Following the pioneering work of Carl M. Bender et al. (1998), there has been an increasing interest in theoretical physics in so-called PT-symmetric Schr�dinger operators. In the physical literature, the existence of Schr�dinger operators with PT-symmetric complex potentials having real spectrum was considered a surprise and many examples of such potentials were studied in the sequel. From a mathematical point of view, however, this is no surprise at all – provided one is familiar with the theory of self-adjoint operators in Krein spaces.
Jan Nesemann studies relatively bounded perturbations of self-adjoint operators in Krein spaces with real spectrum. The main results provide conditions which guarantee the spectrum of the perturbed operator to remain real. Similar results are established for relatively form-bounded perturbations and for pseudo-Friedrichs extensions. The author pays particular attention to the case when the unperturbed self-adjoint operator has infinitely many spectral gaps, either between eigenvalues or, more generally, between separated parts of the spectrum.

About the Author

Dr. Jan Nesemann holds a master’s degree in mathematics as well as in business administration. He received his PhD in mathematics from the University of Bern under the guidance of Prof. Dr. Christiane Tretter. Currently he works as an actuarial and financial services consultant in Zurich.

"About this title" may belong to another edition of this title.

Store Description

Account dedicated to Print on Demand titles. Brook Bookstore offers a wide selection of books with a continuously updated catalog and fast shipments all over the world. We hold distribution rights with all of the publishers we promote and are in continuous search of new interesting titles to propose to our customers. We are part of Brandon Group SRL (an Italian company) and all of the orders are shipped from Europe. Depending on availability orders will be picked from our different warehouses. CONTACT US If you have any questions please do not hesitate to contact us sending a message to our store. We have a well prepared customer service team who will be happy to assist you. Our working hours are from Monday to Friday from 9:30 to 18:30 (CET, UTC +1) so messages received during the weekends might be responded with a slight delay but we guarantee you will get back to you as soon as possible. RETURNS If you want to return your order, please submit your request through Abebooks platform. Returns requests are managed case by case by our team and always in line with Abebooks policies: AbeBooks? Return Policy guarantees that you can return any book for a refund within 30 days, when the return is due to an error on the bookseller?s part. When the motive of the return is not due to an error of the seller it is up to Brook Bookstore to accept the return or else after studying the case. CANCELLATION You can send a cancellation request to our customer service team while the package has not yet been shipped. After that we cannot ensure we can retrieve the parcel but we suggest you to get in touch with us in order to verify the case. INVOICE You can request the invoice to be issued together with the shipment of the order or, at the latest, in the same month of the shipment.

Visit Seller's Storefront

Seller's business information

Brandon Group S.R.L.
Via Vannella Gaetani 27, Brandon Group, Napoli, NA, 80121, Italy

Sale & Shipping Terms

Terms of Sale

Account dedicated to Print on Demand titles.

CANCELLATION
You can send a cancellation request from the order page while the package has not yet been shipped. After that we cannot ensure we can retrieve the parcel but we suggest you to get in touch with us in order to verify the case.

INVOICE
You can request the invoice to be issued together with the shipment of the order or, at the latest, in the same month of the shipment.

RETURNS
If you want to return your order, please contact us for authoriz...

More Information

Shipping Terms

Shipping rates from Italy to U.S.A.

Shipping rates from Italy to U.S.A.
Order quantity	25 to 40 business days	60 to 60 business days
First item	US$ 4.63	US$ 591.03

Delivery times are set by sellers and vary by carrier and location. Orders passing through Customs may face delays and buyers are responsible for any associated duties or fees. Sellers may contact you regarding additional charges to cover any increased costs to ship your items.