linear in the field. We analyze the one particle sector. First, we construct the renormalized mass shell of the non-relativistic particle for an arbitrarily small infrared cut-off that turns off the interaction with the low energy modes of the field. No ultraviolet cut-off is imposed. Second, we implement a suitable Bogolyubov transformation of the Hamiltonian in the infrared regime. This transformation depends on the total momentum of the system and is non-unitary as the infrared cut-off is removed. For the transformed Hamiltonian we construct the mass shell in the limit where both the ultraviolet and the infrared cut-off are removed. Our approach is constructive and leads to explicit expansion formulae which are amenable to rigorously control the S-matrix elements.Comment: explanations added, typos correcte

COVID-19 Isolation: Daily Lessons

COVID-19 continually disrupts classroom structure, design, and the lessons being taught. A return to in-person, on-site classrooms is being challenged again by new variants and people’s desire to gather during holidays. Our goal as caring educators is to “educate rather than separate” as we “continue / To humanize / Our study / Of humanities.

Pandemic Paranoia and Proximity: A Transformation

COVID-19 has transformed the manner in which students are being educated. Social distance, sterilization, and remoteness have replaced teaming, personalization, and classroom proximity. Contact tracing stirs fears, often replacing creative writing and skill-building. Fear and separation have become commonplace

What If the Arts Were Taken Away?

The arts give clarity to their emotions, situations, questions, and lives. Students experiencing all the arts gain a comprehensive perspective. Lyndon B. Johnson observed: “(I)t is in our works of art that we reveal to ourselves and to others the inner vision which guides us as a nation.

A Post-Pandemic Perspective: Challenges, Choices, and Adaptations

This poem deals with the challenges of returning to an in-person experience after having faced the challenges associated with teaching in remote and hybrid classrooms during the pandemic

Evaluation of the burden of HPV-related hospitalizations as a useful tool to increase awareness: 2007–2017 data from the sicilian hospital discharge records

In light of the implementation of human papillomavirus (HPV) prevention strategies, epidemiological studies in different geographical areas are required in order to assess the impact of HPV-related diseases. The purpose of the present study was to describe the burden of HPV-related hospitalizations in Sicily. A retrospective observational study estimated 43,531 hospitalizations attributable to HPV from 2007 to 2017. During the observed period, there was a decrease for all HPV-related conditions with a higher reduction, among neoplasms, for cervical cancer (annual percent change (APC) = −9.9%, p < 0.001). The median age for cervical cancer was 45 years old, with an increasing value from 43 to 47 years (p < 0.001). The age classes with greater decreases in hospital admissions for invasive cancers were women aged 35 years or more (APC range from −5.5 to −9.86) and 25–34 years old (APC = −11.87, p < 0.001) for women with cervical carcinoma in situ. After ten years for vaccine introduction and sixteen years for cervical cancer screening availability, a relatively large decrease in hospital admissions for cervical cancer and other HPV-related diseases in Sicily was observed. Some clinical characteristics of hospitalization, such as increasing age, are suggestive clues for the impact of preventive strategies, but further research is needed to confirm this relationship